Transcript of Dr Sarah Berry on The Diary Of A CEO

Now, by processing, it could be our own processing. When we chew a food, we change the structure. Take a nut, for example, you have a whole nut, you chew it, you break up the nut, it goes into your gastrointestinal tract, it’s broken down further. We also change it using manual industrial techniques as well. So we use techniques like grinding, or we might use pasteurization for dairy, or extrusion for some carbohydrate-rich foods. We use all of these different techniques that also change the food matrix.

STEVEN BARTLETT: It’s better or for worse?

DR SARAH BERRY: It’s a double-edged sword. Right. And I think this is what we need to remember, that everyone’s demonizing at the moment. Ultra-processed food, you know, it’s killing the nation. 60% of our energy is coming from ultra-processed food. Yes, we are eating too much unhealthy food, much of which has been heavily processed, but processing can also be used to our benefit.

And we have to think, why do we even process food in the first place? Well, we process it to make it edible. I don’t want to go and eat a rice grain that’s not been cooked. We make it safe. I want to drink pasteurized milk because I know it’s safer. We want to make it stable. I think how long a can can last and frozen vegetables versus fresh. So you’re saving food waste. We want to make it taste good, and we want to make it convenient.

There’s all of these different reasons that we use food processing, but when we think about the healthfulness of a food, we need to think about it in terms of the processing techniques that have been used, as well as the nutrient composition. We can’t look at them in isolation, in my opinion. And this is what I’ve done a lot of research looking into.

STEVEN BARTLETT: And what is processing gone bad?

DR SARAH BERRY: I think processing gone bad is when you change the nutrient profile of a food such that it is unhealthy. So in simple terms, it’s too much saturated fat, too much salt, too little fiber, too little bioactives like polyphenols, a food that is very energy dense. You eat it really, really quickly. If you’re eating too many calories, you’re eating it before your hunger signals have got to your brain and say, well, Stephen, you’ve had enough.

And there’s great research that has been looking at how processing can affect your eating rate, the energy density of food, the nutrient profile of a food. And that’s where it can go wrong. But where it can go right is you can improve all of those things I’ve said, the stability, the safety of the food. You can also increase the, what we call bioaccessibility. So the availability of some of the nutrients within a food as well.

Analyzing Different Snacks

STEVEN BARTLETT: Okay, so I’ve got some snacks over in the corner of the room here, which I guess have been processed differently to have a different impact on me as the consumer. Gosh, these look delicious. I hope they’re salt and vinegar Pringles. Are you going to eat them?

DR SARAH BERRY: Oh my gosh.

STEVEN BARTLETT: So I’ve got some mixed nuts here. I’ve got some cookies, some little pieces of chocolate and some crisps. So you were talking about this processing something so that I eat it faster and that it doesn’t like sort of satiate me or make me feel hungry. Crisps. We’re a nation of crisp lovers. When you were saying that about something that makes you eat fast and not realise that you’ve even eaten it all, crisps were the first thing that came to mind for me.

DR SARAH BERRY: I love a crisp. You love a crisp. We all love a crisp. So I think all of these first three foods, the crisps, the chocolate, the cookies, you know, if compared to what would be a healthy food, they’ve all got less fibre. They’ve all got, well, certainly that the chocolate and the cookie has got more sugar. They don’t have all of the wonderful bioactives in them. And then with the crisps, depending on the type of crisps, it’s probably quite high in salt.

But the chances are with those three is that they are quite energy dense. So they have quite a lot of calories per gram, which is partly because of the processing techniques. Yet if you take a whole food like a nut, now they’re actually very energy dense. So they’re very high in fat. They’re high in calories. But actually, because they’re in their original food matrix, how your body handles them is quite different to if, for example, they have been processed.

STEVEN BARTLETT: You mentioned something about my brain takes a little while to figure out that I’ve started eating. So if I started smashing these crisps down now, how long would it take my brain to realise that I’ve started eating to sort of catch up and make me feel hungry?

DR SARAH BERRY: Yeah. So there’s lots of different mechanisms that impact how full we feel, how hungry we feel related to a food. There’s different hormones that are released from different areas of our gut, for example, that feedback signals to say either you’re full or you’re hungry. On average, I would say it takes about 10 to 20 minutes for the fullness to really properly kick in.

STEVEN BARTLETT: Now you could easily have got through those. Well, I could easily have got through all of these under that 20 minutes. I wasn’t aware that there was a delay, but it does make sense because there’s certain foods that I used to eat, like Pringles and snacks and crisps and things like that, where I feel like I could eat two tubes of the thing before my body even realised what was going on. And are they in some way designed to encourage that speed of eating?

DR SARAH BERRY: So there are many people who will say the food industry has specifically designed these to make them firstly, what we call hyper palatable. So to have the right mix of fat, sugar, you know, carbohydrate, et cetera, to make them really tasty. And in this case, salt as well. I don’t think the food industry is out there to get us. I think that what the food industry was doing 50 years ago versus what they’re doing now is quite different. But some people will say I’m very naive. I do believe the food industry ultimately want to produce food that’s safe, but also healthy for us. That’s probably an unpopular opinion, but based on my interactions with the food industry, I believe that.

However, I do believe that these crisps are there, have been made to be flavoursome, to be palatable to you, so that you do enjoy them. Now, whether that’s that you then go and overeat them, I think is, yes, a by-product of that. Now, it doesn’t take 20 minutes for all of the fullness signals to kick in, because as soon as you start chewing something, you start to release different hormones and different sensory characteristics of the food will also trigger some sort of fullness. But what we do know is that you have more of these fullness receptors saying, hey, you’re full, lower down in your gastrointestinal tract.

The Importance of Eating Slower

DR SARAH BERRY: And so if you can get food to the lower gastrointestinal tract, that’s when it says, hey, Stephen, you’re full now. And these heavily processed snacks that you’ve got here would be typically a sort of tire up the gastrointestinal tract, because kind of the hard work’s been done. And yet when you’ve got something like a whole grain or a nut, typically that would be a sort of lower down the gastrointestinal tract, where you’ve got more of these fullness signals, so giving you that greater feeling of fullness.

STEVEN BARTLETT: My girlfriend has said to me for many, many a year that I need to eat slower. And I thought it was like a spiritual thing that she’s into, to do with like giving the food gratitude, et cetera, et cetera. But upon reading your work and having this conversation today, now I’m starting to believe that she was right all along, unsurprisingly, once again, and that there is a scientific basis for slowing down how fast I eat.

DR SARAH BERRY: Absolutely. We now know that eating rate is important. There’s some fantastic work that’s being done by a professor, Karen Ford, who’s dedicated many years into researching this and looking at how changing the structure and texture of the food can modulate your eating rate, and how also your eating rate can modulate how you metabolize the food and how many calories you go on to eat. And so it’s a great example. You know, I talked about all of these different pieces of the puzzle. That’s one of those pieces.

So when we talk about how you eat, changing your eating rate, so how quickly you have your breakfast, your lunch, your dinner, or any of these snacks, will also, without you consciously thinking about it, change how many calories you eat, might change how quickly you metabolize the food as well.

STEVEN BARTLETT: What’s the sort of knock-on effects there?

DR SARAH BERRY: So the research that’s been done by Karen Ford shows that, on average, if you change the speed in which you eat your food by about 20%, you reduce your calorie intake by about 15%. And that’s due to where you’re releasing your hunger hormones, how many hormones you’re releasing, etc.

So it’s a really simple strategy. And we see this play out as well, even in our own evidence. When we look in our ZOE predict studies, that’s fast eaters versus slow eaters, we see that once we adjust for lots of other confounders, there’s a difference of 120 calories between what fast eaters have over a day versus slow eaters, with the fast eaters eating more calories compared to slow eaters.

And there’s even been clinical trials where they get groups of individuals and say, okay, slow down the rate at which you eat your food. Over the next three, four, five weeks, they have another group that say, just eat at your normal rate. Those people who are intentionally slowing down the rate at which they eat their food lose more weight than those people who continue to eat at their normal rate.

STEVEN BARTLETT: See, I always made this weird, unfounded evolutionary argument to her. I was like, well, you know, in the wild, you’ve got to eat what you can, so people eat quick. But we’re not in the wild anymore, and the food choices that we have are drastically different now.

DR SARAH BERRY: Yeah, and also the food that is available to many of us is the kind of food that can be eaten really quickly. So there’s some great research that’s been conducted that shows that heavily processed, soft textured type food can be eaten 50% more quickly than the unprocessed, harder textured equivalent. So the kind of food that we’re eating now is quite different. So you’re eating it really quickly. You’re overeating because your hunger signals haven’t got there, but it’s that rate at which you’re eating.

STEVEN BARTLETT: What’s an example of a soft textured food versus a hard textured food?

DR SARAH BERRY: So we can use an example from a study that was actually conducted in 1977, and this was published in The Lancet. It was one of the first nutrition studies published in The Lancet, and it’s one of the first studies to show the importance of the food matrix, and it kind of got buried for many years. And it’s a study by a scientist called Haber where he fed individuals whole apples. He fed individuals the equivalent amount of carbohydrate from apple puree. It was exactly the same, i.e. same nutrients, same fiber, same everything else in it. All that’s different is the apples are hard, the puree is soft.

And what he found was that those people who were given the puree, even though they were given exactly the same amount of calories, ate that puree, or rather drank that puree, three to four times more quickly than when they had the apples, the equivalent amount of calories. So they were eating the same amount of calories, but three to four times more quickly.

STEVEN BARTLETT: That’s like 300%, 400% faster.

DR SARAH BERRY: They felt less full, so when they measured their fullness, and they monitored that for quite a few hours, so going up to quite a few hours, those that were having the apples continued to feel full for longer. Those that were having the puree didn’t feel full for long.

And what also happened, interestingly, is those that were having the puree had what we call a blood sugar dip. So about two to four hours after having a high-carbohydrate meal, we know that some people have a dip in their circulating blood sugar. And we know from our own theory of predict research that actually this can really increase your hunger levels. And so we know from our research, if you are a dipper, I’m a dipper, hence I get hungry quite often.

So in about two hours I’m going to be eating one apple. If you’re a dipper, your blood glucose is going below your baseline levels. And so you get hungry, you go on to eat 180 calories on average more at your next meal because of that.

This research from 1977, I think it’s fascinating. It’s that first research really demonstrating the importance of food matrix. And then since then, I’ve now, over the last 10 years, done lots of studies with nuts, with oats, for example, that demonstrate you can have two foods that have identical backpack labelling, identical nutrients, identical calorie value, if you were to look at the backpack labelling, but can have entirely different impacts in terms of how much energy you absorb, how you metabolise that food, how it impacts your hunger, how it impacts downstream health effects.

Research on Nuts and Food Matrix

STEVEN BARTLETT: And you’ve done some research on walnuts, right?

DR SARAH BERRY: So we’ve done work on walnuts, but particularly on almonds. So we’ve done lots of work with almonds using it as a kind of proof in principle of the importance of the food matrix. Now, you just took a bite of that and I could hear the crunch. The reason I could hear the crunch is because in almonds, like most nuts, like many plant-based products, there is a very rigid cell wall.

So that almond that you’re holding there has thousands and thousands and thousands of cells. These cells are tiny. They’re about 50 microns. You can’t see them with the human eye. I can show you a micrograph. But there’s thousands in there. Now, each of those cells is smaller than a grain of sand. And each of those cells, cell walls, is encapsulating the fat. So we know that in most of these nuts, they’re about 50% fat. Hence, people say, oh, my gosh, I can’t eat nuts. They’re high fat. They’re high calorie.

Now, in all of those nuts, the fat’s encapsulated in this rigid cell wall. When you bit that, you fractured some of those cell walls. When you swallow it, you chewed it. You chewed it a little bit, I assume.

STEVEN BARTLETT: A little bit. Yeah, I didn’t swallow it.

DR SARAH BERRY: When people chew it, we know from these lovely chew and spit studies or mastication studies that we do that at the point at which you swallow a nut, the particles, i.e. the size of the bits that you’re swallowing that you’ve chewed, are about maybe half a millimetre to one millimetre in size.

Now, given that the cell of an almond nut is about 50 microns, that means when you’re swallowing, within that, what we call a macroparticle, you’ve still got thousands of cells. They’re intact, where you’ve got this lovely cell wall containing all of this fat. And so you’re swallowing these intact cells containing, encapsulating the fat. So they’re what we call very low bioaccessibility. They’re not very accessible to us, this fat.

Now, what happens is, as part of your gastrointestinal tract, some of the enzymes can break down the cells a little bit, but actually a lot just comes out the other end. So I don’t know whether you’ve ever eaten a bag of nuts and looked at your poo after.

STEVEN BARTLETT: None of your business.

DR SARAH BERRY: Go and do that. But you should see some almond particles. When I’m being a mum, when I’ve looked at a lot of poo in my life, through my work but also through being a mum, you can see whole nut particles in the poo.

STEVEN BARTLETT: So nuts, they just don’t break down fully?

DR SARAH BERRY: So they break down partially. So you break down about 10% in the mouth before you swallow. So about 10% of the calories become available because the calories are contained from the fat, etc. And then you probably break down about another 60% to 70% as it passes through your stomach, your small intestine and your large intestine.

But you have loads of material arriving at your colon, which is your large intestine, that’s undigested, which is good for two reasons. One, because you’re giving all of this food to your microbiome, which we know is great for your health. Your microbiome is having a party with these nuts. But also, if you are worried about eating nuts because of their high calorie value, actually 20% to 30% of the calories are just coming out the other end.

But where it gets really interesting is if we then take exactly that nut that you’re holding there, and if I was to industrially grind it so that I broke all of those cells’ walls, so we’re breaking it down to less than 50 microns so that you’re releasing all of the fat. So it becomes 100% bio-accessible, i.e. you absorb 100% of it.

But they could have two identical back-of-pack labels because they’re the same ingredient. All that’s happened is you’ve ground that nut to such an extent that you’ve released everything. And so having that in its whole form is beneficial because if you are concerned about energy intake, it’s reducing the energy. It’s providing this amazing food for your gut microbiome. It’s changing also how your blood changes metabolically in that about eight hours after eating it. And this is what I’ve done lots of work on, looking at how your blood fat increases and decreases in that immediate period after eating either ground nuts or whole nuts.

But once you grind it, I’m not saying it’s necessarily bad because the upside of that is all of the other good nutrients contained within that cell, like the vitamin E and some of the other components also become available so it’s this double-edged sword. But that’s what I think is so fascinating about processing and about food matrix and why we have to move on thinking about food just in terms of the nutrients because you can have two foods with identical back-of-pack labelling that have different effects.

Research on Oats and Food Processing

DR SARAH BERRY: And we’ve seen the same with oats. We’ve been doing studies as well where we feed people large oats, like the steel-cut sort of old-fashioned porridge, or you feed people finely ground oats. And so we’ve done clinical trials where, on one occasion, people come in and they’ll have 50 grams of carbohydrate for breakfast of these large oats. Then they’ll come in another day and they’ll have exactly the same oats where we’ve ground them.

Literally, we’ve got students just grinding them down so they’re more like a powder. And the difference in the metabolic response in that following six hours after having either the large traditional oats or these finely ground oats is enormous.

STEVEN BARTLETT: And that’s because of gut absorption speed?

DR SARAH BERRY: Yes. So with the nuts, what we’re seeing here is a difference in the amount as well as the speed. With the oats, what we’re seeing is a difference in the speed. So we’re seeing a difference in the rate because we know that the food matrix impacts the amount, i.e. with the nuts, the rate, i.e. with the oats, as well as where the food’s absorbed in the gut.

And so you see about a 40% difference in the postprandial glucose response. So this is the increase in circulating blood glucose after you’ve had these oats. We see about a 50% higher response from the ground oats versus the large oats. And that has subsequent impacts on hunger hormones, fullness hormones, insulin release, et cetera, et cetera.

STEVEN BARTLETT: And what role does fiber play in this? Because fiber’s becoming quite popular now. We’re seeing it in drinks and stuff like that. And there’s some candy in America when we were recording over in New York which had like 15 grams of fiber added to this candy.

DR SARAH BERRY: So fiber’s a really interesting one. And it’s a really interesting one because we know we’re not getting enough fiber. So we should be getting at least 30 grams of fiber. In the UK, and it’s similar in the US, we get on average about 20 grams of fiber. 95% of us are not having enough fiber.

So fiber is the one nutrient that we know consistently is associated with beneficial health effects, reduction in many cancers, reduction in cardiovascular disease, reduction in levels of obesity, type 2 diabetes, et cetera. It’s an amazing nutrient, fiber, and we don’t get enough of it.

STEVEN BARTLETT: Just to pause there then, why is it so good for us? Because it sounds like a super molecule the way you just described it.

The Benefits of Fiber

DR SARAH BERRY: So it’s good for us for many different reasons. And there’s loads and loads of different types of fiber. And the different types of fiber are good for us for slightly different reasons. Really simply put, we’ve got soluble fiber, and that’s great for us because it impacts things like cholesterol absorption as well as other factors related to how quickly we metabolize food, et cetera.

Then you’ve got insoluble fiber, which is the kind of fiber that, for example, are in those nuts because fiber in those nuts is actually the cell wall. So most cell walls of plants are just fiber. That’s great for us because it’s food for our microbiome. It helps bulk out our stool, so it reduces our transit time, how quickly our poo basically passes to our colon, reduces the risk of colon cancer and so forth.

But largely because it is the food upon which our microbiomes have their party, produce all of these wonderful molecules that we know impact so much related to our health. But we don’t get enough of it. And we don’t get enough of it because we’re not eating the right types of food that we have in high amounts. So having any kind of fiber is going to improve our health.

Having fiber that’s added artificially back into food is going to be better than having no fiber. So the kind of bars that you’re talking about that say are added fiber, great. Having fiber, though, from the whole food is always going to be better. And so with nuts, fiber is essentially the cell walls of the nuts.

So it’s having that role in reducing that bio-accessibility that we talk about at slowing those nuts down. So that’s always going to be better, having that fiber in the whole food, in its original structure, in the way nature intended. But having any kind of fiber is better than having none. And in a nation or many nations where we’re not having enough, if we can get some in our diet, even if it is processed fiber, it’s better than no fiber in my opinion.

STEVEN BARTLETT: One of the big revelations in my household has been just getting some of these bad snacks just out the house and replacing it with healthier whole snacks. And I say that because sort of the very definition, the very like sort of use case where we snack is when we typically don’t have a lot of time, where hunger kind of crept up on us in between a meal. And so we make fast decisions. It’s not a very considered decision.

And I was reading that there’s been some studies done where they took sort of two groups and gave them typical snacks versus healthy snacks, and they found a pretty significant reduction in cardiovascular disease.

The Impact of Snack Choices on Health

DR SARAH BERRY: Yeah, so this is one of my studies. And we looked at how changing people’s snacks can impact their health. And the reason we’re interested in this is because we’re a nation of snackers in the UK, as in many countries.

So we know that about 25% of our energy comes from snacks. That’s phenomenal. And so what we wanted to do is look at if we do a really simple snack swap, can we improve people’s health? And so we asked people to change 20% of their energy from either having typical UK snacks or having 20% of their energy from almond nuts for six weeks.

And then we looked at various health outcomes at the beginning of that six weeks and then at the end of that six weeks. We said keep everything else the same. We provided all of these snacks to them. We provided the typical UK snacks.

We spent a lot of time designing these. So we did lots of research where we looked in the UK, and it’s very similar in the US, what are the typical snacks? So basically we designed these muffins that ultimately were having a bit of a potato chip or crisp, a bit of a chocolate biscuit, a bit of a cake, just like imagine all put in one muffin. I mean, we didn’t go and get those and just stick them in one muffin.

But we worked out what’s the nutrient profile in the UK, in the US that comes from snacks. And then we designed a snack product that was quite highly processed that reflected that nutrient profile. So it’s quite high in saturated fat, high in sugar, high in refined carbohydrate, low in fiber. People had to eat 20% of their energy from these muffins, which my kids loved, or 20% from the almond nuts.

At the end of that, we measured lots of health outcomes, one of which was a particular measure that we do to look at people’s vascular function, so their blood vessel function. It’s a measure called flow-mediated dilation. It tells us in really simple terms kind of how healthy the blood vessels are. And what we found was the improvement in blood vessel function following having almond nuts versus having typical UK snacks equated to a 30% reduction in cardiovascular disease.

STEVEN BARTLETT: That’s crazy. In what period of time?

DR SARAH BERRY: Six weeks.

STEVEN BARTLETT: In six weeks.

DR SARAH BERRY: And do you know what I think is really interesting about this? It’s one simple, single dietary strategy. And snacks are under our own control, typically. What I have as a snack isn’t determined by my fussy kids. What I have as a snack quite often isn’t determined where I am at that point in time because I can bring my snacks with me. It’s a really simple, single dietary strategy that can have a big size effect, and I think that that’s really important.

It is really important, though, Stephen, at this point that I do say that I have actually had funding from the Almond Board of California, and they did fund that study. Although the way we conduct our RCTs, the funders have no impact over the study design, or they don’t get to see the raw data or the paper before we’re publishing it. But I just think it’s always important to declare conflicts of interest. We’ve seen this, though, play out in other studies with other nuts or other snack substitutes. So it’s not unique just to almonds. It’s a great illustrator of how changing our snacks can improve our health.

Snacking Habits and Their Impact

STEVEN BARTLETT: We really are a nation of snackers. You highlighted one of the stats there that in the U.K. and in the U.S., about 25% of our energy comes from snacks. Seventy-five percent of the energy that’s coming from those snacks is coming from unhealthy snacks. This was taken from the ZOE podcast.

In Mediterranean countries, only 14% of energy comes from snacks, which is half of the U.K., and 85% of British people report snacking compared to 10% in France. And in the U.K., we have 2.5 to 3 snacks per day, which translates to six or seven eating events a day. And this has massive impacts on our glucose spikes and drops throughout the day, causing metabolic chaos.

And that’s part of what I was thinking as I was thinking about this, is if I’m eating that muffin that you made, which resembles the sort of typical British composition of a snack, it’s not necessarily just that that snack is going to impact me. It’s that my next food choice, because I ate that snack, is going to be different, because I might be on a glucose rollercoaster here. So I might end up making a worse food choice thereafter, which then might impact maybe my sleep, because I’ve got a little bit of sugar in me when I’m settling down to go to sleep. And is there the sort of downstream domino effect because of that one snack choice?

DR SARAH BERRY: So I wouldn’t say that you’ve made one bad snack choice and that’s it. Your day’s over, damn it. You’re stuffed. I think that you highlight an important point, though, that what we choose as a meal does have knock-on effects on what might happen later in the day. So, for example, if you have a really refined carbohydrate breakfast or snack, then you’re more likely to have a blood sugar dip, which we know from our research is more likely to make you more hungry, eat more calories, have lower mood, have lower energy and be less alert.

But I think snacking can be used to our advantage. Snacking can be used to our advantage because we know it accounts for such a huge proportion of our energy intake, because we know on average that 70-75% of the snacks that we do come to eat in the UK and the US are not healthful snacks, and because we know that actually just transitioning from those to healthy snacks can have a big impact.

But I think it’s really important to be thinking about not just the type of snacks you’re having, but the time of day that you’re having the snacks. We published some research recently where we looked in 1,000 individuals with people’s snacking habits, because it’s not actually been looked at much. You’d think everyone snacks. You’d think there’d be loads of science out there about snacking. There’s lots of science out there about the different foods that we might snack on, but not really much looking at snacking habits.

There’s a lot of controversy out there about whether we should be grazers, and we are a nation of grazers. Well, I certainly graze, but many people we know, like you said, 80-90% of people do have multiple eating events throughout the day.

STEVEN BARTLETT: Are you taking these away from you for self-control?

DR SARAH BERRY: I am a little bit, yes. I think the smell of the chocolate and the cookies is testing me. In January, I’m not trying to be tested. There we go.

What we have never really fully understood is, is snacking per se bad? Are you having multiple eating events, so eating six times a day, which we nearly do in the UK and the US? Or is it about the type of food we’re snacking on? Should we revert back to having the three main meals, the breakfast, the lunch, the dinner? Or is it okay to have multiple meals as long as it’s healthy food?

So we looked at this in our cohort of 1,000 individuals, where we take lots of measures related to what they’re eating, when they’re eating, how they’re eating it, as well as lots of different health outcomes. And what we found was that the frequency of eating within reason was not a problem. So if people were grazing, having multiple eating events, as long as they were eating healthy foods, it didn’t matter having multiple eating events. So snacking per se wasn’t a problem as long as they were healthy foods.

STEVEN BARTLETT: Okay, because there’s been a long, I guess, raging debate about how many meals you should have a day. Some people just eat one meal a day. Some people probably five or six meals a day. And you’re saying it doesn’t necessarily matter as long as what you’re eating is healthy.

DR SARAH BERRY: Yeah, I mean, I will always, as a cautious scientist, caveat it within reason. But our research showed people having six eating events a day, i.e. six different occasions of eating food or three eating events, as long as they were eating or snacking on healthy foods, it did not impact their health outcomes.

STEVEN BERTLETT: And this is, I guess, controlled for extreme cases where someone’s maybe eating at 1 a.m. in the morning or 2 a.m. in the morning.

DR SARAH BERRY: Yeah, so we also looked at timing because I think that’s something that we haven’t given enough attention to in nutrition science. And it’s a really exciting new area of research that we’re starting to understand the timing of when we eat is really important. And what we found was, interestingly, 30% of people were snacking after nine at night.

STEVEN BARTLETT: I feel attacked.

DR SARAH BERRY: And we found that if you snack late at night… And this is in line with other published research from both tightly controlled clinical trials. We found that if you snack late at night, that that was associated with unfavorable health outcomes. So worse adiposity, so worse kind of fat around your belly, for example, higher levels of inflammation, worse levels of blood lipids, so cholesterol, that sort of thing. And we found that this was even if you were snacking on healthy snacks.

STEVEN BARTLETT: Really?

DR SARAH BERRY: And this isn’t especially surprising because there’s this whole new area in nutrition called chrononutrition, which is all about the timing of eating. And we now are really starting to understand that every cell in our body has its little body clock, has a clock. Every cell has a clock. And that clock is shaped by when we eat as well as the light day cycle. And if we’re eating out of sync with those clocks, those millions and trillions of clocks in our body, we know that we process the food slightly differently, we metabolize it slightly differently, and it may have a different impact on our health. And that’s what our research shows as well.

The Impact of Late-Night Eating

STEVEN BARTLETT: So eating after nine o’clock isn’t great for your health. Just to double down on that, I have had a longstanding hypothesis that when I eat later at night, it is basically increasing my belly fat. Now, I don’t have any science to support this. And also, the way that I feel when I wake up is radically different if I’ve eaten close to my sleep time.

So I have this weird hypothesis that I’m basically putting food into the machine and then I’m like turning the machine off while it’s processing. So it’s kind of like not processed it properly.

DR SARAH BERRY: Yeah, I mean, that’s kind of a simple term of what’s sort of happening. Our body needs to rest overnight, just like our mind does. Our cells, our metabolism needs to rest overnight. And if you’re not giving your body, your cells, your metabolism, your gut microbiome, et cetera, that time to rest, things get disturbed a little bit.

And what’s really interesting is you said that you’ll feel different the next day if you eat late at night. There’s some really fascinating research that came out about one or two years ago where they looked at giving exactly the same calories and foods over the day within the same time period, but in one group of individuals having most of the calories earlier and in another group having most of them later in the day.

Now, those that were having them later in the day woke up feeling more hungry, which is kind of like counterintuitive, isn’t it? But it fits in with what you just said. Yet those people who were eating the calories earlier in the day woke up feeling less hungry. And this is why, as well, the evidence shows early time-restricted eating, so time-restricted eating where you’re eating within a particular time window, those people who are practicing earlier in the day tend to do better in terms of the health outcomes, whether it’s weight, inflammation, cholesterol, than those practicing later time-restricted eating when they have their last eating event later in the day.

And that’s because they’re eating in time with their body clocks, with these millions and billions of little cell clocks.

The Effect of Sleep Disruption on Hunger

STEVEN BARTLETT: I had a weird observation, which is sometimes quite rare these days. I have to wake up super early to get on a flight, and it means that I’m disrupting my sleep, maybe getting up at 4 or 5 in the morning. And for some bizarre reason, if I wake up at, say, 4 in the morning to go and get a flight, I am starving.

But if I woke up at 9 that same day, I would probably not get hungry until about 2 p.m. I’ve never managed to really figure out why disrupting my sleep causes me to be ridiculously hungry, whereas typically I don’t, honestly, eat breakfast. I typically eat about midday or 2 p.m.

DR SARAH BERRY: So I think there’s probably a lot going on there. It’s getting a little bit outside my expertise, but I can certainly comment from work that we’ve done and that I’m familiar with. So what we know is that sleep duration, sleep efficiency, what we also call sleep midpoint, so the midpoint at which you sleep, impacts your hunger levels.

We know that your hunger and your fullness hormones change as you sleep. So we know that short sleepers, people who are getting up too early, so when you’re getting up for your flight, then your hunger and fullness hormones might be perturbed. We know that short sleepers, or if you’ve had a poor night’s sleep, you tend to wake up more hungry than if you’ve had a good night’s sleep. This isn’t from my own research. I always have to caveat that, but this is what some of the research shows.

But also, if you’ve had a poor night’s sleep, you reach for less healthy food. There’s a study that was conducted at King’s College London by my colleagues called the Slumber Study. This really nicely illustrates how just changing how much you sleep can change your dietary choices.

In the Slumber Study, they asked people who were short sleepers to practice sleep hygiene. They gave them no dietary advice. They just said, practice good sleep hygiene, i.e. no screens late at night, no physical activity, caffeine, alcohol, etc. late at night, darkened room. Then they just monitored lots of different things in these individuals. What they found was that those who were able to extend their sleep actually made healthier choices, such that they reduced, without being told to, their intake of free sugar by about 10 grams.

STEVEN BARTLETT: Oh, really? Without being given any advice. They slept better, they ate less sugar.

DR SARAH BERRY: They made the decision to eat less sugar.

STEVEN BARTLETT: Yes, without being told to. That correlates. It’s been such a revelation, I think, in my life over the last, I’d say, two to three years, is realizing the downstream impact of sleep and a bad night’s sleep. Because it was one of the things, I think, growing up, especially as an entrepreneur, when you’re consuming a lot of hustle-preneur culture, and it’s all like sacrifice to sleep, work seven days, that you assume is take it or leave it.

You assume it’s often the first thing you think that you can sacrifice in the pursuit of productivity.

DR SARAH BERRY: Sleep.

STEVEN BARTLETT: Yes. This is what I thought growing up.

DR SARAH BERRY: I think all 20 to 30-year-olds think that. Do you not think?

STEVEN BARTLETT: Yes. Anyone that has, I think, probably an involuntary amount of, I say involuntary, but I mean just because of the decisions they’ve made, amount of professional pressure or shift workers or even parents, I guess.

They probably see sleep as secondary to some other kind of priority in their life. And when I shifted that and I made adjustments to my calendar and my schedule to try and prioritize sleep, the downstream impact of it has been profound in a way that I could never measure or articulate fully, but just everything seems to be better. So like my relationships with my partner, my ability to think straight, my motivation to go to the gym that day, the work that I do, everything. So there’s been this big sort of radical adjustment where I now see sleep as actually the starting point for all these other choices that I make, good or bad.

And that’s kind of what your work is highlighting.

The Four Pillars of Health

DR SARAH BERRY: Yeah, I think it’s that we have to think of these four pillars together of health. We can’t look at diet on its own. We can’t look at sleep on its own. We can’t look at stress on its own. We can’t look at physical activity on its own. So if we want to improve health, I think we must be looking at our sleep habits, which we can to a certain extent control. Not always. I know some people have to work shifts. Some people don’t have a choice. They’re woken up by their kids, et cetera. We need to look at our stress.

I know that’s one of the hardest things to change. We need to look at our physical activity and our diet, and they are all so interconnected. And the PREDICT studies that were done at ZOE, found that sleep affected metabolic responses as much as the macronutrient content of the meal.

STEVEN BARTLETT: What is that saying?

DR SARAH BERRY: So this is some research that we published where we looked at people when they’d had a good night’s sleep, and we looked at people when they’d had a bad night’s sleep. And we looked at their post-meal, post-prandial glucose response. So that basically means after having your breakfast, that’s got some carbohydrates in it, how much does your blood glucose increase? We call this the post-prandial glucose response, because post-prandial is Greek for post-meal, and so it’s a term we use a lot in the science.

And we looked at individuals’ post-meal glucose response when they’d had a good night’s sleep and when they’d had a bad night’s sleep. And what we found is within the same individual’s post-meal glucose response, their post-meal glucose response after breakfast was a lot higher than if they’d had a good night’s sleep. So what this shows, I think, quite nicely, if we think back to what you said about how you wake up more hungry when you’ve not had enough sleep, we know that people make poorer dietary choices, for example, from the slumber study, and then we know that the metabolic responses to those are worse. It just shows how you’re kind of creating this perfect storm and how you can’t think of it in isolation.

Because firstly, you’re waking up and you’re like, bloody hell, I’m hungry. Secondly, it’s like, I’m not having that healthy breakfast. I want that pain au chocolat or whatever that’s giving you that quick fix. And then you have it and you’re going to have this massive blood sugar peak compared to if you’d had a good night’s sleep and made a healthy choice, were less hungry, et cetera, et cetera.

So it’s like creating this perfect storm and it’s all started with your sleep. And that’s why I don’t think we can look at things in isolation, which is how I have spent the previous 20 years of my research looking at things in isolation. But that’s because I’ve not had the luxury of being able to collect the kind of data that we’re now collecting.

Parenthood and Sleep Deprivation

STEVEN BARTLETT: I get a lot of messages from parents. So because I’m not one yet, I don’t fully understand what it is to be a parent and the demands of parenthood. So I’m going to defer to you on this. My children never slept.

DR SARAH BERRY: They never slept?

STEVEN BARTLETT: They did, obviously, but oh, my Lord. How did you survive that as a parent? Was there any strategies or tactics you put in place to defend against exactly what you just described, the downstream consequences of sleep deprivation?

DR SARAH BERRY: No, because the first four years of my children’s lives, I lost my father when my daughter, a few weeks after my daughter was born. My sister and I became full-time carers for my mother, who lived around the corner. I took a career break, looked after my mum with my sister, had two young children. They weren’t sleeping. I had to show up. I had to show up to help my sister look after my mum. It was about survival. I didn’t think about what I ate, when I ate. That was irrelevant.

It was about survival, to be there for my mum, to be there for my kids. And whether it was because the sleep deprivation was also so bad that it was just like driving bad choices, I don’t know. But there’s points in time in anyone’s life that we go through that are about survival, aren’t there? And I think everything goes out of the window.

And I’m not saying it should, but I think that when you’re in the depths of, whether it’s sleep deprivation because your children keeping you awake or what I was going through, my mother had a degenerative neurological condition, and seeing someone daily deteriorate like that, what you’re doing physical activity-wise, well, I didn’t have time to do that. What you’re eating quite often doesn’t become a priority. Now, it’s probably a time it should be even more of a priority because we know that what you eat impacts your mental health. There’s great research now showing how important it is.

But when you’re in that fog of whether it’s that you’re depressed or you’re dealing with trauma or whatever, I think food is one of the last things that you think about making a priority. And I think it’s okay.

Mental Health and Food Choices

STEVEN BARTLETT: When we talk about the health situation in the US and the UK with obesity on the rise and things like that, people are now pointing at things like Ozempic as the cure for that. But when you speak about the role there that stress and our lifestyles are having on us, and I was thinking about some of the stats that have emerged around anxiety in young people and depression rates globally, maybe there’s something else that we should be thinking about, which is the mental health mindfulness piece of how that overlays with food choices.

Because even the ultra-processed unhealthy foods that are being attacked a lot these days, to some degree they are a consequence also of demand. They wouldn’t be making these things if people didn’t want them and didn’t buy them. So maybe if we focused more on some of the mindfulness, mental health challenges we have in society, people would have more of a greater ability to make better choices for themselves as well. Because I certainly know in my life that if I’m highly stressed or if things are difficult, then my ability to make better food choices is significantly impaired.

DR SARAH BERRY: Yeah, absolutely. Again, this is what the research shows, the sleep, the stress. It impacts your ability to make choices about lots of things, but equally your food choices. What you’re talking about I think is so complex. It’s where’s the responsibility for the government, where’s the responsibility for the food industry, where’s the responsibility for us as individuals, where’s the responsibility for schools, for example, or for us as parents educating our children. We need to take into account all of those different areas in order to improve the foods that we’re eating.

There is a problem that these three dishes, so the chocolate, the biscuits, the crisps, they are more tasty or rather our taste buds, our brains are tricking us into thinking they’re more palatable. And that’s a problem. Do we say to our children, you can never, ever have them? Now, I’ve certainly never taken that approach. It’s all about balance and enabling people to make the choices that they make. But I recognise if I’m sitting there in the evening, I’m a bit stressed, I’ve got a work deadline, I don’t want to eat nuts.

Balancing Nutrition and Enjoyment

DR SARAH BERRY: I want to eat those biscuits or those crisps and I want a glass of wine with it. I know that’s not the right decision. I know it’s 10 o’clock at night. But in the moment, that’s the choice I probably will make.

STEVEN BARTLETT: Do you get frustrated with yourself because you know more about nutrition than most people on planet Earth, yet you still find yourself making at times suboptimal nutritional choices?

DR SARAH BERRY: No, I don’t. Because I think that it’s really quite simple when we think about the food that we eat. I think we’re making it so complicated. And I think that, you know what, if we eat a good amount of fruits, vegetables, pulses, if we try not to eat too much heavily processed foods, if we try and get a bit of diversity in our diet, we’re doing okay. So what if I go and have a bar of chocolate? As long as I’m not doing it all day, every day.

And I think this kind of health optimisation around diet I think is taking away the pleasure of food. And I often say if a food is too healthy to be enjoyed, it’s just not healthy at all. Food is there to bring us joy, it’s to bring us pleasure, it’s part of our emotions, it’s part of our culture, it’s part of our social connections. And I worry that now there’s a certain proportion of society so hyper-focused on that 1% gain in terms of the food that they’re eating that they forget all of that pleasure.

So I think I have quite a balanced approach because I know that ultimately if you get the foundations right, the rest will follow. But that makes up 95% of what makes a food or a diet, and that’s how we need to think about what we eat healthy.

Views on Different Diets

STEVEN BARTLETT: What do you think of diets? Because there’s so many bloody diets, isn’t there?

DR SARAH BERRY: I think that there’s so much neutrobolics out there.

STEVEN BARTLETT: Neutrobolics.

DR SARAH BERRY: There is so much misinformation out there. What you see on social media versus what the evidence shows is like night and day. I mean, seriously. And so when I think about diets, my view on diets, I mean, there are some that there’s some good evidence. Eat 30 plants a week, yeah, that’s great. Go on a low-calorie diet to lose weight, great, but how are you going to maintain that weight? That’s a whole other question. Great for losing, not for maintenance.

Then you’ve got the alkaline diet. I mean, I don’t understand that. Eat alkaline foods, but your stomach is acidic, so I’ve got no idea how that works. The blood type diet, I don’t actually know what half of these diets do because I do not understand the physiological theory behind them.

And so, you know what, though, Stephen, I think if it works for you as an individual, fine, do it. But if it works for you at the expense of the pleasure of food, at the expense of enjoying life to the fullest, that’s what I think’s a shame.

Time-Restricted Eating

DR SARAH BERRY: Like time-restricted eating, I think there’s great evidence around time-restricted eating. Now, much of it comes from very tightly metabolically controlled studies that are done in clinic where people eat within a five- or six-hour window. So they have their first meal at 10, their last meal at 4 in the evening. Reduces inflammation, reduces body weight, improves blood cholesterol, et cetera, et cetera, et cetera. I don’t want to only eat six hours a day. I want to have dinner with my family. I want to have dinner with my friends. I want to go to the pub in the evening, not every evening. I want to live life.

So what can we do that takes that principle of that diet but we still benefit from it? And this is what’s great, again, about the research that we’re doing at ZOE. We’ve done this study called the Big F Study, the Big Intermission Fasting Study, where 150,000 people sign up. And we said, look, we want to see if what we find in tightly controlled clinical studies plays out in the real world because we always have to think, how does all of this evidence play out in the real world? Does it matter?

And we said, just limit your eating window for the time from your first to your last meal to 10 hours. So that means if you’re having your first meal at 10, in the morning, you’re having your last meal at 8 in the evening.

STEVEN BARTLETT: That’s correct, isn’t it?

DR SARAH BERRY: Sure. My pain and the poor brain cannot do math.

STEVEN BARTLETT: That’s quite doable for most people. I can have my breakfast at 10. I can finish my last meal at 8. I mean, yeah, I do like munching on my chocolate late at night. I could probably still live a happy enough life doing that.

DR SARAH BERRY: And we found people could do it. We found as well that people who practiced it within two weeks, they felt better. They had better energy, better mood. They were feeling a lot better. They also lost weight. Many people wanted to do this because they wanted to lose weight. And we actually see from evidence that people practicing time-restricted eating, even if they’re told not to change their calorie intake, just by limiting their eating window on average, reduce their energy intake by about 300 calories on average.

STEVEN BARTLETT: There’s been a big debate around this conversation around fasting and calorie restriction. And some people say that it’s basically the same thing. And you’ve kind of proven that to some degree.

DR SARAH BERRY: So we know that in most instances, if you practice time-restricted eating, you unintentionally reduce your energy intake. And the data shows that on average, from the studies that are published, it’s about 300 calories. Obviously, it depends on the situation. The reduction in body weight also we know is dependent on the eating window. The smaller the eating window, the greater the reduction in body weight.

But there have been some studies that actually control the amount of calories that people eat. Some people having it in a bigger eating window, some in a smaller eating window. And what these studies have shown is that if you have the same amount of calories, but you change the period in time in which you’re eating your food, there is an additional benefit on metabolic health. There is a benefit in terms of blood lipids, in terms of inflammation.

STEVEN BARTLETT: Independent of calories.

DR SARAH BERRY: Okay, so time-restricted eating has some benefit independent of calories consumption.

STEVEN BARTLETT: Yes, but the bulk of the benefit is due to a reduction in calories.

DR SARAH BERRY: So there’s some benefit independent of calorie restriction, but the bulk of the benefit that we see is due to a subconscious or unintentional reduction in calories. And I think this is when we’re thinking about diets. I think we need to think about how easy is it to implement? Is there any evidence behind it? And 99% there isn’t. For the ones that there is evidence, like time-restricted eating, can we do it in a way that still enables us to live our life that’s sustainable?

Consistency in Eating Patterns

DR SARAH BERRY: And the sustainable point I think is really important because there’s now some new evidence emerging around consistency and the importance of consistent eating patterns. And I think this is fascinating. So there’s research showing that if one day you’re having three meals and the next day you’re having nine meals, and the next day you’re having six meals, and the next day you’re having four meals, that troubles your body. It’s like, whoa, hold on, I’m used to having four eating events a day.

And this is important to bear in mind when we think about snacking. If you’re typically a snacker, then fine, carry on snacking as long as it’s on healthy food and as long as you have your last snack before nine at night. If you’re not a snacker, having me just vouch for the great benefits of snacking, don’t start snacking because you don’t want to be inconsistent. And this new evidence emerging around the consistency of eating, and there’s some research done actually quite some time ago that started this idea, I think is really fascinating. So try and have a consistent eating pattern.

Same applies to sleep. Try and go to bed at the same time, get up at the same time. We’ve done some work around social jet lag. I don’t know if you’ve heard of that term.

STEVEN BARTLETT: I think I’ve heard of it. What does it mean?

DR SARAH BERRY: So social jet lag is where you have an inconsistent sleeping pattern throughout the week. So for example, for many, maybe 20-year-olds or students, they might go to bed at a sensible time in the week and go partying and crazy at the weekend. Or for someone like myself, I go to bed late at night because I’m late night working, parenting, et cetera, and then at the weekend I catch up.

So if you have more than about a one and a half hour increase or decrease in sleep between your work days or weekend days, et cetera, that’s called social jet lag. So it’s a bit like jet lag going from one country to the other. And what we know is, and we’ve published on this from our own very particular research, people who experience social jet lag, so have this inconsistent sleeping pattern, make poorer dietary choices. They have more inflammation. They have a different gut microbiome composition.

Now it might be because of the dietary choices, but again, it just plays into this whole idea that we’re talking about that we can’t just think about the food in isolation. We need to think about how we’re eating, our lifestyle, et cetera.

Debunking Nutrition Myths: Seed Oils

STEVEN BARTLETT: What else is on your Nutribolics list? What things spring to mind that a lot of people believe? I mean, there’s a big debate raging at the moment about seed oils because we had an incoming American, I guess he’s a politician, RFK Jr. say recently, seed oils are one of the most unhealthy ingredients that we have in foods.

And the reason they’re in foods is because they’re heavily subsidized. They’re very cheap, or they are associated with all kinds of very serious illnesses, including body-wide inflammation, which affects all of our health. It’s one of the worst things you can eat, and it’s almost impossible to avoid if you eat any processed food.

DR SARAH BERRY: Sorry, I’m having to laugh. This is like Nutribolics beyond Nutribolics.

STEVEN BARTLETT: That’s basically it. He said if you eat any processed foods, you’re going to be eating seed oils. And he advocates for replacing seed oils with beef tallow, which in the UK is referred to as dripping, which is pure beef fat and is a saturated fat. And he’s actually selling t-shirts, RFK Jr. at the moment, that say make frying oil tallow again.

So what is this weird debate that I’ve seen raging on on my Instagram about seed oils? I’ve managed to avoid it. I’ve just not paid attention to it. But I see the word seed oils all of a sudden everywhere.

DR SARAH BERRY: Okay, so seed oils, I think, is at the top of the Nutribolics list. It blows my mind what you’ve just read me. It seriously blows my mind. I’ve done lots of research on seed oils, so I can talk from my own research, as well as all the evidence bases out there. There is absolutely no evidence that is credible evidence when interpreted in the correct way to show seed oils are harmful.

STEVEN BARTLETT: What is a seed oil?

DR SARAH BERRY: So a seed oil is an oil from a seed. So the most common seed oils in the UK is rapeseed oil, which is also known as canola oil in the US and many other countries, followed by sunflower oil. The most common seed oils in the US are soybean oil, followed by rapeseed or canola oil, followed by sunflower seed oil.

There’s about three or four arguments that people use to say that seed oils are bad for us. If you go on social media, this is a perfect example of night and day between scientific evidence and what’s on social media. If you go on social media, seed oils are toxic, seed oils are going to give you Alzheimer’s, seed oils are going to give you cancer, seed oils are going to kill you. You look at the evidence, it’s totally the reverse.

Now, you can have sensible, boring scientists like me say, seed oils are really good for you. You could put that as one of your assets or whatever you call it, or adverts for this. So we could say, seed oils are really good for you, Stephen. Or I could tell you, seed oils are toxic, they’re going to kill you. Everyone’s trying to kill us with seed oils.

STEVEN BARTLETT: What’s going to get more clicks?

DR SARAH BERRY: Probably the toxic seed oil.

STEVEN BARTLETT: Exactly.

DR SARAH BERRY: And so the sensible science, there’s no silver bullet, there’s no crazy inflammatory argument. The sensible science isn’t going to get the clicks. So unfortunately, the voices of reason, and often it comes from boring academics like myself, not saying other academics are boring, but sensible academics like myself that give the balance, we don’t get a voice. We’re not being heard, which is one of the reasons that I wanted to come on this show because of the misinformation. We have to get the voice of reason out there. We have to get the voice of reason. So things like that, to do with seed oils, are not what’s dominating the headlines.

So what people say in terms of seed oils is, firstly, our intake of seed oils has increased a hundredfold the last 20, 30, 40, 50 years. And with that increase in seed oil intake, so has cancer increase, so has cardiovascular disease increase, so has obesity increase, so has Alzheimer’s etc etc. So it must be to do with the seed oils.

Well what else has changed in that 50 years? We’re more sedentary, we eat loads of these other, these heavily processed foods that have got all of these other ingredients in, you know the sugar, the this, the that, so much else has changed. You know you can’t put it all down to the fact that at that point in time seed oils were also changing.

Debunking Myths About Seed Oils

DR SARAH BERRY: We also know that about 60% of the seed oil that we eat is actually in these heavily processed unhealthy foods. So it’s the first argument they say and you see these beautiful figures that they put out where you see on one axis the intake of seed oil, you see on the other axis, you know over time you’ll see for example like rates of cancer and you see rates of cancer or rates of cardiovascular disease going up linearly with the intake of seed oil. But we have to think what else has changed in that time.

The other arguments that they use are theoretical arguments based on biochemical pathways and I spend an hour teaching this to undergraduates and I’m not going to bore you with that biochemical but they talk about the ratio of a particular fatty acid which is omega-6 which is found in high levels in seed oils and omega-3 which is another fatty acid and they talk about how having lots of seed oils changes this ratio, makes this pro-inflammatory state because it increases a particular downstream chemicals etc etc.

What we know from kind of theoretical biochemical pathways and enzymes etc doesn’t actually play out in humans. We’re so clever, we have all of these mechanisms in place to control inflammation, to control oxygen stress, to control downstream impacts of foods and so this argument that is also used to say that omega-6 fatty acids, so the main fat that’s found in many of these seed oils is pro-inflammatory, is not supported by any evidence.

It’s not supported by tightly controlled clinical trials, if anything it’s shown to be anti-inflammatory that levels of inflammatory circulating molecules actually reduce and yet they use this kind of theoretical argument or what they’ve seen in a petri dish for example or in a test tube.

STEVEN BARTLETT: So where is this narrative come from? Where did it originate from that seed oils were toxic? Was it just one of those things that just snowballed?

DR SARAH BERRY: I think it’s one of those things that snowballed and I think it does fit in with the whole argument that people are using against processed food. It does fit in with other narratives that are going on.

I think some people can be very clever in cherry-picking research. So there’s a study called the Sydney Heart Study and in this study, this was done in the 70s, and this is a study that’s used often to advocate for the toxic effects of seed oils. And in this study, males that had a heart event or a heart attack of sorts were randomly allocated to either increase their omega-6, so this particular type of fatty acid that is in seed oils in their diet by having lots of seed oil or they were asked to just follow their normal diet which is quite high in saturated fat. And what they found is those that increased their seed oil intake went on to have worse health outcomes.

Now the problem with that is that in those days the majority of seed oils underwent an industrial process called partial hydrogenation and partial hydrogenation produces a very harmful fat called trans fats. You might have heard of trans fats.

STEVEN BARTLETT: I’ve heard the word, yeah.

DR SARAH BERRY: And so they were eating the seed oil in the form of a margarine or fat spread that had undergone partial hydrogenation and therefore was full of trans fats. Trans fats increase cholesterol, trans fats increase inflammation, trans fats are bad for us, that’s why they are not in our food supply anymore. And so of course that seed oil was going to cause worse health outcomes but it’s not how seed oil is consumed now. And so it’s that clever cherry-picking of evidence that often supports a lot of the neutrobolics that’s out there.

STEVEN BARTLETT: Yeah and you know people, you know, with all these studies out there and with some studies having less rigor and studies that aren’t, don’t have sort of the randomized control element or what’s the other term for a study where they do, they look at like 50 studies at once?

DR SARAH BERRY: So they’re meta-analysis so we do randomized control trials. So these will be trials where there’s always a control arm, we’ll randomly allocate some people to an intervention like seed oils and some people to a control, could be saturated fat, could be beef tallow, that’s been done. And then we look at different health outcomes, we follow them over a period of time or it could be that I ask you for a month to have seed oils and then next month have beef tallow for example and then we’ll look at different health outcomes, compare how you responded to one versus the other.

And then what we do as scientists is if there’s enough of these clinical trials, these randomized control trials, we put them all together into what’s called a meta-analysis and we look what does the meta-analysis show.

So for example for seed oils there’s meta-analysis for example of about 42 randomized control trials where they compare seed oils to other fats showing consistently that there is no harmful benefit, that actually there’s a reduction in cardiovascular disease because the particular fat that’s in seed oil has a really potent cholesterol lowering effect, it’s actually beneficial for our health.

Yet beef tallow is full of saturated fat, it’s full of palmitic acid which is a particular type of saturated fat that we know is bad for us. There have been studies and these studies were done many years ago when beef tallow was actually used, comparing seed oils with beef tallow. Seed oils always came out better, seed oils always reduced cholesterol compared to beef tallow, reduced inflammation etc, reduced cardiovascular risk factors.

STEVEN BARTLETT: You’re very passionate about this.

The Challenges of Nutrition Research

DR SARAH BERRY: I am because I’ve researched, as a research active scientist where I’ve run randomized control trials and I tell you what, you sweat blood and tears, I love my research but it’s blimmin’ hard work doing a clinical trial, you know getting ethical approval, recruiting people, changing people’s diet. Running dietary studies is really hard because it’s not a case of giving them a pill. If I’m going to give you seed oil, I think well how am I going to do that?

Instead of what am I taking out of your diet to give you that, how am I going to make sure the rest of your diet is controlled? So once you’ve run studies yourself and you’ve sweated that blood and tears and then you see this neutrobolics, this misinformation out there, it’s really bloody frustrating.

STEVEN BARTLETT: But it’s a good thing that people like yourself are leaning into the mediums now of like podcasting because it’s worth saying that as it relates to the sort of transfer of information, it’s typically people who have either a platform or who are great public speakers or great sales people that are ultimately going to like resonate the most, reach the furthest with their information irrespective of whether that information is credible. So it’s good to see more and more people that are in the research now sort of stepping away from the research laboratory and coming into environments where they can provide counteracting information.

And as someone that’s on my own journey to figure to sort of weave through all of this information to find out what’s right for me, it’s difficult. And for a lot of people it’s super difficult. I mean the way that I kind of my own framework for this is I listen to things and then I don’t necessarily trust one source to be true. But I almost like weight the authority experience and the rigor behind how they’ve arrived at that information.

And then I guess I perform my own meta-analysis across lots of different people that I speak to and guests and information that I get to find the sweet spots where the sweet spot for me is many people have said it that I think have a lot of rigor and authority and experience in that subject matter. So then I accept it to be true. Whereas I’m not going to go on Instagram and see a real pop-up and it says that I don’t know putting sugar in your eyeballs is good and I’m not going to crack on with it just because the person’s got charisma. And I think in the world we live in where there is now this decentralization of information which has its upsides and its downsides, we all need to have our own decision framework to decide what is true.

DR SARAH BERRY: But I think yours is more rigorous than most. Many people get their information from one source, many people trust one source and you’re right that as academics we’re rarely given a platform. And this is what I valued most actually about what I’ve done at ZOE, well being able to do the kind of trials that we’re doing, but being able to have a platform not just for me but for us to invite other credible scientists onto the ZOE podcast or for me to come onto this kind of podcast.

We’re not trained as academics how to communicate, we’re trained how to run good studies in my case, run clinical trials, interpret the evidence, evaluate the evidence, critique the evidence. And I’m self-taught to present the evidence to other academics but we’re not taught to communicate it to the general public. So for me it’s been a journey working at ZOE of trying to communicate really complex stuff. I would have loved to have spent an hour telling you about the biochemical pathway of why seed oils don’t impact inflammation. But I know that really you’re not interested, the listeners aren’t interested, but you know I’m hoping that by informing them that I’ve done these studies and that these are the results there’s trust that actually what we found is true.

But we’re the smallest voice out there, the research active scientists, partly because of time. I’m still running trials, running different interventions, but also I think many of the big platforms aren’t giving us the opportunity necessarily because we haven’t got the most exciting things to say because at the end of the day we’ll present the evidence, we’ll present it with caveats, we’ll present it with caution. And you know I will always say on, as I work with students I’m teaching, what I’m telling you now is based on what the evidence shows now. In 10 years time I might be totally wrong.

All of these trials showing seed oils are fine. I might be wrong in 10 years time. I mean I doubt it, I doubt it because there’s enough research. But as scientists that’s something else you know we always caveat with.

And I think sometimes that’s difficult for the general public maybe, I mean I might be doing a disservice, I don’t know, that you have the non-active influences, science influences, I don’t know what you call they speak with such certainty. Now I will if it’s my study, so I’ll talk with certainty over the seed oil study because I’ve done them, I’ve been there in the lab analyzing it. Or I’ll speak with certainty over snacking data because I’ve you know sweated blood and tears over you know running the stats etc. But I won’t talk with certainty about anything else that I haven’t done myself and yet you have other people talk with such certainty and I think that’s what instills confidence in maybe listeners and that’s why they get more viewers.

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Dairy and Nutrition

STEVEN BARTLETT: There’s a lot of neutrophilics around dairy right?

DR SARAH BERRY: Yep.

STEVEN BARTLETT: I think the prevailing neutrophilics is that dairy is bad for you?

DR SARAH BERRY: Yep so there’s not lots of neutrophilics around dairy and it’s related to the neutrophilics also around saturated fat. So as a whole we know saturated fat is bad for us. Dairy contributes to most of the saturated fat intake in the UK so therefore we could say all dairy is bad for us. But no, dairy is a diverse food group. You’ve got cheese, you’ve got yogurt, you’ve got butter, you’ve got milk and how they impact our health is vastly different depending on whether it’s a liquid, a solid, it’s fermented, it’s non-fermented etc etc. And grouping them all together is as ridiculous as grouping all these snacks together in terms of their health effects.

And what we now know is that some dairy is actually good for us. So some dairy like cheese, like yogurt, and I don’t mean this really kind of heavily sweetened sugary yogurt, I mean like your greek yogurt, your kaffirs, those sorts of things, your plain yogurts, they’ve undergone a process called fermentation and that changes the food matrix.

So again we’re coming back to that whole importance of the structure of the food and by changing the food matrix changes how our body handles it, the health effect of that cheese. We don’t fully understand how, there’s some great research being undertaken at Reading University really diving into this.

Dairy and Cholesterol

DR SARAH BERRY: But what we know is if you have cheese within reason, if you have yogurt within reason, it does not increase your cholesterol despite being high in saturated fat. Now have precaution that I’m not saying people should go and have you know 300 grams of cheese every day but within normal kind of intakes of a few portions a day it does not increase people’s cholesterol having cheese or having a good yogurt. Butter on the other hand we do know does increase your cholesterol. Now if you’re having it at a kind of level that you would maybe just putting on a bit of toast I wouldn’t worry so much but we do know that if you were to compare cheese versus butter which has almost the same fat composition and this has been shown in randomized controlled trials, the butter will increase your cholesterol but the cheese will not.

Nuts and Weight Gain

And nuts, a lot of people say that nuts cause weight gain. No the evidence does not support that. So we know that people who consume nuts based on the totality of the evidence do not gain weight. We know this from epidemiological data i.e. people who consume more nuts tend to quite often have a lower BMI. Now that could be confounded by the fact that nut consumers and only about 10% in the UK and even less about 7% in the US even consume nuts. Nut consumers tend to have a healthier overall diet so there is that confounding but clinical trials show that if you add nuts to your diet, ours included, you do not gain weight.

Now that might be partly because of the mechanisms that we’ve talked about to do with the food matrix that 20 to 30 percent of the calories are being excreted. So the back-of-pack labeling shows that per portion of nut is 170 calories but actually on average you only absorb 130 calories so lots of it’s coming out. It might be because you know they’re feeding the microbiome that’s helping you know reduce adiposity. It’s also nuts are satiating so they make you feel more full. They also blunt your blood sugar response. They have so many other benefits that counterbalance any potential for weight gain.

Understanding Cholesterol

STEVEN BARTLETT: And is there anything else on the NutriBolics list that is worth highlighting?

DR SARAH BERRY: I would say that I think there’s still lots of confusion around saturated fat and around cholesterol. So cholesterol, I went and did a blood test and the doctor said to me that one of my cholesterol was a little bit on the higher side.

STEVEN BARTLETT: This was last year so and it was the — is it the HDL cholesterol? I don’t know. The way that I experienced it was there’s this good cholesterol and this bad cholesterol and like my bad one was like a little bit you know behave like it’s getting a little bit into the region where he might have more of a stern talk with me. That was last year. I think I’ve done better this year but what is cholesterol and my simplified explanation of it is that is that flawed in some way? A good bad?

DR SARAH BERRY: No it’s always a little bit more nuanced a little bit more complex but there are two ways that we can look at cholesterol. We can look at cholesterol in terms of the cholesterol that we eat right and that’s where I think there’s a lot of misinformation and we can look at cholesterol in terms of the cholesterol that our body produces.

So our liver is constantly churning out cholesterol. When the liver churns out cholesterol it packages cholesterol into two different kinds of packages or two different types of parcels and the labeling so to say on these parcels determines the health effects of that cholesterol. So you’ve got your HDL cholesterol which we call our good cholesterol. You’ve got your LDL cholesterol which we call your bad cholesterol.

Because L is bad, H is good. They’re actually the same in terms of the cholesterol but it’s the label that’s on the parcel the label in terms of which is directing where they go which is different. So in really simple terms LDL is directed, posted to your peripheral tissues to your blood vessels where it can be taken up and in the right environment where there’s inflammation, stress etc can result in atherosclerosis which is that kind of furring of the arteries which over time can build up and can lead to a heart attack etc etc. HDL in very simple terms has a label on it that actually enables the reverse cholesterol transport so it actually almost kind of cleans up some of the cholesterol.

This is kind of in very simple terms so if any lipidologists are listening they might be a bit frustrated but in very simple terms it kind of brings it back to the liver for disposal. So that’s why it’s considered good. What we know is that the amount of LDL cholesterol that’s circulating is really important in terms of our cardiovascular disease risk. There are some cholesterol deniers and I know you’ve had on your show a cholesterol denier. I don’t believe in the evidence he presents. I think that the totality of the evidence is very very clear that as your LDL cholesterol increases your risk of cardiovascular disease, your risk of all-cause mortality increases.

Where there is misinformation is around dietary cholesterol, that there was this perception years ago that if you have foods high in dietary cholesterol like eggs that it will increase your circulating cholesterol and therefore increase your risk of heart disease and therefore there was a limit years ago put on how many eggs we should eat, how much cholesterol we should consume. We now know within certain limits, so within the limits that we typically eat our food containing cholesterol, that dietary cholesterol does not impact our circulating cholesterol.

Obviously at extremes it does but if you’re having one to two eggs a day that’s an intake of cholesterol that’s not going to negatively for most people impact your circulating levels of this LDL bad cholesterol. If you’re having 10 eggs a day then I would be worried.

STEVEN BARTLETT: Okay, okay. But yeah cholesterol is another area of neutropolics and then you know on this whole area of cholesterol, heart disease, I think a really frustrating area of neutropolics is saturated fat.

Dietary Cholesterol vs. Circulating Cholesterol

STEVEN BARTLETT: So we’ll talk about saturated fats just so I’m super clear on the cholesterol point. What foods have really high levels of LDL circulating cholesterol in them?

DR SARAH BERRY: Okay, so you’ve got dietary cholesterol which is just the cholesterol that’s in the food and that has very little impact on circulating cholesterol. Then you have cholesterol that the liver produces and the liver produces that from scratch and it’s how diet impacts the liver production that determines how diet impacts our circulating cholesterol.

So saturated fat increases the production of cholesterol by our liver and reduces the removal of cholesterol by our liver. Highly refined carbohydrates can also increase the production of cholesterol by our liver. So when we’re thinking about how diet impacts our cholesterol, particularly our LDLs, our bad cholesterol, we don’t need to worry so much about dietary cholesterol, i.e. how much cholesterol is in a food because unless it’s extreme it will have a minimal impact. We need to think about how much saturated fat for example we’re having because that’s one of the main dietary determinants of our cholesterol level.

STEVEN BARTLETT: Okay, and what is a saturated fat versus like a normal fat? Like is that good and bad fats?

DR SARAH BERRY: Yes, good and bad fats. All of the fats that we eat or 98% of the fat that we eat comes in the form of a molecule called triglyceride and a triglyceride has within it three fatty acids and it’s the mix of these fatty acids that determine the health properties of that triglyceride, the melt profile of that triglyceride, etc, etc. and there’s lots of different types of fatty acids. So you’re probably familiar with amino acids which are types of protein and in the way that amino acids are what make up protein, fatty acids are what make up a fat and the quality of that fat and we typically separate them into three main classes, saturated, monounsaturated and polyunsaturated.

STEVEN BARTLETT: You might have heard of those terms?

DR SARAH BERRY: Yeah, loosely, yeah. And saturated fatty acids differ in terms of their biochemistry, I won’t bore you with that, to mono and polyunsaturated fatty acids. They also differ in terms of their melt profiles, so like how hard they are or liquid they are. Most tend to be hard, hence why most hard fats like butter, you know, most animal fats which are hard at room temperature tend to be high in saturated fats. Mono and polyunsaturated fatty acids differ from saturated fatty acids in terms of their biochemistry, in terms of their melt profile, they tend to be liquid. And polyunsaturated fatty acids are a very special type of fatty acid because they’re actually essential for us, our body can’t make them.

And so they’re essential fatty acids and one of those is omega-6, which is the fatty acid found in seed oils, which is what people say is why seed oils are bad for us, which hopefully we’ve debunked there.

Saturated Fat and Cardiovascular Disease

DR SARAH BERRY: And saturated fat as a whole, we know, is linked to increased risk of cardiovascular disease, increased risk of all-cause mortality. But there’s lots of people that say, you know, we’ve got it wrong as nutritional scientists, we don’t know what we’re talking about it, because actually there’s this meta-analysis that showed that actually saturated fat isn’t bad for us. And that’s because when we think about the health effects of food, we have to always think of that instead of what.

So there was some work that was carried out looking at hundreds and hundreds of different clinical trials where they’ve replaced saturated fat in the diet with carbohydrates or trans fats or polyunsaturated fats or monounsaturated fats. And what this research showed is that if you replace saturated fats with whole grain carbohydrates, you have an improvement in health. If you replace saturated fats with poly or monounsaturated fats, you have an improvement in health. If you replace saturated fats with refined carbohydrates, there’s no difference.

So you could take that study and you could say, and this is of hundreds of different studies, and say saturated fats are really bad for us because we know that if you replace them with whole grain or poly or monounsaturated fats, you have a beneficial effect. Or I could take the same analysis and say, oh, saturated fats are fine. Nutritionists have got it all wrong because actually there’s no detrimental effect if you compare it with refined carbohydrates. And this is exactly what happened when this meta-analysis came out about, probably about 15 years ago.

I remember looking at the headlines of two different papers. I won’t say what the papers are, but one, I would say it’s a little bit more evidence-based and one is a good example of clickbait headlines. They had totally different headlines. One said, nutrition scientists have got it all wrong. We’ve been lied to. Saturated fats are fine. The other said, research, again, consistently shows saturated fats are detrimental to our health.

STEVEN BARTLETT: Obviously that one’s right. And they’re talking about the same study?

DR SARAH BERRY: Talking about the same study because it’s there instead of what? And that’s really important when we think about the health effects. The other thing that does complicate things a little bit with saturated fats is there’s lots of different types of saturated fats. We know that the type of saturated fat matters, but we know the food matrix that it’s in matters. And the dairy is a great example. So you have cheese and butter, exactly the same or almost identical fat composition, two entirely different effects on our cholesterol. So it is a little bit more nuanced than saying all saturated fats bad. It depends on the type and the food it’s in.

STEVEN BARTLETT: And what types of food have saturated fats that have a less than healthy food matrix?

DR SARAH BERRY: So I would say the type of saturated fats that we want to avoid are the saturated fats that are found in most animal products except fermented dairy, except cheese, except yogurt. So beef tallow, I would say the evidence consistently shows it’s not favourable for our health. Lard, butter in large amounts.

And then the meat, the fat that’s intrinsic to the meat, take salami, you can see the fat in there. Take steak, for example, cut off the visible bits of the fat. It’s okay in small amounts. I’m not saying we should avoid it totally, but if you have the option of cutting off trimming the fat, then I would.

And then there are some tropical oils that are very high in saturated fat. Palm oil, for example, coconut oil, although the jury’s out on the health effects of coconut oil, but palm oil, for example, is very high in saturated fat. We know it increases our cholesterol.

Five Principles for Eating

STEVEN BARTLETT: If you had to give me some principles for eating based on everything we’ve talked about today, just like, and I had to force you to just give me five principles for eating, what would those five principles be?

DR SARAH BERRY: Five, okay. I would say first and foremost, find food or dietary pattern that you enjoy, that brings you pleasure.

STEVEN BARTLETT: Cookies.

DR SARAH BERRY: Okay, but we are not, these aren’t exclusive to each other, okay.

STEVEN BARTLETT: That’s really important. These are not exclusive.

DR SARAH BERRY: Okay. So a dietary pattern that brings you pleasure. Because food is there to be enjoyed and it will be a sustainable dietary pattern. And because we know that consistency and sustainability is really important in how you eat. Okay. Second, I would say, think about how you eat. Think about how fast you’re eating. Slow down. Chew more.

STEVEN BARTLETT: Chew more.

DR SARAH BERRY: Don’t eat late at night. Try and eat within a 10 or 12 hour eating window.

STEVEN BARTLETT: And just on this chew more point, before we started recording, you were saying that you wouldn’t mind if I chewed some nuts and spat them out so you could look at them. Why does chewing more have an impact again, just so I’m clear?

DR SARAH BERRY: So chewing can impact how you break the food down, obviously. But we also know chewing impacts your hunger and your fullness signals. So there’s some evidence to show if you chew your food 40 times versus 15 times, it can result in a difference in how full that food makes you feel.

STEVEN BARTLETT: Okay.

The Importance of Chewing

STEVEN BARTLETT: So the chewing effect is sending some kind of signal to my brain.

DR SARAH BERRY: Yep. Again, this isn’t an area that I have expertise in, but that’s what the evidence is showing. So as well as your gut sending signals to your brain, receptors on your gut saying whether you’re full, there’s something going on when you’re chewing your food as well. That’s important. And chewing your food also changes the rate, therefore, at which you’re eating. So it changes your eating speed.

STEVEN BARTLETT: Okay. So on that second point, I’ve got slow down, chew more, don’t eat late at night. And eat within a 10 to 12 hour eating window.

DR SARAH BERRY: 10 to 12 hour eating window. Then the third would be go back to basics.

STEVEN BARTLETT: Yep.

DR SARAH BERRY: Have a good amount of fiber, have a good amount of healthy oils. That’s your olive oils and your… Olive oil, there I say it’s seed oils, but olive oil I would say is the king and queen of the oils. And have that balanced plate rather than obsessing over a single food.

STEVEN BARTLETT: Okay. Number four?

DR SARAH BERRY: Don’t think of food in isolation.

STEVEN BARTLETT: Okay.

DR SARAH BERRY: Think about your diet in relation to or alongside your sleep, your stress, your physical activity.

STEVEN BARTLETT: And number five? Can you remind me of what I’ve done?

DR SARAH BERRY: Yes. I’m 48. I’m in the depths of… I’m one of those 90% of people that have brain fog and memory loss.

STEVEN BARTLETT: So number one was food that brings you pleasure, which is sustainable and allows you to be consistent. Number two is really thinking about how you eat. So slowing down, chewing more, not eating late at night, and trying to have a shorter eating window of 10 to 12 hours. Number three was go back to basics, which is high fiber, whole grains, fruits, healthy oils, and overall just a balanced plate. And number four is don’t think of your nutrition in isolation. So think of it in the context of your exercise, your sleep, and all of these other lifestyle factors. And number five?

DR SARAH BERRY: Don’t deny yourself anything.

STEVEN BARTLETT: All right.

DR SARAH BERRY: Think about what you can add in rather than what you take away. Don’t deny yourself anything.

STEVEN BARTLETT: So cookies are still on the menu?

DR SARAH BERRY: Occasionally, yes.

Perimenopause and Nutrition

STEVEN BARTLETT: You mentioned the perimenopause. You said you’re in perimenopause currently. How does that factor into everything we’ve talked about today? And what is the… Because I’ve got this graph here that I’d found about the menopause transition, which talks about how different sort of things are happening inside the body. You’ve probably seen this quite a few times before, which I’ll put on the screen and link below for anybody. But what is the relationship between my diet and my menopause journey? Is there anything to be aware of?

DR SARAH BERRY: There is. I mean, the menopause has a huge impact on how we respond to food. It has a huge impact generally on all of these pillars of health that we’ve talked about. Our sleep, our stress, our physical activity, and diet. And I think it’s something we’re talking about a lot more now. And we should be talking about it a lot more now. You know, 50% of the population at some point are going to go through the menopause.

And it’s a transitional period of great disturbance, great disruption, and of great burden to many women. And we’ve conducted lots of research on the menopause. And what we know is that prior to the menopause, which is basically the point one year after your last menstrual cycle, you have this perimenopausal transition period where your estrogen and other hormones are fluctuating day to day. So it’s like this roller coaster, which I think your graph shows really nicely.

You’ve got this roller coaster of hormones. And so what’s happening is your estrogen isn’t just slowly declining as you reach perimenopause. So that transitional period before your menopause, but you’re on this roller coaster. And it becomes more regulated after the menopause. But you’re still in that point where you’re having less estrogen, so less of the hormone that we know has such wide-reaching effects.

And the reason that the perimenopause transition, as well as post-menopause period in a woman’s life, is so important is because estrogen, the hormone that fluctuates during the perimenopause and then reduces and declines in post-menopause, has effects all over our body. Nearly every cell in our body has estrogen receptors. So our brain, our blood vessels, nearly everywhere.

So this roller coaster of estrogen during the perimenopausal phase and also the reduction post-menopausally has far-reaching health effects. So for example, post-menopausally, women are five times greater risk of having a heart attack. Now, some of that’s due to age, but it’s also due to the loss in estrogen. Women are five times more likely to have abdominal obesity, which is fat around the tummy.

And that’s because of estrogen’s role in fat tissue deposition, so where fat tissue is deposited. We see in our own zoopedic research, pre-menopause, women are doing well compared to men in terms of many of these, what we call intermediary risk factors of cardiovascular disease, blood pressure, cholesterol, glucose, insulin, etc. As soon as they hit the menopause, suddenly they catch up with men and it gets worse. And so suddenly their blood pressure is higher than men or their cholesterol is the same level as men.

So we see this as well in our zoopedic research that post-menopausally and perimenopausally, people’s cholesterol and their bad cholesterol, their LDL cholesterol increases by 25%. And this is all related to the wide-reaching role that estrogen has in our body. We also see that estrogen impacts, and therefore the perimenopause and postmenopause, how we metabolize food. So we see bigger excursions in post-meal glucose and post-meal fat after the menopause. Again, it’s all linked to the role that estrogen plays in our metabolism.

And then I think what’s most important to be aware of regarding the perimenopause and postmenopause phase is the symptoms that women experience. And we’ve done some research in 70,000 individuals where we’ve looked at how prevalent these symptoms are. We see that 99% of perimenopausal women experience at least one menopausal symptom. We see that 66% of perimenopausal women have 12 symptoms or more. And this has a huge burden. We know from other surveys, 10% of women leave the workforce during the perimenopause and postmenopausal phase because of the burden that these symptoms have on their quality of life.

STEVEN BARTLETT: And what age does this typically occur, the perimenopausal symptoms?

DR SARAH BERRY: So typically people become menopausal, as in postmenopausal stop their menstrual cycles at 51. The menopausal transition period can be anything from 2 to 10 years. Typically, people would say maybe around the ages of 47, many women start to experience perimenopausal symptoms. And these include symptoms like brain fog, anxiety, memory loss, irritability, low libido, change in metabolism.

And now I’m in that perimenopausal phase and have forgotten all of the others, but there’s about 50 symptoms that are recognized. And we see in our own research that the amount of women experiencing symptoms is really high. So we see that 85% of women are saying they have brain fog, they have anxiety, they have memory loss. It’s really high, the amount of women experiencing these symptoms.

And what’s really interesting is we know, yes, HRT, so hormone replacement therapy, or MHT, can help reduce many of these symptoms. But we also know that diet can help as well. And I think actually seeing one of the most interesting things from our research, looking at menopause and symptoms, is that typically when we think of menopausal symptoms, we think about hot flushes. And if I was to ask you, actually I wish I’d have asked you before I said that, but if I was to ask you, if you were to think of a menopause symptom, what would come to your mind first?

STEVEN BARTLETT: I would say hot flushes, because that seems to be the only time that people talk about hot flushes is when they’re talking about menopause in my world. And then I’d say brain fog.

DR SARAH BERRY: Yep. And what’s really interesting is hot flushes are one of the least common symptoms. About 40% of women in our research have hot flushes, 85% have brain fog, 85% have all of the other brain-related symptoms. And yet typically we always think about hot flushes. And this is because there just hasn’t been loads of research on menopause. And so I think what’s really exciting is there is now a lot more research on menopause.

So I think the future is really exciting. But I think what comes with this is yet more neutropilics.

STEVEN BARTLETT: Mm-hmm.

DR SARAH BERRY: And that’s because I think there’s this whole area of what we call menowashing. I don’t know if you’ve heard of menowashing.

STEVEN BARTLETT: No, I haven’t.

DR SARAH BERRY: Stick meno for menopause in front of any product you can charge 10 times as much. I could call this a menopause tea. It’s actually Yorkshire tea, and it’s a very good cup of tea. I could call this a meno tea and charge 10 times as much for that teabag without any evidence. Because women are desperate, 45% of women say their symptoms are so burdensome they’ll try anything. 10% leaving the workforce because of their symptoms.

And so we have to be really careful that we are only selling evidence-based supplements for which there isn’t much evidence at the moment. And I think that the evidence that an overall healthier dietary pattern can reduce symptoms is the best way forward for now, alongside for those who choose to hormone replacement therapy.

STEVEN BARTLETT: A recent survey showed that 30% of menopausal women are trying herbal remedies, 30% are trying vitamins, and 51% are trying any kind of dietary therapy as an alternative to HRT. That was in iNews, which supports what you’re saying, that there’s lots of people searching.

Because I think from the experiences that I’ve had with people talking to me about menopause, it seems to be an incredibly confusing period of life where you can’t make sense of what’s happening. And all the old rules of just, you know, hit the gym and eat a bit healthier seem to go out the window. Because there’s something deeper at play in your body. So it’s not that you’re not eating right, or it’s not that you’re not sleeping right. It’s a deeper hormonal fluctuation that you’ve actually never experienced before. So of course, you’re going to be really confused and quite easily gaslit as well, I imagine, because, you know, I’ve had someone say to me that they felt like they were going crazy. And then people started thinking they were just like, kind of going crazy a little bit.

DR SARAH BERRY: Yeah, I think, you know, fortunately, I think it’s changing. But historically, we didn’t talk about it. You know, I vaguely remember my mum saying, I’m having hot flush. But we didn’t talk about menopause, we didn’t talk about periods, we just didn’t talk about it in that, you know, when I was growing up. And unfortunately, my mother’s no longer alive. So I don’t really know what she did go through. And I want to talk about it. People are talking about it. We have people like Davina McCall, who are amazing, because they’re getting women talking about it.

So we’re no longer ashamed. So I think the tide is really turning. But menopause is this perfect storm, because you have these burdensome symptoms. And then you have alongside it, which I don’t think we talked about enough is these health effects that I talked about.

So women going through menopause aren’t sleeping. I mean, my sleep is all over the place. Honestly, when I get a good night’s sleep, Stephen, I feel like superwoman. It reminds me of the state I’m in at the moment is like how I was when I had kids, where, you know, I get in four or five hours sleep, then I wake up, if I’m lucky, I might get back to sleep.

So you’ve got women, they’re not getting enough sleep. You’ve got women who often are feeling a bit depressed or anxious or, you know, losing their confidence because of their brain fog because of their memory loss because of you know, their anxiety. You’ve got the hormones changing your body composition. Suddenly you’re eating and doing everything the same. But all the fats being directed to your tummy, your hunger signals are mucked up, your desire to eat different food changes. And we see this again in our own research that postmenopausal women tend to eat a lot more sugary foods than premenopausal women.

So you’ve got this perfect storm of things going on. And then in amongst that, do you really want to do some physical activity? Are you really motivated to start eating healthier? And, you know, when you’re exhausted, it goes back again to that importance of sleep and that interaction of sleep with our food choices and how we respond to food. There’s so many things to think about. And I think it’s really tough in that peri and postmenopausal phase when your body’s changing, when you’re tired, when you’re feeling a bit rubbish to also take control of your diet.

But it’s the most important time because it’s when your cholesterol increases. It’s when your blood pressure increases. It’s when all of this fat tissue around your belly is releasing harmful inflammatory chemicals, etc. So it’s when, unfortunately, we really do need to take stock of our physical activity, of what we’re eating, and our stress levels. But it’s probably one of the most challenging times to do it as well.

STEVEN BARTLETT: You must be incredibly stressed through that period, but also just thinking about your relationships. If you’re in a relationship in a heterosexual marriage with a husband who isn’t going through that at that period of their life, and you said there was a libido issue that’s symptomatic of menopause as well, to navigate all of that and for the people around you to understand what’s going on in your head must be incredibly stressful, incredibly stressful. I’m very, I feel very, I don’t know what the right words are here, but I feel very sympathetic because I can’t imagine, I don’t think there’s a point in the man’s life where we go through such a profound change in our hormones in such a confusing way all of a sudden.

Impact of Menopause on Relationships

DR SARAH BERRY: But I think, Steven, if we raise awareness so that men are aware and they can support their partners, and libido, as an example, we see in our own research, whilst it might not be the most common, women rate it as the most burdensome. So we monitor not just the prevalence, so how common the symptoms are, we also ask people how much impacts their quality of life. And the peri and post-menopausal women rate that as their symptom that has the most burden on their life. Because if I’m not slept and I’m not feeling sexy, I’m independent of whether there’s a chemical impact on my hormone levels that causes my lowering of libido, I’m not trying to have sex.

STEVEN BARTLETT: You want to go to sleep.

DR SARAH BERRY: I want to go to sleep, yeah, exactly. So even if, you know, and especially I don’t feel good, I don’t feel sexy, I’m probably, my mood might be altered.

STEVEN BARTLETT: Yeah, your tummy’s probably grown.

DR SARAH BERRY: Yeah, it’s not going to be.

STEVEN BARTLETT: So what advice do you give to those women going through that? You said that you’re on hormone replacement therapy yourself previously, and that’s had, I guess, a positive impact on your menopause journey.

DR SARAH BERRY: Yes, I still sleep really badly. I don’t think HRT is the answer for everyone, and some people can’t take it if they’re contraindicated with certain risk related to cancer, and some people choose not to take it, and it certainly doesn’t solve everything. I do think the evidence is very compelling for reduction in many symptoms. I think the evidence is compelling or increasing and building for the beneficial effects it also has on some of the health effects that happen during menopause, like blood pressure, cholesterol, tummy fat.

So I’ve chosen to take it for both health and for symptoms, but there’s reasonable evidence now showing that diet can help reduce symptoms. There isn’t a one-size-fits-all, there isn’t a silver bullet, but an overall healthier dietary pattern, I believe, can reduce menopause symptoms. This comes from other published research as well as our own research that we’ve done at ZOE, where we’ve looked in a subgroup of individuals over a 12 to 18 week period and looked at those who transitioned to a healthier diet.

They’re actually following the ZOE program, but the underlying principles are the same for all individuals to follow a healthy diet, so increased plant diversity, increased fibre, a very kind of Mediterranean style diet. And what we see in those people who are improving their diet, they have 35% reduction in symptoms. Now that’s huge. I do have to caveat that to say, though, that there wasn’t a control arm. So it’s not a clinical, an RCT, as we call it. It’s a study where we followed people at one point in time and collected data at another point in time.

What we now need to do is repeat this with a control arm to see if we see the same size effect. But there are other studies that have, in a randomised control trial, asked people to follow the Mediterranean diet or a controlled diet, and they see a similar magnitude of around 30% reduction in symptoms, which is huge and promising, I think.

But I think where we have to be really careful with menopause, because we are desperate, because we’re struggling, I think we’re really susceptible to marketing, to this menowashing. And I think there are so many supplements that are being sold, the silver bullet, you know, and I see it on social media. And I think firstly, okay, if it works for you, great. If you can afford it, great. But what worries me is people who are spending a lot of money that they could be using for a healthy dietary pattern, or, you know, a gym membership or whatever on a supplement that there is no evidence to support. And the evidence is very, very weak.

Except for a supplement called soy isoflavones, there is very weak evidence that any other supplements will work consistently. They might work for some people, but consistently.

STEVEN BARTLETT: Soy isoflavones?

DR SARAH BERRY: Yep. So soy isoflavones are a particular chemical that are found in some foods. It’s a chemical that has a structure very similar to oestrogen, so actually binds to the oestrogen receptors in the body, which is why it has a beneficial effect on many symptoms. Now, soy isoflavones are consumed in quite small amounts in the UK. In the US, we consume probably about one milligram a day on average.

In the Far East, like China, they consume about 70 milligrams a day as part of the natural diet. So in those kind of countries, they actually have a really low prevalence of menopause symptoms compared to us. They still have menopause symptoms, but it’s a bit lower than us. What we know is that if you supplement people with soy isoflavones, for the vast majority of people, but not everyone, it will reduce symptoms a little bit. Not totally, but it can reduce symptoms.

STEVEN BARTLETT: And is your underlying health a predictive factor of the amount of symptoms you’ll experience? If I’m obese and then I go into perimenopause, are my symptoms going to be more significant?

DR SARAH BERRY: So that’s a good question. We’ve looked at how living with obesity can impact your symptoms, and we do see that if you’re living with obesity, you have a higher number of symptoms. We see that if you have an unhealthy diet to start with, you have a higher number of symptoms. We see that if you have low physical activity, you smoke, etc., yes, it’s associated with higher symptoms. This is all association data though, it doesn’t show causality, and it’s really important to say that.

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STEVEN BARTLETT: What is the most important thing we should have talked about that we haven’t talked about, Professor?

DR SARAH BERRY: I think we’ve covered an awful lot. And I think the thing that I would emphasize when people are thinking about their health, thinking about their diet, is first to find what works for you. Find something you enjoy. But I think I would say be really, really careful of the misinformation that’s out there. Really careful. And I would say also, if you’re going to make a change, make sure it has a big enough size impact to warrant the change you’re making.

Because there’s a lot of advocates for this health optimization. Make this change, and it will have this impact. Well, if you’re making a change that disrupts your life significantly, but only has a 1% impact on whatever health outcome you’re interested in, whether it’s your cholesterol, your overall energy, or whatever, is it really worth disrupting your life that much for that small change? And I think that’s really important.

I hear so many times when I’m talking to other mums at Schoolgate or that sort of thing, oh my gosh, I read this, and I’m going to do this. And it’s going to be really hard, but they said it will help with this. And it’s like, oh, you’re taking away pleasure. And actually, what is the gain?

STEVEN BARTLETT: And if the world is to move forward in a way that is positive in your estimation, how does the world change and improve as it relates to all the subjects we’ve talked about today? What is that change you wish to see in the world in which you operate?

DR SARAH BERRY: I would love to see a world where scientists, food industry, and policy makers work together. I’d love to see a world where we encourage evidence-based science, but scientists aren’t scared of working with food industry, for example.

STEVEN BARTLETT: A lot of people think the food industry is bad, like it’s this sort of evil guy who sat in this boardroom who’s just counting money and just pushing whatever these little innocent children will put in their mouths and to make them addicted and give them neurodivergence and all kinds of other issues, potentially. A lot of people feel that the food industry has become this sort of singular entity people think about in the sort of conspiracy theory internet. And you kind of imagine it is like a guy in a boardroom suit who’s just like cackling and laughing and stuff like that.

DR SARAH BERRY: I think that I can’t comment on their motivations for profit. I don’t think I’m informed enough to comment on that. But I do believe that the food industry needs to work with academia in order to solve the problem of the kind of foods that are out there. We need impact from government as well. We need impact from policy makers. We need to go back to grassroots. We need to be educating our children how to cook. We need to be giving healthy school meals. We need to be educating them in schools. What is a healthy meal? What isn’t a healthy meal? What is a healthy food?

But I think that something that’s so important is this current state of fear, I think we’re in a perilous state at the moment of there are some people making a lot of noise in the media about scientists working with industry, how any research funded by industry is therefore biased, corrupt, can’t be trusted. That’s certainly not my experience. It’s not what I have ever seen from any other colleagues taking money from food industry in order to do studies.

We as nutrition scientists need to do studies. We need to run clinical trials in order to look at how we can improve the food to make it healthier. The amount of funding we get from independent government bodies is tiny. To get funding, the amount of time we have to spend as academics writing grants to be rejected and rejected because the government invests so little in nutrition research.

We need to be able to get funding to be able to run studies to answer important questions. The money and the experience I’ve had from those around me, when we receive funding from research, when we receive funding from industry, there is very limited involvement that they are allowed to have with what we do. The university ensure that. We conduct the research, we do the analysis, we publish the paper. The industry funders cannot get involved in that process. I still see it as independent.

Now, there is discussion about are they setting the agenda of that research? There’s something we could talk about for days and days, but I think this narrative that’s out there that just because a study is being funded by the food industry is biased is wrong. I think it’s unhelpful. It’s putting these exposés that certain media personalities are putting forward that if an academic has taken money from the food industry, that therefore they cannot be advising us on food, they cannot be trusted for their research. I think that that’s a real problem for us as nutrition scientists because it’s creating a time of fear.

STEVEN BARTLETT: When you explain it through how these studies get funded, then it makes a ton of sense. Actually, part of what I was thinking is the government should be doing a little bit more to fund these kinds of studies because I don’t really believe that we’re going to get the food industry to work together. Again, thinking about incentives, if there’s one cereal company here and the other here, and let’s say there’s 10 of them. Yeah, how can you get all of them to agree to take? Yeah, the two that don’t win, and then they keep their jobs, their companies are successful, they get a pat on the back.

When we think about health interventions that the government have made over the years that have been super effective, they’ve come from black policy. Smoking is a good example. I always think about the change in smoking in our society because they banned smoking indoors and put things on the packaging and just changed the social narrative and all smoking companies, tobacco companies have to sort of comply at once. That’s why I think all three have to work together. Government needs to take big responsibility now. But I think that there has to be an acceptance that academics, scientists can work with food industry and it doesn’t mean that-

DR SARAH BERRY: You’re correct. We’re corrupt or our results are biased in any way.

STEVEN BARTLETT: We have a closing tradition on this podcast where the last guest leaves a question to the next guest not knowing who they’re leaving it for.

A Simple Philosophy of Life

STEVEN BARTLETT: And the question that’s been left for you is, what is something that you believe that smart people you care about disagree with?

DR SARAH BERRY: Do you know what I believe? I believe that life can be simple, that actually all that matters is that you have good relationships, that you’re finding joy in life and that we shouldn’t overcomplicate things. And if on my gravestone I have written, Sarah was a nice person, I would be very happy with that.

But a lot of the clever people I interact with, I think, wouldn’t agree that that’s necessarily a good achievement in life. But I see that as a great achievement.

STEVEN BARTLETT: What do you think they might want written on their gravestone instead? You’re smirking nervously.

DR SARAH BERRY: I am.

STEVEN BARTLETT: Is it that you’re obsessed with like impact and ego and those kinds of things? Is that what you’re saying?

DR SARAH BERRY: I don’t know because the people that I care about, I don’t think are egotistical. I think we live in a society, certainly in a society where we’re mixing with successful people, where there is a lot of ambition, where there is a lot of emphasis put on your achievements, where there’s a lot of striving for the next goal, striving for the next achievement.

And maybe it’s having had four years where I took a career break, where I was caring for my mum. And together with the rest of my family, we looked after my mum, we kept her at home through a degenerative neurological condition. And seeing someone change, seeing someone lose the power to talk, lose the power to eat, lose the power to interact, lose the power to do everything that we take for granted, I think has enabled me to not sweat the small stuff.

It’s enabled me to find joy in most things, pleasure in most things, and not strive for things that maybe in the past I would have.

STEVEN BARTLETT: Perspective.

DR SARAH BERRY: I think it’s given me a perspective. Now, don’t get me wrong. You know, I was nervous before coming on here. So I sweated about that. And, you know, I’m not saying that I’m always like, horizontally laid back by any means. But I think it’s given me a perspective on what matters to me.

And what matters to me, and I think the greatest achievement in my whole life has been actually not becoming professor, which I’m incredibly proud of. I’m from a working class family. You know, I was the first person in our family to ever go to university. My mum and dad didn’t have the privilege of staying at school beyond 14.

And I mean, it saddens me that they hadn’t seen this success, saddens me very much. And whilst the pride I felt yesterday at the ceremony was phenomenal, actually, what I’m most proud of is the four years that I cared for my mum. And to me, that’s what matters. And so that’s why when I’m with lots of smart people, and I think they’re doing amazing things. I don’t have the same perspective sometimes. I probably don’t care as much. It’s almost I’m having fun.

And you know what, and I think I said this at the beginning, I’m so privileged. I get to do my hobby every day. I love what I do. I’m not doing this necessarily because I’m such a selfless person that I want to improve everyone’s health. Yes, if that’s a by-product, great. But I get up and I love what I do. I’m so excited by the science that we do.

And what drives me to do it is having been through that situation of realising how delicate life is. So just seize the moment. Enjoy what you’re doing at that point in time.

STEVEN BARTLETT: Thank you so much, Professor. Congratulations. I didn’t realise you had the ceremony yesterday. That’s an incredible achievement. I know that we’re not prioritising the achievements as much anymore, but it’s incredible. Yeah, it’s an incredible thing. And it’s a credit to the work that you’ve done and how you’ve done it over the last 25 years and the broader impact I think you’ve had on so many millions of people’s lives now through now the content you’ve put out.

Thank you so much for doing the work that you do. Thank you for illuminating so many of these subjects to me today. I actually sent a message to my team before saying that I’ve had lots of conversations about nutrition and stuff, but the primary research you’ve done and the research you’re continuing to do is so much of it’s completely new to me. And that’s quite hard when I sit here doing this every day.

It’s been amazing. Thank you. It’s been an absolute joy speaking to you, not just from the information standpoint, but from the broader philosophical idea of how one should approach their life and how one can approach their life has been incredibly inspiring. So thank you.

DR SARAH BERRY: Thank you. It’s been a real pleasure to talk about so many things I’m passionate about.

STEVEN BARTLETT: We shall do it again sometime. Thank you.

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