Plants, The Microbiome, And Mental Health: Christopher A. Lowry (Transcript)

Here is the full transcript of neuroscientist Christopher A. Lowry’s talk titled “Plants, The Microbiome, And Mental Health” at TEDxMileHigh 2021 conference.

Listen to the audio version here:

TRANSCRIPT:

Check it out, spinach! You’ve probably eaten this hundreds of times, but did you know that on and inside this spinach plant are over 800 different species of bacteria? This is not about doing a better job of washing your veggies. These are bacterial endophytes, and you can’t wash them off, even if you try.

Plants are living organisms, and like us, they have microbiomes. These are thriving ecosystems of live bacteria and other microorganisms. I became fascinated by this fact about five years ago while collaborating on a paper about the American Gut Project. Researchers asked survey respondents, “In an average week, how many different plant species do you eat?”

Responses ranged from zero to over 30 plants in an average week. Now, normally nutritional guidelines measure nutrition intake in terms of volume. For example, how many cups of fruits and vegetables do you eat in a given day? But here, researchers, particularly in context of the gut microbiome, found that variety matters just as much, if not more.

The people who reported eating over 30 different plants in an average week have what we might consider an optimal gut microbiome with high diversity. Unfortunately, that’s not most of us. So I asked myself, “What would happen if I consumed 30 different plants a day?” That would be like eating the crop from a whole farm every day.

The 30 Plant Challenge

So I went to the grocery store, and I got 30 different plants, brought them home, rinsed them off, chopped them up, put them in a blender with six cups of water, and then I had 30 different plants a day for the next month. Then I did it again. Then I did it again.

These days, my nine-year-old daughter comes with me to the grocery store. It can be kind of fun to walk the aisles and pick out 30 different species of plants. I end up trying all kinds of new things, like sorrel or raw cactus. I’ve decided this is as close as I’m going to get to living the hunter-gatherer lifestyle.

I prepare a batch of this plant cocktail once a month, and then have a serving every evening with dinner. This has completely changed my life. By now, you might think that I’m some kind of nutrition junkie, but actually, I’m a neuroscientist, and I specialize in anxiety disorders, affective disorders like depression, and trauma and stressor-related disorders like post-traumatic stress disorder, PTSD.

Mental health is a hot topic these days, and for good reason. The Census Bureau and CDC report that approximately a third of Americans are reporting recent symptoms of anxiety and depression. We desperately need new ideas to solve our mental health problems at scale. The reason I’m interested in this plant cocktail is not because it’s nutritious, although it is, and not because it tastes good.

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Bacteria and Mental Health

You might think that it doesn’t, but because of up to 30,000 different species of bacteria in this plant cocktail, and what we’re learning about the relationship between bacteria and mental health. Whether you know it or not, sorry germaphobes, we breathe in and consume millions of bacteria every day, perhaps billions.

We’ve known about the beneficial effects of bacteria for some time now. There’s even a name for this idea, the “Old Friends Hypothesis.” If you think about it, the first mammals were burrowing animals that lived during the time of the dinosaurs. This means for at least the last 210 million years, mammals have co-evolved with soil bacteria.

Mammals were burrowing in the soil, breathing soil, consuming soil. These soil bacteria truly are our old friends. Now these bacteria can communicate with our brain through what’s called the microbiome gut-brain axis. There’s also evidence for a microbiome airway or lung-brain axis, and both seem to be important for maintaining our physical and mental health.

Bacteria can do all kinds of great things for us, from synthesizing vitamins to digesting fiber. What you need to know for this talk, however, is that many bacteria, including soil bacteria, can prevent inappropriate inflammation in our bodies. For example, growing up on a farm can protect you from developing allergic asthma later on in life. A recent study compared Amish and Hutterite children.

Farm Life and Inflammation

These two populations have a common ancestral origin in Europe; however, they’ve adopted different farming practices. Hutterite communities have adopted modern farming techniques, including the use of tractors to plow fields. Amish communities, on the other hand, have maintained traditional farming practices, including the use of large animals to help plow the fields.

Compared to an average American child, a Hutterite child has a reduced risk of allergic asthma. Amish children have an even lower risk of developing allergic asthma. And they were able to show that just this dust, when it was exposed to mice, was able to interact with the immune system in a way that prevented development of allergic airway inflammation.

Is it also possible that growing up on a farm can protect us from stress-induced inflammation, which we know is a risk factor for developing psychiatric disorders? To address this question, we partnered with Stefan Reber and his team at University of Ulm in Germany.

In this case, we recruited 40 healthy young men in Germany. Half of the men grew up on farms with farm animals for the first 15 years of their lives. The second half grew up in cities of at least 100,000 people without pets. We brought both groups into the clinic and asked them to give a speech in front of a camera and in front of a stern-looking panel of scientists in white lab coats.

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Stress and Inflammation

And I kid you not, giving a speech in front of a panel of scientists in white lab coats is one of the most stressful things that we can do to humans in the research laboratory.

What we found is that those that grew up on farms in the presence of farm animals had a lower inflammatory response when exposed to this purely psychosocial stressor.

This supports the idea that exposure to a diverse microbial environment like you find on a farm can not only protect against allergic airway inflammation, but may also protect against stress-induced inflammation, which we know is a risk factor for development of stress-related psychiatric disorders. So how far can we push this?

Can we strategically use bacteria to prevent psychiatric disorders? Twenty years ago, we injected mice with a bacterium that was isolated from the soil and the mud around Lake Kiyoga in Uganda. We already knew that this bacterium, Mycobacterium vaccae, when injected into mice could prevent allergic airway inflammation. We wanted to know if we inject mice with this bacterium, can we also see effects on the brain and can we see effects on emotional behavior?

What we found was mice that were injected with the bacterium had activation of serotonin neurons in the brain. They also acted as if we had injected an antidepressant drug. When we published this in 2007, this seemed really novel. But now, based on what we know about the microbiome gut-brain axis, this is not so surprising.

PTSD and Bacteria

This work led to a more recent study with Dr. Lisa Brenner and her amazing team at the VA right here in Denver, Colorado. For this study, we recruited US military veterans with a diagnosis of post-traumatic stress disorder and mild traumatic brain injury. Half of the veterans received a placebo.

Half of the veterans received a live bacterium that we know has anti-inflammatory properties. Veterans received the bacterium once a day for eight weeks. Then we brought them into the clinic and exposed them to the same psychosocial stress paradigm that I described earlier.

What we found is that those veterans who had received the bacterium responded with a reduced stress reactivity after exposure to the stressor. We also found that they had a reduced biological signature of inflammation. Although larger trials are needed, this supports the idea that we can use bacteria with anti-inflammatory properties for both the prevention and the treatment of trauma and stressor-related disorders like PTSD.

I believe that studies of the microbiome gut-brain axis have the potential to open up a whole new world of options for prevention and treatment of stress-related psychiatric disorders. For example, there’s a whole new field of psychiatry called “nutritional psychiatry.”

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Dietary Changes and Mental Health

A study was published in 2019, a meta-analysis of 16 separate studies showing that whole dietary changes could reduce anxiety and depression symptoms. And this was true in population studies, so people that were not depressed, but also in people with clinical depression. You might find that in the future, your doctor will provide a prescription for a special diet to reduce your symptoms of anxiety and depression.

You might also find that they’ll provide a prescription for a “green prescription” for increased exposure to nature as is currently being done in other countries. We might even find that in food deserts, we can find “30 packs,” variety packs of 30 different plants that people can just take home and incorporate into their diet. We might be able to develop a “farm in a pill,” or a “forest in a pill,” or even a shop where we can replace some of what we’ve lost by moving away from nature and into the cities.

Now research on bacteria and mental health is ongoing, but you can take advantage of what we know right now. There’s a big difference between the microbiome of someone who reports eating 5 or fewer plants in an average week, compared to someone who eats 10 plants, or 20 plants, or 30 plants, or even more plants in an average week.

Conclusion

You can literally eat your way to better mental health. The next time you go to the grocery store, put more plants in your grocery cart. Set up a competition with your friends and family to see if you can increase the number of different plants that you eat on an average week.

Get yourself and your family outdoors and exposed to nature as much as possible. Grow a garden. Bring more plants into your home. Get a dog. Pets are a great way to bring more bacteria into your home, and I mean that in the best possible way.

We’ve long known about the restorative effects of exposure to nature on our mental health. Perhaps it was always more than sunshine and fresh air at play. It makes us wonder if the future of mental health was right under our feet all along. Thank you.