So yes, they don’t eat a lot of fiber anymore, but they continue to minimize meat and animal fat intake, supporting evidence that perhaps the most powerful determinants of colon cancer risk are the levels of meat and animal fat intake. So, why do Americans get more colon cancer than Africans? Maybe, the rarity of colon cancer in Africans is associated with their low animal product consumption.
But why? Did you ever see that take-off of the industry slogan, “Beef: It’s What’s For Dinner” – “Beef, It’s What’s Rotting in Your Colon”? I remember seeing that on a shirt with some friends, and I was such the party pooper, no pun intended — explaining that meat is fully digested in the small intestine, and never makes it down into the colon. It’s no fun hanging out with biology geeks but, it turns out, I was wrong.
It turns out, up to 12 grams a day of protein can escape digestion, and when it does, it reaches the colon, it can be turned into toxic substances, like ammonia. This degradation of undigested protein in the colon is called putrefaction; so, a little meat can actually end up putrefying in our colon. The problem is some of the by-products of this putrefaction process can be toxic.
The same thing happens with other animal proteins. If you eat egg whites, for example, some of that can putrefy, too. But, there’s protein in plants as well. The difference is that animal proteins tend to contain more sulfur-containing amino acids like methionine which is found concentrated in fish and chicken, and then eggs, less in beef and dairy, and much less in plant foods, which can be turned into hydrogen sulfide in the colon, the rotten egg gas that, beyond the smell, that can produce changes in the colon that increase cancer risk.
Now, there is a divergence of opinion as to whether it’s the animal fat, cholesterol, or animal protein that’s most responsible for the increased cancer risk, as all three has been shown to have carcinogenic properties. But, does it really matter since a diet rich in one is high in the others.
But the protein does more than just putrefy, though. Animal protein consumption causes an increase in blood levels of a cancer-promoting growth hormone called IGF-1. But, remove meat, egg whites, and dairy proteins from our diet, and our bloodstream can suppress cancer cell growth about eight times better. An effect so powerful, that Dr. Ornish and colleagues appeared to able to reverse the progression of prostate cancer without chemo, without surgery, without radiation; just a plant-based diet and other healthy lifestyle changes.
The link between animal protein and IGF-1 may help explain why those eating low-carb diets tend to die sooner, but not just any low-carb diet — specifically those based on animal sources, whereas, vegetable based low-carb diets are associated with a lower risk of death. But, meat based low-carb diets are high in animal fat as well; so, how do we know it wasn’t the saturated fat and cholesterol that was killing people off and had nothing to do with the animal protein?
What we would need is a study that follows a few thousand people and their protein intake for 20 years or so, and see what happens, who gets cancer, who doesn’t, who lives longer. But, there has never been a study like that…until now.
6,000 men and women over age 50, across the U.S, followed for 18 years, and those under age 65 with high protein intake had a 75% increase in overall mortality and a 4-fold increase in dying from cancer. But, not all proteins. Specifically, animal proteins, which makes sense given the higher IGF-1 levels in those eating excess protein. Eating animal protein increases IGF-1 levels, which increases cancer risk.
The sponsoring university sent out a press release with a memorable opening line: “That chicken wing you’re eating could be as deadly as a cigarette,” explaining that eating a diet rich in animal proteins during middle age makes you four times more likely to die of cancer — a mortality risk factor comparable to smoking. And look, everyone is going to have a cancer cell or pre-cancerous cell in them at some point. The question is: does it progress? That may depend on what we eat. See, most malignant tumors are covered in IGF-1 receptors, but if we have less IGF-1, the tumor may not progress.
And, it wasn’t just more deaths from cancer. Middle-aged people who eat lots of proteins from animal sources were found to be more susceptible to early death in general. Crucially, the same did not apply to plant proteins like beans, and it wasn’t the fat, it was the animal protein that appeared to be the culprit.
So what was the response to this revelation that diets high in meat, eggs, and dairy could be as harmful to health as smoking? One nutrition scientist replied that it was wrong, and potentially dangerous. Not the discovery that animal protein may be killing people, but the way they were telling people about it; it could damage the effectiveness of important public health messages. A smoker might think: ”why bother quitting smoking if my cheese and ham sandwich is just as bad for me?”