 Colon cancers are second-leading cancer killer, but some places, like rural Africa, are more than 10 times lower rates than we do. The reason we know it's not genetic is that migrant studies, such as those in Japanese Hawaiians, have demonstrated that it only takes one generation for the immigrant population to assume the colon cancer incidence of the host Western population. Now, the change in diet is considered most probably responsible for this, but there's all sorts of changes when you move from one culture to another, like smoking rates, different exposures to chemicals, infections, antibiotics. You don't know if it's the diet until you put it to the test. It's rare I do a whole video on a single study, but I think you'll agree this one is worth it. This international group of researchers were trying to figure out why colon cancer rates were an order of magnitude higher here in African-Americans and Caucasians than in rural Africa. Well, if you look at American colons, they're a mess. Polyps, diverticulose, and not to mention hemorrhoids, whereas the African colons were remarkably pristine, and more importantly, seven-fold lower colonic epithelial proliferation rates, a characteristic of pre-cancerous conditions. They measured everything that they were eating and concluded that the higher colorectal cancer risk and proliferation rates were most closely associated with higher dietary intakes of animal products, which may have led to higher colonic populations of these potentially toxic acid and bile salt-producing bacteria, but you don't know until you put it to the test. Higher rates are associated with higher animal protein and animal fat and lower fiber consumption. More of those bad bile acids, less of those good short-chain fatty acids, like butyrate, and that higher mucosal proliferation. But how do we know it's the diet that's mucking things up? You don't know until you perform an interventional study. How about we just swap their diets, feed the Americans a high-fiber African-style diet, and those poor Africans get the sad, standard American diet, like sausage and white flour pancakes for breakfast, burger and fries for lunch, and like some meatloaf and white rice for supper. That was day one for the rural Africans in the experiment, whereas the Americans were forced to eat fruits and vegetables, corn and beans. To help with complies they threw in more familiar foods, like veggie dogs, though note it was not a vegan diet, just generally plant-based. And the food exchanges weren't for like years, but just two weeks. Could they see changes that fast? The dietary changes resulted in remarkable, reciprocal changes in the lining of their colons in terms of cancer risk and their microbiome, switching to plant-based, boosted the fiber fermentation and suppressed the carcinogenic bile acid synthesis? Let's look at some before and after pictures. They took biopsies, and this is the colon lining of an African-American under a microscope. Those brown dots mark dividing cells. Their colon lining wasn't overdrive. The cells rapidly dividing a sign of premolignancy, a risk factor for cancer, but just two weeks eating a healthier diet, and their colons calmed right down. The African Africans started out with some proliferation, but it got worse on the American diet. This is a different marker of measuring inflammation. Each of the brown dots here represents an inflammatory cell, so rife inflammation before calmed way down, after just two weeks, and the opposite in those eating worse. We know that when our friendly flora ferment fiber, they produce beneficial compounds like butyrate, which is anti-inflammatory and anti-cancer. Well, impressively, Africanization of the diet more than doubled butyrate production, whereas Westernization cut it in half. In terms of toxic metabolites, a significant drop in the healthier diet, whereas the meatloafy diet increased the levels of these carcinogens by 400% within just two weeks. So bottom line, no pun intended, what they were able to show is that just by changing the food, you can remarkably change your risk. In fact, that's how the lead investigator put it, change your diet, change your cancer risk. It may be never too late to start eating healthier. Based on these kind of data, adopting a whole food vegan or even just near vegan diet, rich in fruits and vegetables, along with other healthy lifestyle decisions, could have a stunningly positive impact on the cancer risk, not only of black Americans, but of all peoples. While it might be unrealistic to expect rapid and profound lifestyle changes in the general population, hey, at least we have sound, effective advice to offer to those who make the choice to take the steps needed to optimize their health and longevity.