Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Colon cancer is our second leading cancer killer, but some places, like rural Africa, have more than 10 times lower rates than we do. The reason we know it’s not genetic is that “[m]igrant 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 are 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 find out why colon cancer rates were an order of magnitude higher here—in African-Americans and Caucasians—than in rural Africa. If you look at American colons, they’re a mess: polyps, diverticulosis—not to mention hemorrhoids— whereas the African colons were “remarkably pristine.” And more importantly, sevenfold lower colonic epithelial proliferation rates, a characteristic of precancerous conditions. They measured everything 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. “The higher rates are associated with higher animal protein and animal fat, and lower fibre 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 the poor Africans get the SAD, Standard American Diet—like sausage and white flour pancakes for breakfast, a burger and fries for lunch, and 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 compliance, 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 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 was in overdrive, the cells rapidly dividing, a sign of premalignancy, 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 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. Impressively, “Africanization” of the diet more than doubled butyrate production, whereas “westernization” cut it in half. And in terms of toxic metabolites, a significant drop on the healthier diet, whereas the meatloafy diet increased the levels of these carcinogens by 400 percent 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 risks 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 healthful longevity.”

Please consider volunteering to help out on the site.