Preventing Colon Cancer

There’s been some alarming news about colon cancer recently. Did you know that colon cancer is the number 1 cancer killer among non-smokers and that people seem to be getting it earlier and earlier in life? Today, we look at the best diet for a healthier colon.

We have “100 trillion micro-organisms” residing in our gut, give or take a few trillion, but “the spread of the Western lifestyle has been accompanied by microbial changes,” which may be contributing to our epidemics of chronic disease. The problem is that we’re eating these meat-sweet diets, characterized by “a high intake of animal products and sugars, [processed foods], and a low intake of [whole plant foods].”

Contrary to the fermentation of the carbohydrates that make it down to our colon—the fiber and resistant starch that benefit us “through the generation of [these magical] short-chain fatty acids” like butyrate—”microbial protein fermentation [when excess protein is consumed…that] generates potentially toxic and pro-carcinogenic metabolites involved in [colorectal cancer].” And so, what we eat can cause an imbalance in our gut microbiome and potentially create “a ‘recipe’ for colorectal cancer,” where a high-fat, high-meat, high-processed food diet tips the scale towards dysbiosis and colorectal cancer, whereas a high-fiber and -starch, lower-meat diet can pull you back into symbiosis with your friendly flora, and away from cancer.

We now have evidence from interventional studies suggesting that “adopting a plant-based, minimally processed, high-fiber diet may rapidly reverse the effects of meat-based diets on the gut microbiome.” So, what might be “a new form of personalised…microbiome…medicine for chronic disease”? It’s called food, which can “rapidly and reproducibly alter…the human gut microbiome.” Switch people between a whole food plant-based diet and more of an animal food-based diet, and you can see dramatic shifts within two days, which can result in toxic metabolites. Switch people to an animal food-based diet, and levels of deoxycholic acid go up, which is “a secondary bile acid known to promote DNA damage” and liver cancers. Why do levels go up? Because the bad bacteria producing the stuff triple—in just two days.

And, over time, the richness of the microbial diversity in our gut is disappearing. “A low-fiber diet is a key driver of microbiome depletion.” Yeah, there’s antibiotics, and Caesarean sections, and indoor plumbing, but “the only factor that has been empirically demonstrated to be important is a diet low in…MACs (not Big Macs), “microbiota-accessible carbohydrate,” which is just a fancy name for fiber found in a whole plant foods and resistant starch, found mostly in beans, peas, lentils, and whole grains.

Our “intake of dietary fiber,” our intake of whole plant foods, “is negligibly low in the Western world” when compared to what we evolved to eat over millions of years. “Such a low-fiber diet provides insufficient nutrients for [our] gut microbes, leading not only to the loss of [bacterial diversity and richness], but also to a reduction in the production of [those beneficial] fermentation end products…” that they make with the fiber. We are, in effect, “starving our microbial self.”

What are we going to do about “the deleterious consequences of a diet deficient in” whole plant foods? Create new-fangled “functional foods,” of course, and supplements, and drugs—prebiotics, probiotics, synbiotics. Think how much money there is to be made! Or, we could just eat the way our bodies were meant to eat. What kind of value is that going to get your stockholders, though? Don’t you know probiotic pills may be “the next big source” of Big Pharma billions?

Why eat healthy though, when you can just have someone else eat healthy for you, and then get a fecal transplant from a vegan! Researchers compared the microbiomes of vegans versus omnivores, and found the vegan’s friendly flora were churning out more of the good stuff, showing that a plant-based diet may result in more beneficial metabolites in the bloodstream and less of the bad stuff like TMAO. But while the impact of a vegan diet on what the bacteria were making was “large,” the “effect on the composition of the gut microbiome [was] surprisingly modest.” They “only [found] slight differences between the gut microbiomes of omnivores [versus] vegans”? That was a shocker to the researchers; this “very modest difference…juxtaposed against the significantly enhanced dietary consumption of fermentable plant-based foods.” The vegans were eating nearly twice the fiber. Anyone see the problem here? The vegans just barely made the minimum daily intake of fiber. Why? Because Oreos are vegan, Cocoa Pebbles are vegan, French fries, Coke, potato chips; there are vegan Doritos and Pop-Tarts. You can eat a terrible vegan diet.

Burkitt showed that you need to get at least 50 grams a day (of fiber) for colon cancer prevention. And that’s only half of what our bodies were designed to get. We evolved getting about 100 grams a day. And that’s what you see in modern populations that are immune to epidemic colorectal cancer. So, what if instead of feeding people a vegan diet, you just fed people that kind of diet, a diet centered around whole plant foods? We’ll find out, next.

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.

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 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. “The 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, 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.”

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.”

In our next story, we look at how modern African diets may now be as miserably low in fiber as American diets, but they still have less cancer than we do.

Colorectal cancer is the second leading cause of cancer death in the United States, after lung cancer. If you look at the rates of lung cancer around the world, they vary by a factor of 10. If there were nothing we could do to prevent lung cancer, if it just arose spontaneously, happened at random, you’d assume that the rates everywhere would be the same. But since there’s such a huge variation in rates, you assume there’s some external cause, and indeed, we now know smoking is responsible for 90 percent of lung cancer cases. So, if we don’t want to die of the #1 cancer killer, by just not smoking we can throw 90 percent of our risk out the window. For colon cancer, there’s an even bigger spread, bigger variation around the world. So, it appears colon cancer doesn’t just happen; something makes it happen. Well, if our lungs can get filled with carcinogens from smoke, maybe our colons are getting filled with carcinogens from food. Researchers from the University of Pittsburgh and the University of Limpopo sought to answer the question, “Why do African Americans get more colon cancer than native Africans?” Why study Africans? Because colon cancer is extremely rare in native African populations, like more than 50 times lower than rates of Americans, white or Black.

It’s the fiber, right? Dr. Burkitt was the first to describe the low incidence of colon cancer in native Africans, ascribing it to their traditional staple diet that was high in whole grains and, therefore, fiber content. Seems you get about a 10 percent reduction in risk for every 10 grams of fiber a day. So hey, if it’s a 1 percent drop for each gram, and they’re eating upwards of 100 grams a day, that could explain why colon cancer is so rare in sub-Saharan Africa.

But wait a second, the modern African diet is highly processed, low in fiber, and yet there has been no dramatic increase in colon cancer incidence.

The modern African diet has a low fiber content, as most populations now depend on commercially-produced refined cornmeal. And we’re not just talking low fiber intake; we’re talking United States of America low, down around half the recommended daily allowance. Yet, colon disease still remains rare: still 50 times less colon cancer.

Maybe it’s because they’re thinner and exercise more? No, they’re not, and no, they don’t. If anything, their physical activity levels may now be even lower. So, if they’re sedentary like us, eating mostly refined carbs, few whole plant foods, little fiber—like us–why do they have 50 times less colon cancer? Well, there is one difference. The diet of both African Americans and Caucasian Americans is rich in meat, whereas the native African diet is so low in meat and saturated fat they have total cholesterol levels averaging 139, compared to over 200 in the U.S.

So yes, they don’t get a lot of fiber any more, but they continue to minimize meat and animal fat consumption, 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 not the fiber, but their low animal product consumption.

There is a divergence of opinion as to whether it’s the animal fat, cholesterol, or animal protein that is most responsible for the increased cancer risk, as all three have been shown to have carcinogenic (cancer-causing) properties, but it may not really matter which component is worse, as a diet rich in one is usually rich in the others.

Finally today, the fermentation of fiber in the gut may help explain the dramatic differences in colorectal cancer incidence around the world.

More than 30 years ago, an idea was put forward that high colonic pH promoted colorectal cancer. A high colonic pH may promote the creation of carcinogens from bile acids, a process that is inhibited once you get below a pH of about 6.5. This is supported by data showing those at higher risk for colon cancer may have a higher stool pH, and those at lower risk, a lower pH. There was a dramatic difference between the two groups, with most of the high-risk group, pH over 8, and most of the low-risk group, pH under 6.

This may help explain the 50-fold lower rates of colon cancer in Africa compared to America. The bacteria we have in our gut depends on what we eat. If we eat a lot of fiber, then we preferentially feed the fiber-eating bacteria, which give us back all sorts of health-promoting substances like short-chain fatty acids, which have anti-inflammatory and anti-cancer properties. More of these organic acids were found in the stools of native Africans than African Americans. More acids, so lower pH. Whereas putrefactive bacteria, eating animal protein, are able to increase stool pH by producing alkaline metabolites like ammonia.

The pH of the stools of white versus Black children in Africa was compared. Children, because you can more readily sample their stools–particularly the rural Black schoolchildren who were eating such high fiber diets (whole grains, legumes, nuts, vegetables, fruits, and wild greens) that nine out of ten could produce a stool on demand. Stuffed from head to tail with plants, they could give you a stool sample at any time, as easy as getting a urine sample. Hard to even get access to the white kids, though, who were reluctant to participate in such investigations, even though they were given waxed cartons fitted with lids, and all the Black kids got was a plate, and a square of paper towel.

What’d they find? Significantly lower fecal pH in those eating the traditional rural plant-based diets, compared to those eating the Western diet, who were eating far fewer whole plant foods than the Black children. But remove some of those whole plant foods, like switch their corn for white bread for just a few days, and their stool pH goes up. And add more whole plant foods, like an extra five to seven servings of fruit every day, and their stool pH goes down even further, gets more acidic. Makes sense, right? What happens when you ferment plants–fruits/veggies/grains? They turn sour, like vinegars, sauerkraut, sourdough, because good bacteria–like lactobacillus–produce organic acids, like lactic acid. And those who eat a lot of plants have more of these good bugs in their system. So using the purple cabbage test, we want blue pee, but pink poo.

No surprise, then, if you compare the fecal samples of those eating vegetarian or vegan to those eating standard diets. Plant-based diets appear to shift the makeup of the bacteria in our gut, resulting in a significantly lower stool pH, and the more plant-based, the lower the pH dropped. It’s like a positive feedback loop. Fiber-eating bacteria produce the acids to create the pH at which fiber-eating bacteria thrive, while suppressing the group of less beneficial bugs.

How long does it take to bring stool pH down on a plant-based diet? As little as two weeks. A dozen volunteers carefully selected for their trustworthiness and randomized to sequentially go on regular, vegetarian, or vegan diets–and two weeks in, a significant drop in fecal pH was achieved eating completely plant-based.

But there are plant-based diets, and then there are plant-based diets. Remember these two groups? Dramatically different stool pH, yet both groups were vegetarian.  But the high risk group was eating mostly refined grains, very little fiber, whereas the low risk group was eating whole grains and beans, packed with fiber for our fiber-friendly flora to munch on.

Just as a reduction in high serum cholesterol contributes to the avoidance of coronary heart disease, so a fall in the fecal pH value may contribute to the avoidance of bowel cancer, and through the same means: eating more whole plant foods.