Colorectal cancer is the second leading cause of cancer death in the United States, after lung cancer. The rates of lung cancer around the world vary by a factor of 10, showing us that there are external causes, i.e. smoking.
There is an even bigger variation for colon cancer. It appears that colon cancer does not just happen, there is something that makes it happen. 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 the answer the question why native Africans have 50 times lower rates of colon cancer than rates of Americans, white or black.
Dr. Denis Burkitt believes that it has something to do with their staple diet traditionally high in whole grains and fiber. It seems that people get a 10% reduction in risk for every 10 grams of fiber they eat a day. If it’s a 1% drop for each gram, and Africans eat upwards of 100 grams a day, it could explain why colon cancer is so rare in sub-Saharan Africa.
Yet, the modern African diet is highly processed and low in fiber, yet there still has been no dramatic increase in colon cancer. Today, the African diet is much different from how it used to traditionally be. Their diet has such a low fiber content because most populations now depend on commercially produced refined cornmeal. Their fiber intake is just about as low as that of people in the United States, around half the recommended daily allowance. Yet colon disease in Africa is still about 50 times less common than in the United States.
There is one difference in diet between Americans and Africans. The North American diet is high in meat, while the African diet is low in meat and saturated fat. Native Africans have total cholesterol levels averaging 139 mg/dL, compared to over 200 mg/dL in the United States.
The minimal consumption of meat and animal fat could be what keeps colon cancer at bay. The rarity of colon cancer in Africans is probably not fiber, but their low animal product consumption instead.
While opinions on whether cholesterol, animal fat, or animal protein are responsible for the increased colon cancer risks or not, there is a proof that all have carcinogenic properties.
Phytates play a critical role in the prevention of cancer. Resistant starch may be another player. Since native Africans cool their corn porridge down, some of the starch can crystalize and effectively turn into fiber.
Yet fiber could just be a marker for healthier eating since it is only found concentrated in unprocessed plant foods. The apparent protection afforded by high fiber diets may derive from whole food plant-based nutrition rather than the fiber itself.