Colorectal cancer is the most common gastrointestinal cancer and the second leading cause of cancer death in the United States. In fact, the National Cancer Institute estimates that in 2007 there will be approximately 150,000 new colorectal cancer cases with over 50,000 deaths.
African Americans have a high rate of colon cancer, occurring at a rate of 65 per 100,000. However, native African’s rate of colon cancer is far lower, occurring at less than 1 case per 100,000. Because African Americans have a rate 65 times higher of getting colon cancer than native Africans strongly suggests that differences in environment influence this disease.
Previous studies have shown that over 90% of gastrointestinal cancers are due to environmental influences such as diet. Strong epidemiologic and experimental evidence indicates that a diet high in red meat and animal fat is associated with an increased colon cancer risk.
Over 88,000 women aged 34 to 59 from the Nurses Health Study were examined to determine the link between diet and colon cancer. The analysis showed that those who frequently ate beef, pork, and lamb were 2.5 times more likely to develop the disease. Those who ate processed meats and liver were also at an increased risk, while those eating fish and skinless chicken were at a decreased risk.
In another study, the EPIC study, a database of over 470,000 men and women from 10 European countries was examined. Colorectal cancer was positively associated with a dietary high in red and processed meat, but inversely associated with a diet high in fish.
A review of 13 published studies found a significant association with a diet in meat and the risk of colon cancer. The study found that for each 100 grams of meat eaten each day there was a 12-17% increase in the risk of colon cancer.
A recent study published in The Journal of Nutrition attempts to answer why African Americans get more colon cancer than native Africans. They examined the diets of a number of African Americans as compared to native Africans. They also examined the intestinal bacteria of the study participants as there is evidence that a diet high in meat inhibits beneficial bacteria and promotes detrimental bacteria. Hydrogen-producing bacteria harm the digestive lining, or mucosa, while methane-producing bacteria protect the mucosa by detoxifying the hydrogen into methane.
They found that African Americans consume more protein, fat, animal protein, and cholesterol that native Africans. They also found that African Americans have a higher amount of the damaging hydrogen-producing bacteria and a lower amount of the beneficial methane-producing bacteria than their studied native African counterparts. “Our results suggest that the significantly higher intakes of animal protein and fat and the higher colonic colonization with hydrogen-producing bacteria and lower activity of colonic mathanogenic (methane producing) bacteria help explain the higher risk of colon cancer in African Americans.”
The researchers also examined the colons of native Africans versus African Americans. They found that the colons of native Africans were “far healthier” than those of matched Americans. Epithelial cell proliferation is a marker for cancer risk and the researchers found that rate to be more than 10 times greater in African Americans which the researchers found “particularly striking”.
The authors conclude that the risk of colon cancer is determined by an overall lifetime of environmental factors some of which promote intestinal health and some of which are detrimental for intestinal health. “Our study confirms the USDA [United States Department of Agriculture] figures that suggest Americans, and particularly African Americans, consume excess quantities of animal protein and fat and lead us to the conclusion that a healthier lifestyle that includes less meat and more fruit, vegetables, grains, and exercise should be beneficial not only for the colon but also for general health.”
Source: The Journal of Nutrition, January 2007
Author: Roman Bystrianyk