Colon cancer is the fourth most common cause of death from cancer worldwide, killing more than 600,000 people each year. Many studies show that diets low in fiber and high in red meat are associated with increased risk for colon cancer. Now a new study shows that after just two weeks on a diet restricting red meat and adding lots of fruits, vegetables, beans and seeds, African-Americans had a significant reduction in specific colon bacteria and other risk factors for colon cancer (Nature Communications, April 28, 2015).
The rate of colon cancer in African-Americans is 13 times higher than in genetically similar rural Africans. African-Americans eat far more animal protein, fried foods and fat, and far less fibrous foods and produce far more carcinogenic bile acids and markers of precancerous colon changes and far less cancer-preventing short-chain fatty acids. After two weeks on the study diet, the African-Americans had increased levels of the bacteria that help prevent colon cancer (saccharolytic fermentation and butyrogenesis) and higher levels of short-chain fatty acids that help prevent colon cancer and far lower levels of bile acids that cause colon cancer. Going in the other direction, after just two weeks on a diet full of hamburgers and French fries, the rural Africans had an increase in bacteria and bile associated with increased risk for colon cancer. At the start of the study, almost half of the African-Americans and none of the Africans, had pre-malignant polyps in their colons.
Another study showed a dramatic increase in colon cancer after one generation of eating a high meat and low plant diet. Rural Japanese have an extremely low incidence of colon cancer. However, after moving to Hawaii and eating the American diet of hamburgers and French fries, their children developed a very high rate of colon cancer (Ethn Dis, 2004 Summer;14(3):431-9).
How Plants Help Prevent Colon Cancer Fruits, vegetables and whole grains are full of soluble fiber which cannot be absorbed in the stomach or intestines. When the soluble fiber reaches the colon, certain bacteria there ferment it to form short chain fatty acids that help prevent colon cancer. The process also lowers blood cholesterol levels to help prevent heart attacks. Since bacteria in the colon eat the same things that you do, providing your colon with soluble fiber causes the bacteria that “eat” soluble fiber to grow luxuriously there. These bacteria convert soluble fiber to cancer-preventing butyrate, so eating high-fiber foods markedly increases the production of butyrate in the colon.
How Red Meat and Processed Meats Can Increase Colon Cancer Risk Heme Iron: Red meat is red because it is full of heme-iron that makes our blood red. Heme-iron is broken down in our intestines to form chemicals called N-nitroso compounds that have been shown to cause cancer in animals. Plants may help prevent colon cancer because they contain chlorophyll, the green pigment in plants, that blocks the breakdown of heme and absorption of iron in the intestines. Heterocyclic amines (HCAs): When meat is cooked at high temperatures, the sugar in meat binds to protein to form heterocyclic amines that are known to cause cancers in animals. Nitrosamines: Processed meats have nitrates added to help keep them fresh longer. Nitrates are converted into nitrosamines both in the meat and in the human body, and nitrosamines are known to cause cancer in animals.
My Recommendations Everybody should eat lots of fruits, vegetables, beans, nuts and seeds, regardless of what else you do in your diet. The evidence associating red meat with colon cancer is so strong that I believe you should avoid red meat.
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