When talking to patients about reducing their cancer risks, nearly every one asks me about diet and nutrition. For people worried about colon cancer, breast cancer, and especially prostate cancer, I advise them to curtail or eliminate the consumption of red meat. While I focus on colon cancer below, very strong epidemiologic data also exist for breast and prostate cancers. In fact, information from national statistical databases have illustrative data that links the per capita animal fat consumption, such as that derived from red meat products, with a linear relationship to the development of these three common types of cancer.
Red meat and colon cancer
Diet has a powerful influence on many diseases, including America's number two killer, cancer. But because cancer is so complex, with many genetic and environmental factors affecting risk, the link between your menu and your risk has been hard to decipher. In the case of red meat and colon cancer, however, new research provides a plausible explanation for a long-suspected association.
Establishing a link
Although the results vary, studies from around the world have suggested that a high consumption of meat is linked to an increased risk of colon cancer. In some studies, fresh meat appears culpable; in others, it's processed, cured, or salted meat - but in all cases the worry is confined to red meat, not chicken. A meta-analysis of 29 studies of meat consumption and colon cancer concluded that a high consumption of red meat increases risk by 28%, and a high consumption of processed meat increases risk by 20%.
Scientists have offered a number of explanations for the link between red meat and colon cancer, and a study from England offers a new explanation. The investigation recruited healthy volunteers who agreed to stay in a metabolic research unit where their diet could be carefully controlled and all of their fecal waste could be collected and analyzed. The volunteers ate one of three test diets for a period of 15 to 21 days. The first diet contained about 14 ounces of red meat a day, always prepared to minimize HCA (need to spell out this abbreviation afater initial use) formation. The second diet was strictly vegetarian, and the third contained large amounts of both red meat and dietary fiber.
Stool specimens from the 21 volunteers who consumed the high-meat diet contained high levels of N-nitroso compounds (NOCs), which are potentially cancer-causing chemicals. The 12 volunteers who ate vegetarian food excreted low levels of NOCs, and the 13 who ate meat and high-fiber diets produced intermediate amounts.
These results are interesting enough on their own, but the researchers went one step further. They were able to retrieve cells from the lining of the colon that are shed into the stool with every bowel movement as a normal event. The cells from people eating the high-meat diet contained a large number of cells that had NOC-induced DNA changes; the stools of vegetarians had the lowest number of cells with damaged genetic material, and the people who ate high-meat, high-fiber diets produced intermediate numbers of damaged cells.
What you can do
The study from England showed that large amounts of red meat can produce genetic damage to colon cells in just a few weeks. It's an important finding, but it does not prove that red meat causes cancer. None of the cells were malignant, and the body has a series of mechanisms to repair damaged DNA. In most cases, the repairs are successful, but when they fail, cells can undergo malignant transformation.
Still, the research fits with earlier epidemiologic data raising a red flag about red meat. Instead of counting on your body to repair your damaged DNA, do everything you can to prevent damage in the first place.
In the case of colon cancer, there is quite a lot you can do:
- Keep your caloric intake reasonable and exercise regularly. Both of these choices appear to lower substantially the risk of colon cancer, and together they prevent obesity, a major cancer risk factor.
- Avoid tobacco in all its forms
- If you choose to drink, limit yourself to an average of no more than one or two drinks a day.
- Eat foods that have been associated with protection from colon cancer: a dietary pattern that includes good amounts of calcium from dairy products (low- or nonfat, please); vitamin D; fruits; vegetables; whole grains; and fish appear best. And yes, that dietary pattern eschews large amounts of red meat and other animal fats.
- Low-dose aspirin may also reduce risk.
- Be sure to get the colon cancer screening tests that are appropriate for your age, family history, and risk factors.
So my advice to those seeking dietary and nutritional info-save your money and don't buy expensive vitamins and minerals. Instead, decrease or eliminate red meat from your diet - sound advice backed by increasingly credible scientific information.
What do you do to lower your cancer risk? Have you stopped eating red meat, or cut back on it?Â
Marc Garnick, M.D., is an internationally renowned expert in medical oncology and urologic cancer, with a special emphasis on prostate cancer. He is a Clinical Professor of Medicine at Harvard Medical School and maintains an active oncology practice at Beth Israel Deaconess Medical Center. Dr. Garnick serves as Editor in Chief of Perspectives on Prostate Diseases, a quarterly report from Harvard Health Publications.
Colorectal cancer is the third most common form of cancer in men and women. Harvard Medical School's special report, Preventing and Treating Colorectal Cancer, details the latest research in both prevention and treatment of the disease, including screening tests, chemotherapies, and lifestyle recommendations like diet and physical activity. Learn who is at risk, what options are available for treatment, and what is on the horizon for colorectal cancer research.
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