Colon Cancer Update

(Berkeley Wellness) 

Colon Cancer: The Diet Connection

By far the most important way to prevent colon cancer is to get screened. The next most important step is to not smoke. Can diet help, too?

Colon cancer usually begins with polyps, small benign growths in the inner wall of the colon. Age is a risk factor; environmental factors­—particularly smoking—also play a role. People with chronic inflammatory bowel disease are at higher risk, as are those with a family history of colon cancer. The role of diet is less clear, but here’s the latest thinking.
What You Eat
• A diet rich in fruits, whole grains, and vegetables appears to lower the risk of many cancers, including colon cancer. Broccoli, cabbage, cauliflower, kale, and other members of the cruciferous family may, in particular, help prevent colon cancer due to their sulfur-containing compounds, called glucosinolates.
• Fiber, however, is no longer deemed important in preventing colon cancer. A high-fiber diet helps prevent constipation, and the theory was that this might reduce exposure of the intestinal wall to carcinogens. But several large studies have failed to find a protective effect. And there’s no known link between constipation and colon cancer. Fiber is hard to study—it isn’t just one compound but many.
• A high-fat diet, particularly one high in animal fats and red meats, has been blamed for increasing colon cancer risk, but the jury is still out. Dietary fat, in itself, is no longer regarded as a factor in colon cancer. If red meats do increase the risk—and some evidence suggests they do—it may be because they are often cooked at high temperatures, so that potential cancer-promoting chemicals are formed.
• Calcium and vitamin D may reduce the risk of colon cancer, whether you get these nutrients from food or supplements. In a 2008 review article, a high intake of dairy products, especially milk, was associated with a reduced risk of colon cancer, perhaps because of their calcium, vitamin D, and other nutrients. And a 2009 study suggested that the combination of daily calcium and vitamin D may help normalize growth of colon cells in people with a history of colorectal adenomas.
• Omega-3 fats from fish may reduce the risk of colon cancer, though the evidence is preliminary. In an analysis of data from the Physicians’ Health Study, those who ate the most fish were nearly 40% less likely to develop colon or rectal cancer over 22 years than those who ate fish less than once a week. Omega-3 fats in fish may reduce the chronic inflammation that has been implicated in colorectal cancer.
• Folate, a B vitamin, may also reduce the risk of colon cancer. But research is mixed, and some studies have suggested that 1,000 micrograms of folic acid (the form used in supplements) may actually increase polyp growth. A more recent Harvard study, however, found that this same high dose did not prevent or promote the growth of polyps in people prone to them; in fact, people with initially low blood levels of folate seemed to benefit. To be safe, you should avoid high intakes of folic acid from supplements and fortified foods.
• If you drink alcohol, keep your intake moderate—no more than two drinks a day for men, one for women. There may be a link between high alcohol intake and colon cancer.