Colon cancer: Seven tips about what will and won't lower your risk

There are definitely recurring themes in cancer prevention, and the following tips are worth taking note of — and not only for colon cancer prevention. For example, I have been telling my prostate cancer patients for decades to avoid red meat, and the data on its role in colon cancer prevention back up this advice. And the many benefits of staying slender and being active are all the more compelling when the protection against colon cancer is factored in.

So here are some tips to decrease your colon cancer risk — and the risk of many other diseases. The only one that presents a real dilemma is the idea that high calcium intake may decrease colon cancer risk — because it also may increase prostate cancer risk. Read on for the bottom line on that quandary.

1. Cut back on the red and processed meat. The studies don't line up perfectly, but many point to increased colon cancer risk among people who eat a lot of red (beef, lamb, pork) and processed meat (bacon, ham, hot dogs, sausage, and so on). The risk from processed meat might be greater than it is from red meat. Why red meat might cause colon cancer is unclear. Some studies suggest that the heme iron it contains promotes cell division and cancerous growth. Chicken doesn't seem to increase colon cancer risk, and one study found it might even reduce the risk.

2. Stay active. Physical activity seems to protect against colon cancer. Some studies suggest that you'll get even more protection if you exercise vigorously. But Danish researchers reported in 2006 that activity level wasn't as important as the number of different activities people participate in.

3. Stay slender. Harvard studies identified a connection between obesity and colon cancer in 1995. Some nuances have emerged since. Obese men of all ages are at risk, but for women, premenopausal more than postmenopausal obesity is the danger. Being overweight (a BMI of 25 to 29.9) increases your risk, but only half as much as being obese (a BMI of 30 or higher). Visceral fat, which accumulates in the belly and clings to the abdominal organs, may pose more of a risk than fat under the skin that widens hips, thighs, and buttocks.

4. Adequate calcium intake is good enough for most. High milk and calcium consumption have been linked to lower colon cancer risk in epidemiologic studies. And one important trial showed that in people who'd already had a polyp removed, taking 3,000 mg of calcium carbonate daily (1,200 mg of elemental calcium) reduced the risk of recurrence by 20%. But when daily calcium (1,000 mg) and vitamin D (400 IU) supplements were tested in the landmark Women's Health Initiative study, they had no effect on colon cancer rates. Some research suggests that calcium is protective but that daily intake over 1,000 mg probably doesn't add much. Other data suggest that we've paid too much attention to calcium and that vitamin D is the real risk reducer. Men are expressly advised by the American Cancer Society not to get too much calcium (1,500 mg or more daily) because large amounts may increase prostate cancer risk. The bottom line: People who have had polyps should talk to their doctors about taking a calcium supplement. High levels of calcium intake have been shown to reduce the risk of getting more polyps. But others can get the calcium they need by eating a balanced diet.

5. Nothing special about fiber. Loading up on fiber was once thought to be our best defense against colon cancer. No more. In clinical trials, fiber hasn't worked to reduce recurrent polyps, and the epidemiological evidence that it protects against first-time polyps is uneven. (Diets high in fiber do seem to reduce the risk of heart disease and diabetes, however, so don't forget about it entirely). Whole grains are a great source of dietary fiber, but have other ingredients as well. Results from a National Institutes of Health–AARP study published in 2007 showed that whole-grain consumption, but not fiber specifically, was associated with a modest reduction in colon cancer risk.

6. Hormone therapy isn't worth the other risks. If colon cancer were the only health concern, many women might consider taking hormones to prevent it. In the Women's Health Initiative study, postmenopausal women who took an estrogen-progestin combination lowered their risk for colorectal cancer by 44%. But hormone therapy has other risks associated with it (including breast cancer and heart disease, depending on when it's taken relative to menopause), so it's not recommended for colon cancer prevention.

7. Get screened. The number of Americans dying each year from colon cancer has been declining. Treatment has improved, so people with the disease are living longer. But screening, so cancers are caught earlier, has played a role. The American Cancer Society recommends that people at average risk get their first screening test at age 50. Partly because it involves inspection of the entire colon, the colonoscopy has become increasingly popular.

Screening works because colon cancer is usually a slow-growing disease that starts with adenomatous polyps, small, protuberant growths inside the colon that may contain precancerous cells. Screening tests are designed to find these polyps so doctors can remove them before they become cancerous.

Colorectal Cancer
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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