Environmental Nutrition

About 50 percent of colorectal cancer, the third most common cancer among men and women in the U.S., can be prevented through daily diet, physical activity and weight management, making it one of our most preventable cancers.

Five specific steps toward that goal come from an evidence-based report on reducing risk of colorectal cancer released by the American Institute for Cancer Research (AICR) and World Cancer Research Fund (WCRF) as part of their Continuous Update Project (CUP). Here are those strategies, as well as some steps likely to offer additional protection:

1. Fill up on foods with fiber.

Each 10 grams of dietary fiber is linked with a 10 percent lower risk of colorectal cancer, according to an analysis detailed in the November 10, 2011 British Medical Journal. Whole grains stand out as particularly linked to lower risk. Fiber adds bulk and reduces the time your digestive tract is exposed to carcinogens. Also, high-fiber diets encourage growth of health-promoting types of bacteria -- trillions of which live in your gut.

--Focus on whole plant foods -- vegetables, fruits, whole grains, beans and nuts -- in order to reach levels of fiber linked with lowest risk. Whole plant foods, which provide fiber along with protective nutrients and phytochemicals, are best. Although you can get some of these benefits from fiber supplements or refined grains with added fiber, whole plant foods provide fiber along with protective nutrients and phytochemicals.

--Add beans or tofu to soups, stews and stir-fries.

--Start eating whole grain bread and pasta, then expand to a variety of unprocessed, cooked grains such as bulgur, whole wheat couscous, quinoa, and whole-grain polenta.

--Add some nuts or seeds (including ground flaxseed) to your morning cereal or smoothie.

2. Cut calories if you're carrying extra weight, especially if it's around your waist. Excess body fat secretes inflammation-inducing proteins and creates cancer-promoting changes in hormones like insulin and growth factors. Each one-unit increase in body mass index (BMI), which corresponds to five to seven pounds for most adults, is linked with a 2 percent increase in colorectal cancer risk. Fat deep in the abdomen poses the most risk. Each one-inch increase in waist links to a 5 percent increase in colon cancer risk. The key: don't simply add healthy foods; swap them for less healthy foods to boost nutrition and keep calories the same or lower.

--Sip water, seltzer, tea or coffee instead of soda or sugary tea and coffee specialty drinks.

--If you're not hungry, relax with a walk, meditation, music or a book instead of food.

3. If you drink alcohol, limit it to no more than one (for women) or two (for men) drinks a day.

Alcohol is metabolized to compounds that damage cells and can lead to cancer. Based on similar alcohol content, one standard drink is considered 12 ounces beer, 5 ounces of wine, 1.5 ounces of 80-proof liquor or 1 ounce of 100-proof liquor. For each one standard drink consumed daily, colorectal cancer risk increases 14 percent, according to analysis of multiple studies. Cancer risk is linked with alcohol content, not choice of beverage.

--Watch your glass size. With today's larger glasses, what you may consider one drink may be more.

--Choose seltzer flavored with fruit essence, or add slices of fruit to club soda, for a more enticing option than plain water.

4. Limit red meat (beef, lamb and pork) and avoid processed meat.

Each 3.5-ounce portion of red meat eaten daily increases colorectal cancer risk 17 percent, according to CUP analysis published in PLoS ONE in June 2011. Processed meat is even more strongly linked with risk; each portion half that size eaten daily increases risk 18 percent. Recommendations include limiting red meat, even if lean, to no more than 18 ounces a week and to save processed meat for occasional consumption. By swapping a couple of fish or seafood meals per week for red meat, you reduce colon cancer risk while promoting overall health.

Add a few more meatless meals to your week, making sure to include beans, lentils or some other source of protein.