Eating to Prevent Colorectal Cancer

Medically Reviewed by Jennifer Robinson, MD on August 11, 2022
4 min read

Proper nutrition and diet are important in helping to prevent many diseases, and colorectal cancer is no exception. In the fight against this disease, nutritional guidelines include eating less saturated fat and getting more nutrients from the food you eat rather than from supplements.

Dietary fat from red and processed meats may be contributors to the colorectal cancer-causing process. High fat consumption increases the amount of substances that are released into the digestive tract called bile acids. Bile acids help break down fats. When they get into the colon, the large amount of bile acids may be converted to secondary bile acids, which could promote tumor growth, especially of the cells that line the colon.

Another substance that is being studied to see where it fits in the fight against colorectal and other cancers is the antioxidant. Antioxidants work by bolstering the body's defenses against potentially dangerous substances called free radicals.

Free radicals are one of the by-products of oxygen use by every cell in our body. These substances damage the body's cells through oxidation, the same process that rusts metal and turns butter rancid. Oxidation has also been shown to contribute to heart disease, cataracts, aging, and infections.

The body's cells have a natural defense strategy against free radicals and are able to repair the damage caused by them. Antioxidants, such as selenium and beta-carotene, may help reinforce this protection. However, in clinical trials, neither of these agents has been shown to reduce cancer development. Studies have shown that antioxidants are best taken as foods as opposed to supplements. Some examples of antioxidants are carotene, beta-carotene, and lutein. Foods that are good sources of antioxidants include fruits, vegetables, and certain types of tea.

Folic Acid. Some studies suggest that folic acid may play a role in the fight against cancer while others show an increased risk for some types.  More studies are needed. It's already known to be essential in forming new cells and tissues as well as keeping red blood cells healthy. The most common sources of folic acid are citrus fruits and dark green leafy vegetables, especially spinach.

While there seems to be some potential benefit in consuming foods with folic acid as part of a regular healthy diet, studies do not show any anti-cancer benefit from taking folic acid supplements. In fact, some studies suggest that taking folic acid supplements may slightly increase the risk of cancer.

Calcium and Vitamin D. Recent studies have suggested that these two substances may not only strengthen bones, but may also help fight off colon cancer. Good sources of calcium include: milk, cheese, yogurt, salmon, sardines, and dark-green leafy vegetables such as kale, mustard, and collard greens. Sources of vitamin D include salmon, sardines, fortified cow's milk, egg yolks, and chicken livers -- and don't forget the sun. Twenty minutes of sun before 10 a.m. and after 3 p.m. is an excellent source of vitamin D.

Fiber has been thought to be a powerful weapon against cancer. Though there is conflicting research as to whether or not fiber has protective effects against colorectal cancer, there is evidence that fiber intake improves overall health. Good sources of fiber include: whole-grain cereals and breads, prunes, berries, kidney beans and other legumes, fresh fruits and vegetables, and brown rice.

Although it’s best to get the fiber you need from food, fiber supplements offer another source. Examples  include psyllium and methylcellulose. Anytime you increase your fiber intake, do it slowly to help prevent gas and cramping. It’s also important to drink enough liquids.

Recently discovered to be helpful in the fight against cancer, phytochemicals are non-nutrient substances such a flavonoids, polyphenols, and terpenes which are found in a variety of plant foods including tomatoes, citrus fruits, berries, peppers, carrots, broccoli, cabbage, and soybeans.

You can learn to eat a healthy, cancer-fighting diet by following these guidelines from the American Cancer Society:

  • Choose many of the foods you eat from plant sources.
  • Eat whole grains rather than refined whenever you can.
  • Limit your red and processed meats.
  • Be physically active; achieve and maintain a healthy weight.
  • Limit consumption of alcoholic beverages.