Can a Mediterranean diet prevent colon cancer?

Are all healthy eating plans the same when it comes to cancer prevention?

Researchers at the University of Michigan Comprehensive Cancer Center are beginning a study to look at whether diet can impact a person’s risk of developing colon cancer. Specifically, the researchers will compare a Mediterranean diet – high in olive oil, nuts and fish – with a standard healthy eating plan.

“Overall eating patterns appear to be more important for cancer prevention than intakes of specific nutrients or food groups. We hope this study will give us an indication of the benefits that a person’s diet can have on health, especially in terms of reducing the risk of colon cancer,” says Zora Djuric, Ph.D., research professor of family medicine at the U-M Medical School and principal investigator on the Healthy Eating for Colon Cancer Prevention study.

The study will look at adults age 21 or older who have had colon polyps, colon cancer or a family history of colon cancer. Researchers hope to recruit 120 participants over three years. Participants will be randomly assigned to follow either the Mediterranean diet or the Healthy People 2010 diet for six months. A dietitian will work closely with each participant by telephone. Participants can choose foods they prefer from recommended food group lists.

The Mediterranean diet focuses on vegetables, whole grains, fruits, fish and olive oil. High fat meats and processed foods are limited. The comparison diet is the Healthy People 2010 diet, which is the U.S. Department of Health and Human Services’ plan for healthy eating. The Healthy People 2010 diet involves eating plenty of fruits and vegetables, whole grains and a moderate fat intake with limits on saturated fat.

Study participants assigned to the Mediterranean diet will be encouraged to limit polyunsaturated fats from foods such as corn oil in favor of monounsaturated fats from olive oil, nuts and fatty plant-based foods such as olives. Mediterranean diet participants will also be expected to eat seven to nine servings of fruits and vegetables, including herbs, and get protein primarily from low-fat sources such as poultry, fish and legumes.

Previous studies have linked the Mediterranean diet to reduced risk of heart disease, stroke and cancer. Some evidence suggests the Mediterranean diet causes changes in the colon that would prevent cancer.

U-M researchers recently concluded a study of 70 women ages 25-65 who were randomly divided between following a Mediterranean diet or following their usual dietary habits. The researchers found the study participants were able to stick to the Mediterranean diet throughout the study. The women following a Mediterranean diet decreased the amount of polyunsaturated fat they ate by 50 percent while increasing the amount of healthy monounsaturated fats by the same amount. The women also ate twice as many fruits and vegetables as those following their regular diet. This doubled the blood levels of carotenoids, which are antioxidant micronutrients from fruits and vegetables.

Researchers believe changes in dietary fatty acids from the higher monounsaturated fat intake with a Mediterranean diet will decrease the levels of certain proteins in the body that are linked to the development of colon cancer. At the same time, other cancer-protective compounds are expected to increase because of the Mediterranean diet.