Prostate cancer is the most common cancer, other than skin cancers, in American men, according to the American Cancer Society (ACS). ACS estimates that 192,280 new cases of prostate cancer will be diagnosed in the United States in 2009.

What men eat strongly influences prostate cancer risk, and consuming dairy products can contribute to an increased risk of this disease.

Men who consume low-fat and nonfat milk face an increased risk of prostate cancer, according to two studies in the American Journal of Epidemiology. One study included 82,483 men in the Multiethnic Cohort Study, 4,404 of whom developed prostate cancer over an average follow-up of eight years. Researchers found no association between prostate cancer risk and calcium and vitamin D intake, whether in the form of food or supplements. But the study did find a positive association between consuming 1 cup or more per day of low-fat or nonfat milk and developing prostate cancer.

The other study included 293,888 participants in the National Institutes of Health (NIH)-AARP Diet and Health Study. Consuming two or more daily servings of skim milk was associated with an increased risk of advanced prostate cancer.

Several previous studies—including two large Harvard studies—have shown that milk-drinking men have a significantly higher risk of prostate cancer. Researchers offer two possible reasons for the association: Milk drinking increases blood levels of insulin-like growth factor, which is associated with cancer risk. It also decreases activation of vitamin D precursors. Vitamin D helps protect the prostate against cancer.

Men who have prostate cancer can increase their chances of survival by following a low-fat vegan diet. By increasing consumption of cancer-fighting vegetarian foods and avoiding foods that feed tumor growth, such as dairy products and meat, men may significantly increase chances of living longer after prostate cancer diagnosis, according to a review in Nutrition Reviews in 2007.

Researchers found that low-fiber diets raise circulating testosterone, estradiol, and insulin levels, which in turn may fuel prostate cancer cell growth. Among men with the highest intake of saturated fat, the risk of dying from prostate cancer is three times higher than among men with the lowest intake.

Men with prostate cancer who follow a low-fat vegetarian diet benefit from increased quality of life and slowed PSA doubling time, according to a study in Urology. PSA doubling time is the amount of time it takes for levels of prostate-specific antigen, a biological marker for prostate cancer, to increase by 100 percent.

The study, led by Dean Ornish, M.D., focused on 36 men who had been diagnosed with prostate cancer, had undergone primary treatment for more than six months, and had continuous increases in PSA levels. The men were assigned to attend vegetarian nutrition and cooking classes or to a control group. Those in the vegetarian intervention group consumed significantly less saturated fat, more vegetable protein, and less animal protein, including fewer dairy products. The mean PSA doubling time at the three-month follow-up was substantially longer for the intervention group compared with that of the control group, meaning that the diet slowed cancer growth.

Men who want to avoid prostate cancer should follow a low-fat vegetarian diet. Which foods should men focus on? Building a balanced diet from whole grains, beans, fruits, and vegetables is the best way to go. But a few foods stand out as powerful fighters in the battle against prostate cancer.

Black, pinto, small red, and kidney beans are high in fiber, which helps the body rid itself of excess testosterone, and are among the 20 most antioxidant-rich foods. Beans are also rich in inositol pentakisphosphate, a known cancer-fighter.

Tomatoes and other lycopene-rich foods, such as watermelon and pink grapefruit, are associated with a reduced risk of prostate and other cancers. Studies from the Harvard School of Public Health have shown that men who frequently consume lycopene-rich foods cut their prostate cancer risk by one-third.

Broccoli and other cruciferous vegetables, including kale and cauliflower, are rich in sulforaphane, a cancer-fighting phytochemical that helps rid the body of excess testosterone and reduces the risk of prostate and other cancers.

Soy, nut, and rice milks are a healthy alternative to cow’s milk, which is known to increase the risk of prostate cancer. According to two major Harvard studies, men who avoided dairy products cut their prostate cancer risk by as much as 25 to 40 percent. Soy foods are also associated with a lower risk of cancer. Excellent plant sources of calcium are broccoli, brussels sprouts, kale, mustard greens, and fortified products such as orange juice and soymilk, and these foods will also provide your body with important cancer-fighting nutrients.

Need more information on prostate cancer and or making the transition to a vegetarian diet? Visit www.CancerProject.org for delicious recipes, information on nutrition and cooking classes, fact sheets on nutrition and cancer, DVDs, videos, books, and a free copy of The Cancer Project’s booklet Healthy Eating for Life: Food Choices for Cancer Prevention and Survival.

By Jennifer K. Reilly, R.D. The Cancer Project