Surprising findings on omega-3s, trans fats, and prostate cancer risk don’t warrant a change in diet

By Suzanne Rose, Editor, Annual Report on Prostate Diseases

Over the past four years, I’ve read numerous studies and spoken with several experts on the connection between nutrition and prostate cancer. Although their recommendations for men concerned about prostate health haven’t always been consistent, most agreed on two things: eat more healthy fat, particularly the omega-3 fats found in fatty fish like salmon, and eat less unhealthy fat, namely trans and saturated fats. So I did a double take when I came across a study in the American Journal of Epidemiology that came to the opposite conclusion.

Chronic inflammation may play a role in the development and progression of prostate cancer. Omega-3 fats tend to be calm inflammation, while trans fats tend promote it. So researchers analyzed data and blood samples from 3,461 men ages 55 to 84 in the nationwide Prostate Cancer Prevention Trial to examine the relationship between the levels of these and other fats and prostate cancer risk.

Men with the highest levels of DHA, a type of omega-3, were 2.5 times more likely to have developed aggressive, high-grade prostate cancer over a seven-year period compared with men who had the lowest levels of DHA—the exact opposite of what the researchers had hypothesized. Another surprising result was that men with the highest blood levels of trans fats, often found in processed foods, were 50% less likely to have developed aggressive, high-grade prostate cancer compared with those who had the lowest levels.

“Our findings are disconcerting,” the researchers wrote,” as they suggest that omega-3 fatty acids, considered beneficial for coronary artery disease prevention, may increase high-grade prostate cancer risk, whereas trans fatty acids, considered harmful, may reduce high-grade prostate cancer risk.”

Should these results prompt men to scale back on fish and eat more processed food? I put that question to Stacy Kennedy, senior clinical nutritionist at Dana-Farber Cancer Institute, and Dr. David Rosenthal, director of Harvard University Health Service and medical director of the Leonard P. Zakim Center for Integrative Therapies at Dana-Farber. Both gave me an emphatic “no.” One key reason: the risk of dying from heart disease is much higher than the risk of dying from prostate cancer.

Eating moderate amounts of wild salmon, walnuts, pumpkin seeds, and other foods rich in omega-3s is a healthy strategy, Kennedy told me. The best “medicine” for men who are worried about their risk of prostate cancer is to maintain a healthy weight, eat plenty of fruits and vegetables, exercise regularly, and control stress. The good news is that taking these steps will promote heart health, too.

Posted May 5, 2011