Alexander C. Chester, MD

Fish Oil and Prostate Cancer

A recent report in the Journal of the National Cancer institute concluded that men with a high blood concentration of fatty acids (omega-3) had an increased prostate cancer risk. The conclusion is concerning since it appears to contradict the assumption that fish oil and fatty fish consumption improve the overall health of men.

Moreover, the authors had previously found that high concentrations of trans-fatty acids (yes, the ones now restricted in food processing because of a clear association with heart disease) were associated with a decreased risk of aggressive prostate cancer. Trans-fatty acids are found in margarine and frying oils. Omega-6 fatty acids were associated with a lower risk of total prostate cancer.

Other studies have shown numerous health benefits of omega-3 fatty acid. One study showed a two- to three-fold greater risk for prostate cancer in men who ate no fish compared with those who consumed large amounts of fish in their diet. Other studies have also shown a decreased risk of prostate cancer and of metastatic prostate cancer in men who eat fish more than three times a week.

There are a number of problems with the recent study associating omega-3 fatty acid concentration with prostate cancer. We don’t know the source of the fatty acids in the study patients; there was no information on dietary habits or supplements taken. We don’t know anything about the subject’s risk factors for prostate cancer such as ethnicity, PSA levels, age and weight. Additionally, the study was based on a single blood test, not an analysis of concentrations over time.

Of interest, Japanese men consume the most omega-3 fatty acids from their diet in the world and yet are experiencing a declining risk for death due to prostate cancer. Additionally, many studies have demonstrated the cardiovascular benefits of omega-3 fatty acids.

Until more information is available to the contrary, in my opinion, it is prudent for patients with cardiovascular disease to consume oil fish several times a week and use fish oil if a dietary source is unavailable or unappealing.

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