Omega-3 Linked to Increased Risk of Aggressive Prostate Cancer

SEATTLEConcentrations of eicosapentaenoic acid (EPA), docosapentaenoic acid  (DPA) and docosahexaenoic acid (DHA) are associated with a 71% increased risk of high-grade prostate cancer, according to a study published in the Journal of the National Cancer Institute.

This second large prospective study from Fred Hutchinson Cancer Research Center also found a 44% increase in the risk of low-grade prostate cancer and an overall 43% increase in risk for all prostate cancers.

High-grade prostate cancer risk is important in the study because the tumors are more likely to be fatal.

The study analyzed 834 men who had been diagnosed with primary prostate cancers156 with high-grade canceralong with a comparison group of 1,393 men selected randomly from 35,500 participants of the Selenium and Vitamin E Cancer Prevention Trial (SELECT).

A previous study published by the same team reported a similar link between high blood concentration of DHA and a more than double risk of developing prostate cancer.

"The consistency of these findings suggests that these fatty acids are involved in prostate tumorigenesis and recommendations to increase long-chain omega-3 fatty acid intake, in particular through supplementation, should consider its potential risk," the authors wrote.  Weve shown once again that use of nutritional supplements may be harmful," said Alan Kristal, Dr.P.H., the papers senior author and member of the Fred Hutch Public Health Sciences Division.

A replication of the finings from 2011 has confirmed that marine omega-3 fatty acids play a role in prostate cancer occurrence.

Another recent study questioned the benefits of omega-3 supplementation for cardiovascular disease with results showing that the supplementation does not appear to reduce the risk of cardiovascular disease, or strokes.  

 Its important to note, however, that these results do not address the question of whether omega-3s play a detrimental role in prostate cancer prognosis," said corresponding author Theodore Brasky, Ph.D., a research assistant professor at The Ohio State University Comprehensive Cancer Center.

The results were surprising because omega-3 fatty acids are believed to have a host of positive health effects based on their anti-inflammatory properties, Kristal said.

Further research is required since it is unclear why levels of omega-3 would increase prostate cancer.

One potentially harmful effect of omega-3 fatty acids is their conversion into compounds that can cause damage to cells and DNA, and their role in immunosuppression. Whether these effects impact cancer risk is not known.

The difference in blood concentrations of omega-3 fatty acids between the lowest and highest risk groups was about 2.5 percentage points (3.2 percent vs. 5.7 percent), which is somewhat larger than the effect of eating salmon twice a week, Kristal said.