Omega-3 Fatty Acids (Fish Oil) Linked To Prostate Cancer

That's what this study found:

Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial, Journal of the National Cancer Institute, 10 July 2013

This was a large case-cohort study. Cases were 834 men with prostate cancer, of which 156 had high-grade cancer. Researchers found a significant increase in prostate cancer risk among men with high concentrations of omega-3s (EPA, DPA, DHA) in their blood. Those with the highest concentrations were 43% more likely to develop prostate cancer and 71% more likely to develop high-grade cancer compared to those with the lowest levels of omega-3s.

Conclusions:

"This study confirms previous reports of increased prostate cancer risk among men with high blood concentrations of LCω-3PUFA [omega-3]. The consistency of these findings suggests that these fatty acids are involved in prostate tumorigenesis. Recommendations to increase LCω-3PUFA intake should consider its potential risks."

This isn't the first time I visited this:
Omega-3 Fatty Acid DHA Found To Increase Risk For Prostate Cancer, April 2011

"Men with the highest levels of one type of omega-3 (docosahexaenoic acid (DHA), found abundantly in fish oil) were two and a half times more likely to have an aggressive form of prostate cancer than men with the lowest levels."

The Japanese in Okinawa in 1950, some of the longest lived people in the world, were consuming fish at about 1% of their total calories - half an ounce a day. That's about one 3-ounce serving of fish a week. Depending on the fish (e.g. catfish, tuna, mackerel), that's about 500 mg omega-3 a week or about 70 mg/day. So, a gram of fish oil a day is 15 times the amount older Okinawans ate.
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