Senior author Alan Kristal, a member of the Fred Hutchinson Cancer Research Center's Public Health Sciences Division, said the latest findings indicate that high concentrations of EPA, DPA and DHA -- the three anti-inflammatory fatty acids from fatty fish and fish-oil supplements -- are associated with a 71 percent increased risk of high-grade prostate cancer.
The study, published in the online edition of the Journal of the National Cancer Institute, also found a 44 percent increase in the risk of low-grade prostate cancer and an overall 43 percent increase in risk for all prostate cancers.
A 2011 study published by the same Fred Hutchinson team reported a similar link between high blood concentrations of DHA and a more than doubling of the risk for developing high-grade prostate cancer. This latest study also confirms results from a large European study, Kristal said.
"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 risks," the study authors wrote in the paper.
Kristal said the findings in both studies were surprising because omega-3 fatty acids are believed to have a host of positive health effects based on their anti-inflammatory properties. Inflammation plays a role in the development and growth of many cancers, Kristal said.
It is unclear why high levels of omega-3 fatty acids would increase prostate cancer risk, but the replication of this finding in two large studies indicates the need for further research.