US scientists said Wednesday they have confirmed a surprising 2011 study that found a higher risk of prostate cancer among men who consume omega-3 fatty acids, raising new questions about the safety of supplements.

The research in the Journal of the National Cancer Institute reported a 71 percent higher risk for dangerous high-grade prostate cancer among men who ate fatty fish or took fish-oil supplements, which are often touted for their anti-inflammatory properties.

‘We’ve shown once again that use of nutritional supplements may be harmful,’ said Alan Kristal, researcher at the Fred Hutchinson Cancer Research Center and senior author of the paper.

Scientists are still puzzled as to why omega-3s appear linked to a greater risk of prostate cancer, but they said the findings suggest they are somehow involved in the formation of tumors.

The same team of researchers published similar findings in 2011, linking high blood concentrations of DHA to a more than double risk of high-grade prostate cancer, which is more likely to be fatal than other types.

A large European study also found the same omega-3 and prostate cancer link.

‘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 […]