Give a man a fish and you’ll feed him for a day, teach him how to fish and you could increase his risk of prostate cancer.

Men should be wary of taking omega-3 fatty acid supplements now that new research from the National Cancer Institute links them to an increased risk of prostate cancer.

A new study published yesterday in the Journal of the National Cancer Institute provides further evidence that men with high concentrations of omega-3 fatty acids in their blood are more likely to develop prostate cancer, the most common cancer affecting men.

The study clarifies previous research that was inconsistent about the link between omega-3 fatty acids and prostate cancer.

Omega-3 fatty acids are common in fish like salmon, flaxseed oil, nuts, and certain spices. Numerous studies have found that they can be good for a person’s heart and can help lower cholesterol.

Due to its positive health effects, fish oil supplements high in omega-3 fatty acids have become one of the most common supplement types on the market.

The research team, consisting of experts at leading institutions across America, studied 834 men diagnosed with prostate cancer. Of them, 156 had high-grade cancer.

Researchers found that men with the highest concentrations of fish-derived omega-3 fatty acids in their blood had a 43 percent greater risk of developing the cancer compared to men with the lowest concentrations.

On the flip side, they found that men with higher concentrations of linoleic acid, an omega-6 fatty acid, had lower incidences of prostate cancer. Linoleic acid is found in high concentrations in salicornia, safflower, sunflower, poppy seed, grape seed, and evening primrose oils.

It’s also found in olive oil, which is similarly high in omega-3 fatty acids.

With the new study in hand, researchers say doctors should weigh a man’s prostate cancer risk before recommending omega-3 fatty acids in foods or supplements.