Fish Oil Study: Higher Level of Omega-3 Fatty Acids May Lead to Increased Risk of Prostate Cancer

Millions of American men take fish oil supplements in an attempt to cut their risk of heart disease, but they might be increasing their chances of other ailments in the process.

According to a new study released Thursday in the Journal of the National Cancer Institute, men who have higher levels of omega-3 fatty acids in their system face a 43 percent increased risk of developing prostate cancer and a 71 percent increased risk of developing the high-grade form of the disease, which is most likely to spread and kill.

Researchers used data from a past study that looked at the blood concentrations of omega-3 polyunsaturated fatty acids in 834 men with prostate cancer and 1,393 men without prostate cancer. They found an association between the concentration of omega-3 levels and the incidence of prostate cancer.

"Men will probably want to talk to their doctors, especially those patients who have been recommended increased fish oil intake," lead study author Dr. Theodore Brasky of Ohio State University Comprehensive Cancer Center said. "They should probably moderate their intake of fatty fish and they should avoid fish oil supplements at this time, especially considering that when men are taking fish oil supplementation they are taking [higher doses than they need]."

Researchers found that fatty acids in vegetable oils, flaxseeds and other vegetable sources did not affect prostate cancer risk.

However, Brasky said the study does not answer the question of how exactly fish oil can cause cancer. And while The American Heart Association recommends people with heart disease eat fish twice a week and may need fish oil capsules, a study published in the New England Journal of Medicine in May concluded that taking extra omega-3 has little effect on heart disease.