Everyone knows that fish oil is good for you, right? It's a rich source of omega-3 fatty acids, which are marketed to reduce the risk of just about everything from heart disease to Alzheimer's.
But a startling study shows men who have the highest levels of these compounds—the kinds found in fish but not in vegetable sources—have a higher risk of prostate cancer. Men with the very highest levels had a 71 percent higher risk of high-grade prostate cancer—the kind most likely to spread and kill, they report in the Journal of the National Cancer Institute.
It might be a sign that popping a pill is not only possibly a waste of money—it might be downright dangerous. And eating fish too often might be, also.
"These fish oil supplements in which some men are getting mega, mega doses … in our opinion that is probably a little bit dangerous," said Theodore Brasky of Ohio State University Medical Center, who worked on the study with a team from the Fred Hutchinson Cancer Research Center in Seattle.
The same team published a study in 2011 that showed men with the highest levels of one omega-3 fatty acid called docosahexaenoic acid, DHA for short, had double the risk of high-grade prostate cancer. Other studies have had similar findings.