Too Much Fish Oil Might Boost Prostate Cancer Risk
Often-fatal aggressive disease of particular concern
Based on these and other findings, Brasky thinks men should probably moderate their intake of fatty fish and fish oil supplements.
"We are getting to the point where we don't see a lot of benefit for heart disease. Some of the enthusiasm for these fats has been premature," he added.
One expert cautions that these new findings don't show a cause-and-effect relationship between prostate cancer and omega-3 fatty acids.
"All of these studies on associations, which is what this is, are hypothesis-generating because they are looking back in time," said Dr. Anthony D'Amico, chief of radiation oncology at Brigham and Women's Hospital in Boston. "It's not a cause and effect."
The study would have to account for other risk factors for prostate cancer before it could be considered definitive, he said. These include family history, age and race, among others, D'Amico explained.
For the study, researchers used data from the Selenium and Vitamin E Cancer Prevention Trial, which found no benefit from either of these nutrients but an increase for prostate cancer for vitamin E.
The researchers compared blood levels of omega-3 fatty acids in more than 800 men later diagnosed with prostate cancer with blood samples from nearly 1,400 men who did not develop the disease.
The difference in blood levels of omega-3 fatty acids between the lowest- and highest-risk groups was about 2.5 percent (3.2 percent versus 5.7 percent) -- a gap larger than achieved by eating salmon twice a week, the researchers noted.
The investigators found that men eating the most fatty fish and taking the most fish oil supplements had an overall 43 percent increase in risk for all prostate cancer, compared with men eating the least fish or taking the fewest supplements. The risk for aggressive prostate cancer was 71 percent higher; for non-aggressive prostate cancer, the risk was 44 percent greater.