Omega 3 rich oils fall from grace: May raise prostate cancer risk

By Dr. Ananya Mandal, MDApr 26 2011

The omega 3 fatty acids have enjoyed a pride of place among nutritional supplements for years now. The acid, technically known as docosahexaenoic acid (DHA), is found in certain oily fish like salmon, mackerel, tuna and trout. DHA has been known to reduce inflammation in the cardiovascular system, and many doctors and nutritionists recommend at least 450 milligrams a day as part of a healthy diet.

But a new study linked its use to an increased risk of fast-spreading prostate tumors. The team of researchers at the Fred Hutchinson Cancer Research Center in Seattle studied more than 3,400 men, half of whom had prostate cancer. The scientists were expecting that subjects who had a higher blood-concentration of DHA would tend to have a lower risk of prostate cancer, but they were wrong. Those men had 2.5 times the risk level. They also found that trans-fatty acids and omega-6 fats in vegetable oils - both of which increase inflammation -- actually decreased the risk of high-grade prostate tumors. The study notes that very few of the study participants got their DHA from supplements -- mostly from fish.

Theodore Brasky, who led the research that was published online Tuesday in the American Journal of Epidemiology said, “We were stunned to see these results and we spent a lot of time making sure the analyses were correct.” Brasky added, “Overall, the beneficial effects of eating fish to prevent heart disease outweigh any harm related to prostate cancer risk… What this study shows is the complexity of nutrition and its impact on disease risk, and that we should study such associations rigorously rather than make assumptions.”

According to Dr. Jack Jacoub, a medical oncologist at Orange Coast Memorial Medical Center in Fountain Valley there may indeed be a relationship between omega-3 and cancer, but unlike the positive association with cardiovascular risk, cancer is much harder to pin down. “There are so many variables that it’s almost impossible to control for everything,” he said “You have to take one study, especially when it comes to nutrition and its relationship to cancer, with a grain of salt because it could change a year from now.”