Omega-3 fatty acids offer no cancer protection

Eat your fatty fish and hang on, if you wish, to that bottle of tasty fish oil – but don’t expect them to protect you from cancer. A new study says that foods and supplements containing omega-3 fatty acids do not offer such protection, dashing some earlier hints that they might.

The analysis of 38 studies conducted between 1966 and 2005 suggests that omega-3s (which are found in many kinds of fish and some plant sources) have no significant effect on a variety of cancers, including those of the breast, colon, lung and prostate.

The report noted that a few studies with a small number of subjects appeared to show that omega-3 fatty acids offer some cancer protection. But most showed no relationship – and a few even showed an increased risk. The studies included more than 700,000 adults, tracked for up to 30 years.

“Omega-3 fatty acids aren’t a panacea,” says Dr. Catherine MacLean, lead author of the study and a researcher at the Rand Corp. in Santa Monica, Calif. “Although other research shows that (they) are good for your heart and your general health, the benefits don’t appear to extend to cancer.”

Fish sources rich in omega-3 fatty acids include salmon, mackerel, anchovies, herring and cod liver oil. Plant sources (of a slightly different omega-3 fatty acid) include flax seeds, canola oil, soybeans, wheat germ, peanut butter and walnuts.

The report, published last week in the Journal of the American Medical Association, is one of a series of investigations on omega-3 fatty acids sponsored by the U.S. government.