Heart, yes; cancer, no

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. “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 Assn., is one of a series of investigations on omega-3 fatty acids sponsored by the U.S. government.