Study: Fish-oil supplements may cut breast-cancer risk

Fish-oil supplements may lower your risk of breast cancer, according to a newly published study, but don't run out and stock up on pills quite yet.

Researchers at the Fred Hutchinson Cancer Research Center surveyed more than 35,000 postmenopausal women in Western Washington and found that those who took omega-3 fish-oil supplements had a 32 percent lower incidence of breast cancer, but senior author Emily White doesn't recommend that women begin taking the highly touted capsules.

"The evidence is intriguing, but it's not definitive," said White, a University of Washington epidemiologist.

The survey-based study targeted people already taking supplements, which may introduce a bias.

"Supplement users may have healthier lifestyles," she said. "Or they may have other underlying health conditions."

To confirm the cancer-fighting benefits of fatty-acid supplements, researchers would need a rigorous and costly randomized clinical trial comparing fish-oil pills and placebos.

This would also reveal any potential side effects of taking omega-3 supplements, which contain five to 10 times more fatty acids than are naturally found in a serving of fish.

"When it comes to omega-3 fatty acids, we know that some intake is better than none for cardiovascular health," said cardiovascular-health specialist David Siscovick, an epidemiologist at the UW. "But it may not be that more is better. One to two servings of fish a week may be enough."

The American Heart Association recommends at least two servings of fish per week to enhance cardiovascular health but doesn't offer specific recommendations about supplements.

"Taking a supplement is not the same as eating a fish rich in fatty acid," said Siscovick, who dines on fish to get his omegas. "The fish might contain things other than omega-3s that contribute to heart health." Instead of supplements, he advocates making healthful diet choices.

Does that mean succumbing to the increasing array of omega-fortified food products on our grocery-store shelves?

Not necessarily, the researchers said. Just as with fish-oil pills, there's no conclusive evidence to support that fortified foods are more than a marketing campaign aimed at health-conscious buyers.

Flax seed and other vegetarian omega-rich sources may also confuse consumers. These foods contain a fatty acid referred to as ALA, which is structurally different from the long-chain fatty acids found in marine fishes, referred to as EPA and DHA.

These latter two omegas are key structural molecules in our heart and brain, according to Michael Brett, an aquatic biologist at the UW.

Getting the same health benefit from consuming vegetable sources such as flax seed would be almost impossible because our bodies can't utilize ALA efficiently, said Brett, who has his family on a daily regimen of fish-oil supplements.

Consumers might soon know if omega-3 fish-oil supplements offer the benefits their producers claim. Harvard University has initiated a federally funded randomized trial looking at their health benefits.

"The scientific evidence for fish oil is to the point where we should definitively test it," White said. But until she sees the results, she'll stick to getting her fatty acids from fish.

The Fred Hutchinson study was published in the July issue of the journal Cancer Epidemiology, Biomarkers & Prevention.

Cassandra Brooks: 206-464-2311 or cbrooks@seattletimes.com