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Study: Omega-3 Won't Prevent Cancer

But They Still Pack Huge Health Benefits, Say Researchers
By
WebMD Health News
Reviewed by Louise Chang, MD

Jan. 24, 2006 -- Eating fish is good for you, but it won't prevent cancer, according to a new study.

It's no reason to stop eating fish rich in the important nutrients called omega-3 fatty acids. Omega-3 fatty acids cut your risk of heart disease and stroke and aid children's early mental development. They seem to do many other good things, too.

They just do not just fight cancer, find RAND researcher Catherine H. MacLean, MD, PhD, and colleagues. As part of a huge, government-funded study, MacLean's team looked for every scrap of evidence on omega-3 fatty acids and cancer risk. They analyzed 38 large studies that evaluated the risk of 11 different cancers in people who consumed different amounts of omega-3 fatty acids.

"Overall these studies -- ranging from 6,000 to 121,000 people, with 3 million person-years of observation, with people from a number of different populations, in a number of different countries -- we see a consistent finding," MacLean tells WebMD. "Over and over again we see that omega-3 fatty acids don't appear to reduce a person's risk of developing cancer."

The findings appear in the Jan. 25 issue of The Journal of the American Medical Association.

Omega-3 Fats Still Recommended

Nutritionist Leslie Bonci, MPH, RD, director of sports nutrition at the University of Pittsburgh and team nutritionist for the Pittsburgh Steelers, still recommends a diet that gives you plenty of omega-3 fatty acids. She isn't a bit deterred by the finding that the nutrient doesn't prevent cancer.

"It's still important to have omega-3 fatty acids in the diet," Bonci tells WebMD. "For heart disease, the benefit is clear. We know it cuts down on the amount of fat in the blood and reduces risk of stroke. That is very powerful information."

Omega-3 fatty acids are a type of unsaturated fat. People who eat plenty of these healthy fats are significantly less likely to get -- or to die from -- heart disease. Evidence behind this benefit came from an earlier study sponsored by the U.S. Agency for Healthcare Research and Quality (AHRQ), which also sponsored the MacLean study.

"We did find a positive relationship with omega-3 fatty acids and protection against heart disease," AHRQ Director Carolyn M. Clancy, MD, tells WebMD. "The findings are not specific enough to say if you eat salmon once a week and tuna twice a week you are OK. But it can help with heart disease -- and there is no strong evidence of harm."

Omega-3 Evidence Unclear

It's not clear why omega-3 fatty acids have this effect. One reason may be that they keep blood vessels from getting inflamed. Inflamed blood vessels tend to become clogged, leading to heart disease and stroke. But heart patients aren't the only ones who might benefit from omega-3 fatty acids.

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