The benefits of omega-3s in fighting heart disease may be only so-so, according to a new review of research on the fatty acids found in fish and some plant and nut oils.

The study doesn't rule out an important effect of omega-3 fatty acids on health, but the results indicate that the evidence behind the fishy fats is less conclusive than previously thought.

Eating foods rich in omega-3 fatty acids, such as fatty fish and some plant and nut oils, such as olive and walnut, is thought to lower the risk of heart disease, and several public health organizations have recommended that people to eat more oily fish, such as salmon and tuna.

But in a review of 89 studies that measured the effect of omega-3 fatty acids on heart attack, death, cancer, and strokes, researchers didn't find any clear benefit of omega-3s in reducing the risk of these health hazards.

Omega-3's Health Benefits Questioned

In the review, which appears in the journal BMJ, researchers analyzed the results of studies that looked at the omega-3 fatty acids on reducing health risks in people who increased their intake of omega-3s through diet or supplementation with fish oil capsules for six months or more.

After taking differences in study quality into account, researchers found the pooled results of the studies showed no strong proof that omega-3 fatty acids had an effect on reducing the risk of death or heart-related events, like heart attack and stroke.

Researchers say other recent reviews of studies on omega-3s have shown that people taking supplements of the fatty acids had a lower risk of death, and they can't explain why this review came up with conflicting results.

Therefore, they recommend that further study is needed to fully understand the benefits and risks of omega-3 fatty acids.

In an editorial that accompanies the study, Eric Brunner of the department of epidemiology and public health at the Royal Free and University College London Medical School writes, "We are faced with a paradox.

"For the general public some omega-3 is good for health," writes Brunner. "Health recommendations advise increased consumption of oily fish and fish oils. However, industrial fishing has depleted the world's fish stocks by some 90% since 1950, and rising fish prices reduce affordability particularly for people with low incomes. Global production trends suggest that, although fish farming is expanding rapidly, we probably do not have a sustainable supply of long-chain omega-3 fats."