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By the way, doctor: How much fish oil should I be taking?

By the way, doctor

How much fish oil should I be taking?

Q. What's the right daily dose of omega-3s? I have a bottle of 1,000-mg fish-oil pills. Is one a day enough to get the benefit?

A. The two main omega-3 fats found in fish are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Omega-3 fats, and perhaps especially EPA and DHA, have a variety of health benefits, but many people don't like the taste of fish or worry that it may contain toxins such as mercury. Fish-oil capsules are a way to get omega-3 fatty acids without having to eat fish. The capsules, while large and a bit hard to swallow, keep the fish oil well contained so you don't have to taste it, although some people still notice a fishy aftertaste.

Studies have shown fish-oil capsules do seem to have cardiovascular benefits, including lowering blood pressure and reducing triglyceride levels. There's evidence, too, that capsules lower the overall risk for fatal heart attack (as does eating fish regularly). The results aren't all positive; for example, a study of people prone to sudden death from heart-rhythm abnormalities found that fish-oil capsules did nothing to reduce this risk.

Some experts think that fish oil may increase the risk of bleeding, a particular concern for people taking blood thinners (including aspirin). Gastrointestinal problems sometimes occur.

Most fish oil is sold as a supplement, so there isn't much government regulation. In the past, some brands of capsules have been found to contain toxins in independent tests conducted for consumer groups. The Consumers Union, which publishes Consumer Reports, is a good source of information, although access to much of it is restricted to subscribers.

The American Heart Association (AHA) says we all should be eating fish twice a week, but that people with heart disease should consume about a gram of EPA and DHA daily. But talk to your doctor before taking fish-oil capsules. And read the label carefully: Sometimes the capsule may total a gram (1,000 milligrams), only a fraction of which is EPA and DHA. In general, the AHA says it's better to eat fish than to take fish-oil capsules. Albacore tuna, herring, lake trout, mackerel, and salmon are all rich in EPA and DHA.

— Anthony L. Komaroff, M.D. Editor in Chief, Harvard Health Letter

Last updated:	September 05, 2008