It's time to get hooked. Fish, long regarded in folklore as a wonder food, now has scientific backing as a major nutritional player. Abundant evidence supports fish's reputation for preventing and fighting myriad diseases, from heart disease and cancer to arthritis and mental illness. A rich source of low-fat protein, fish contains generous amounts of calcium, phosphorus, iodine, iron, and vitamins A and D. But its biggest benefit are two long-chain omega-3 fatty acids, called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Heart specialists have long recommended that their patients eat fish because it's well known that EPA and DHA keep hearts healthy. A 17-year study published in the New England Journal of Medicine found that men with no heart-disease history who had high blood levels of omega-3s were less likely to die suddenly from heart disease than those with low levels of omega-3s (2002, vol. 346, no. 15). Separate research made a similar finding in women (Journal of the American Medical Association, 2002, vol. 287, no. 14). In addition, fish eaters show evidence of healthier triglyceride levels, reduced blood pressure, and a lowered risk of blood clots and stroke.

Experts say it's the pervasiveness of these essential fatty acids in fish that make seafoods so helpful to your body. "When you eat fish, the omega-3 fatty acids get on every cell membrane and affect every system in the body," says Artemis Simopoulos, MD, director of the Washington, D.C.-based Center for Genetics, Nutrition, and Health and coauthor of The Omega Diet (HarperCollins, 1999). Scientists continue to gather evidence that omega-3 fatty acids in fish may also reduce cancer growth; calm the ill effects of Alzheimer's and depression; fend off diseases related to inflammation, such as rheumatoid arthritis, asthma, psoriasis, and Crohn's disease; and even halt the development of diabetes. "Diabetes prevention is the next wave in omega-3 research," predicts Joyce Nettleton, DSc, RD, a specialist in seafood nutrition and the author of Omega-3 Fatty Acids and Health (Kluwer Academic, 1995). Nettleton refers to a preliminary National Institutes of Health-sponsored study involving a group of Alaskan Inuit who showed early signs of developing type 2 diabetes. After four years of eating less saturated fat and more fish, as well as exercising more and reducing weight when appropriate, not one of the 39 subjects developed the condition (Sven Ebbesson, PhD, presentation at the International Workshop on Omega-3 Fatty Acids, Diabetes, and Cardiovascular Risk, Bethesda, Maryland, November-December 2000).

Two Servings Per Week
Healthy individuals need only two servings of fish each week to reap the benefits, including at least one serving of oily fish. This category includes salmon, sardines, herring, mackerel, and canned albacore tuna, which contain significant amounts of omega-3s (see right). But because almost all fish contain these fatty acids in various concentrations, it's easy to get fish-based omega-3s into your diet. For example, enjoy a smoked-salmon sandwich for lunch or toss canned tuna chunks into your evening salad, and bake a less-oily fish (such as halibut, snapper, rainbow trout, or freshwater catfish) with a squeeze of lemon for a quick weeknight dinner.

As always, a balanced diet is best; don't ignore other healthy foods as you up your intake of any important nutrient, including omega-3s. Certain plant foods, such as canola oil, soyfoods, flaxseed, and walnuts, also contain healthy fats in a form called alpha-linolenic acid (ALA). But keep in mind that it takes up to ten times more plant-based ALA to obtain the amount of omega-3s you get from an average serving of fish, says Simopoulos.

What About Mercury?
Although fish deserves its nutritional acclaim, recent FDA warnings for pregnant and nursing women and women of childbearing age have raised concerns. In question are fish containing high mercury levels—those caught in polluted waters in areas such as New York, the Great Lakes region, and Florida, as well as large predatory fish, including shark, swordfish, king mackerel, large tuna, and tilefish, which eat high on the food chain and therefore can accumulate large amounts of mercury over time. The FDA recommends that if you're pregnant or could become so, limit your intake of fish to 12 ounces per week, and don't eat fish listed as problematic. The Environmental Protection Agency (http://map1.epa.gov) and the Environmental Working Group (www.ewg.org) provide updates on which fish are best avoided or eaten with caution.

Still, childbearing women might not want to avoid eating fish altogether, Nettleton says, because DHA from fish aids fetal and infant neural development. She recommends eating a variety of fish that are high in omega-3s and low in contaminants, such as salmon, rainbow trout, sardines, herring, and pilchard, as well as seafood with lesser quantities of omega-3s, such as sole, flounder, haddock, farmed catfish, and shellfish. Keep the precautions in mind, but don't go overboard; fish's benefits are too good to ignore.

Kimberly Lord Stewart is a health and food freelance writer.