As South Beach Diet followers already know, fish — particularly oily fish, like salmon and lake trout — is rich in heart-healthy omega-3 fatty acids. However, not all fish is created equal: We also regularly caution against eating fish high in mercury (including tilefish, swordfish, and king mackerel). If this seemingly conflicting advice leaves you confused about the benefits and risks of eating fish, read below. Our fish facts will help you sort through the science.

 

1. Fatty fish helps fight heart disease. Numerous studies have determined that the two omega-3 fatty acids found in fish, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), help make the blood less sticky and, thus, less likely to clot and cause heart attacks and strokes. There is also compelling evidence that omega-3s fight the inflammation process, which is important since inflammation is thought to be involved in many diseases, including heart disease, diabetes, and arthritis. Dr. Agatston recommends adding fish to your weekly menu — just two servings a week will provide the benefits. (Check with your doctor to see if you should also be taking a fish-oil supplement.) Omega-3s are most concentrated in sardines, salmon, and mackerel.

    

2. Wild fish is the way to go. Farm-raised salmon contains the environmental toxins PCBs (polychlorinated biphenyls), which may be associated with an increased risk of cancer. This salmon is contaminated because its food contains PCBs. Salmon store the PCBs in its fat, where it can accumulate, just as it does in humans who eat contaminated fish. The best way to avoid ingesting PCBs is to choose wild salmon whenever possible. Canned and pouched salmon are a convenient source in your supermarket. However, there is a way to reduce the PCBs in farmed salmon: Remove the skin (and the fat beneath the skin) before you cook it, and broil, bake, or grill the fish to allow the fat (again, where PCBs accumulate) to drain off. Of course, this will lower the omega-3 content as well, but you'll still get some of its benefits.

    

3. Pregnant women, nursing mothers, and women considering pregnancy should limit exposure to fish containing methylmercury. This industrial pollutant is most concentrated in long-lived, deep-sea species, like shark, swordfish, king mackerel, and tuna. While adults have a higher threshold and are affected only by high levels of mercury (which can cause neurological damage and vision problems), even low levels can impede the development of the nervous system in fetuses, babies, and young children. The best way to avoid mercury exposure is to eat small fish, like cod, sole, halibut, and shellfish that larger fish feed on. It's also advisable to vary your seafood selection — as well as avoid high-mercury species.