The dish on fish

You've heard that omega-3 fatty acids in fish can help prevent heart disease and maybe even curb Alzheimer's. Then you see an article suggesting that some fish are laced with contaminants such as Polychlorinated biphenyls (PCBs) and mercury. So, what's a fish eater to do? Stop worrying: there are still plenty of healthy fish in the sea, from wild and canned salmon to halibut and trout. The recently publicized multi-centre study found that farmed salmon contains higher levels of PCBs than wild salmon. Their farmed salmon samples contained 10 to 50 parts per billion (ppb) of PCBs compared to five ppb in wild fish. Farmed salmon tend to contain higher PCB levels than wild due to their concentrated feed. Because PCBs can increase cancer risk and the likelihood of having a child with reduced I.Q., the study authors recommend that Canadians consume no more than one farmed-salmon meal per month and two wild-salmon meals per week.

Health Canada and the U.S. Food and Drug Administration (FDA) say that eating salmon is safe. Both farmed and wild salmon fall well below their safe PCB levels of 2,000 ppb, so they say you can eat as much as you want.

"Fish is considered one of the best foods you can eat because of its high-quality protein and long-chain omega-3 fats," says Carolanne Nelson, Assistant Nutrition Professor at the University of Prince Edward Island in Charlottetown.

From a nutritional standpoint, two 85-gram servings a week can help lower heart-disease risk and blood pressure.

Unless otherwise stated, most Atlantic, restaurant and fresh supermarket salmon come from a farm. You'll also know by the price: fresh and frozen wild salmon is more expensive than lower-cost farmed salmon. Grilling fish without the skin will reduce the PCB content somewhat. If you're still concerned—despite Health Canada's assurances—consider asking for wild salmon or purchasing canned salmon, which is usually wild.

Too much mercury can cause brain and retina damage, particularly in unborn children. That's why Health Canada has always maintained that women should eat high-mercury swordfish, shark and fresh and frozen tuna in moderation and no more than once a month if pregnant and breastfeeding. (Although canned albacore tuna contains slightly more mercury than canned light tuna, both are considered safe by Health Canada. Albacore contains more beneficial omega-3 fatty acids.) For your healthiest choices, see best fishes.

Environmentalists, ecologists and some activist chefs have also expressed concerns about environmental damage and over fishing. Seafood Watch, an ocean-conservation project of the Monterey Bay Aquarium in California, for instance, publishes a list of best-choice seafoods, such as catfish and Pacific halibut, and ones to avoid, like Chilean sea bass and red snapper. If you're concerned, visit the Aquarium's Seafood Watch page for the entire list.

Best fishes The following types of seafood—listed with the most omega-3 rich choices at the top—are relatively low in mercury and PCBs and aren't considered to be over fished or fished in a manner harmful to the environment. Get two 85-gram servings per week. · Sardines · Canned and wild salmon · Farmed rainbow trout · Farmed striped bass · Canned albacore tuna · Farmed mussels · Dungeness, stone & Canadian snow crab · Pacific Halibut · Farmed oysters · Trap-caught, North American shrimp/prawns · Farmed catfish · Canned light (a.k.a. skipjack) tuna · Farmed clams · Rock lobster