Q & A Library

Fresh fish is delicious and good for you. There's no trick to figuring out what to buy, but you should keep a few simple rules in mind. In general, ocean fish are preferable to freshwater fish because they're less likely to be contaminated by pollutants. Sardines and herring are good sources of omega-3 fatty acids, which can protect against heart attacks and cancer, decrease inflammation, and enhance mood and long-term health. They're also healthier choices because they're less likely to be contaminated than large carnivorous fish such as swordfish and marlin, which spend a lot of time in coastal waters where pollution levels are highest. If you can find fresh sardines or herring, try them; they are quite different from the familiar canned versions.

I avoid bluefish, another oily species, because they tend to concentrate mercury. Albacore tuna and mackerel are good sources of omega-3s, but I do not eat them for the same reasons that I avoid swordfish and marlin. My favorite fish is wild Alaskan salmon, which is delicious, contains plenty of omega-3s, and is relatively toxin-free. However, you may have trouble finding wild salmon in many parts of the country. Avoid farmed salmon (also called Atlantic salmon), which is what you mostly find in supermarkets and fish markets. While less expensive than wild salmon, farmed salmon also may have a higher and less favorable omega-6 to omega-3 ratio and may contain residues of antibiotics and other drugs used by fish farmers to treat diseases in their farming pens. What's more, recent studies have detected levels of PCBs and other contaminants in farmed salmon that are 16 times higher than those found in wild salmon.

When buying fish, you can determine freshness by following these suggestions from the U.S. Food and Drug Administration:  

• The fish's eyes should be clear and should bulge a little.
• The flesh (whether the fish is whole or filleted) should be firm and shiny.
• Gills should be bright red and free from slime.
• The flesh should spring back when pressed.
• There should be no darkening around the edges of the fish or brown or yellowish discoloration.
• Buy only fresh seafood that is refrigerated or properly iced.
• Don't buy cooked seafood, such as shrimp, crab, or smoked fish if it is displayed in the same case as raw fish. Cross-contamination can occur.
• Don't buy frozen seafood if the packages are open, torn, or crushed on the edges

You can get a handy pocket guide to fish choices (both good and bad) from the Environmental Defense Fund at: www.environmentaldefense.org/documents/1980_pocket_seafood_selector.pdf

Andrew Weil, M.D.