I heard that farmed salmon might be dangerous for you. Is this really true? -- Anonymous

Maybe, especially if you're Canadian. A recent study made headlines when researchers found elevated levels of PCBs in British Columbia farmed salmon. It found that salmon raised in pens along the seacoast and fed fishmeal pellets to fatten them up had far higher levels of most contaminants, containing nearly 10 times the toxic load of wild salmon.

PCBs (polychlorinated biphenyls) are a dangerous class of manufactured chemicals that persist in the environment for many years. They were widely used in industry until concern about their health effects led to a North American ban in the late 1970's. PCBs have been linked to skin and liver damage, certain kinds of cancer, immune-system suppression, and reduced mental development in children.

Michael Easton, the geneticist who led the Canadian study, noted that the fish he tested had high residues of toxins because the feed used to fatten them and promote growth was full of PCBs and other pollutants. The fishmeal and fish oil fed to penned salmon can come from anywhere, including Third World regions where contaminants are not well regulated.

Keep in mind that this study was small. The researchers only looked at eight fish and five feed samples, so we don't know if these results apply to all populations of farmed fish. The results should be cause for concern, however, especially to Canadian fish lovers, who rely heavily on British Columbia salmon. (The U.S. population primarily uses farmed varieties coming from Norway and Chile, all of it called "Atlantic salmon" on menus and in markets.)

I've long recommended eating wild Alaskan salmon. Farmed salmon is lower in protein (because penned fish don't get to build up their muscles), higher in saturated fat, and lower in desirable Omega-3 fatty acids than wild salmon. It also contains residues of antibiotics and other drugs farmers use to treat diseases that occur in the unnatural crowded conditions of pens. Salmon farming is also ecologically disastrous, since the diseases it generates infect (and might eventually decimate) wild populations; the wastes it produces pollute coastal waters; and the feed fish it requires hasten the depletion of the ocean's resources. (It takes several pounds of feed fish to produce one pound of farmed salmon.)

I still recommend eating salmon because of the many health benefits it offers, including reducing risks of heart disease and cancer, decreasing inflammation, enhancing mood, and prolonging life.

Ask for wild Alaskan salmon in markets and restaurants; use some canned salmon, which is mostly "wild" because the softer texture of the farmed variety makes it unsuitable for canning. (Canned Sockeye or red salmon can be particularly good). Check the website of the Alaska Seafood Marketing Institute ( www.alaskaseafood.org

) for information and suppliers.

Also, look to other fish as sources of omega-3s, especially mackerel, sardines, and herring. Keep intake of farmed salmon down to once a week or less, and educate yourself about which kinds of fish are healthy choices. I recommend two websites: the National Audubon Society ( www.audubon.org

), which can send you a free Seafood Wallet Card for quick and easy reference as to which species are okay to eat, and the David Suzuki Foundation ( www.davidsuzuki.org

), which provides information about the environmental, social and economic costs of salmon farming. (David Suzuki is Canada's leading spokesman for environmental protection.)

Dr. Andrew Weil

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