Good Fish, Bad Fish: Which Fish is Best For You?
From Focus on Healthy Aging - January, 2007
Experts suggest keeping fish on the menu, but avoid the high-mercury varieties.
Fish is a good source of protein, it’s low in saturated fat, and it contains heart-healthy omega-3 fatty acids, but many types of fish also contain dangerous levels of mercury. So, should you eat fish?
“If you had a heart attack, have coronary heart disease, or even are at high risk for heart disease, any risks from eating fish are offset by the benefits,” says Donald A. Smith, MD, MPH, director of Lipids and Metabolism at the Mount Sinai School of Medicine. An October 17 Institute of Medicine Report (IOM) came to the same conclusion.
Many studies have touted the heart benefits associated with fish. For example, a study in the October 18 issue of the Journal of the American Medical Association found that eating salmon and other fish high in omega-fatty acids once or twice a week can cut the risk of death from heart disease by about a third.
Risks of mercury exposure
Still, you can’t completely ignore the risk of mercury exposure, which at high levels can harm the brain, heart, lungs, and immune system. Nearly all fish and shellfish contain trace amounts of mercury. However, larger fish that have lived longer have the highest mercury levels because they have had more time to accumulate it.
Cold-water fish such as salmon and herring are best because they have high levels of omega-3 fatty acids and low levels of mercury. Many shellfish, such as shrimp, clams, and oysters, contain undetectable levels of mercury, and also have omega-3 fatty acids. Catfish, flounder, Pollock, and cod are also good choices. Tuna is high in mercury levels, so limit consumption to once a week. Eat canned light tuna instead of albacore tuna, since albacore tuna is more likely to accumulate mercury. Stay away form large fish such as swordfish, shark, king mackerel, and tilefish, which have the highest mercury levels.
Does it matter where the fish comes for? Yes. Though farm-raised fish and fish caught in the wild have similar amounts of omega-3 fatty acids, farm-raised fish may have higher levels of contaminants due to toxins present in their feed, officials say. But, be prepared to dig deeper into your pocket when purchasing wild fish, because they’re usually more costly.
Other heart-healthy sources
Fish is not the only source of omega-3 fatty acids. Other sources include flaxseed, canola oil, and broccoli. Fish-oil supplements containing omega-3 fatty acids are also available and are a good alternative for people who don’t like fish. Before taking fish-oil supplements, though, talk to your doctor. He or she can advise you on the right dose and can recommend a reputable manufacturer.
Dr. Smith recommends that you eat fish twice a week, or take one-to-two fish-oil capsules per day, to get the 800-900 milligrams of the essential fatty-acid ingredients eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) you need for the life-saving benefit.
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