Q: I’ve read about contaminants, such as mercury and PCBs, in fish. Am I better off taking fish-oil supplements than eating fish?
A: The answer to your question is not yet completely clear.
We know that the omega-3 fatty acids found in fish and fish-oil supplements are good for the heart. The American Heart Association recommends consumption of fish high in these acids to decrease the risk of coronary artery disease. The current suggestion is three portions of fish a week.
Unfortunately, fish today often contains more than just oils that are good for the heart — fish have become a repository for environmental toxins. The ones we are most concerned about are PCBs, organic pesticides (such as DDT) and mercury.
PCBsPCBs are chemical compounds that were used in the manufacture of electrical equipment before 1977. More than a billion pounds of these ended up in rivers and oceans, and have become concentrated in fish (some species more than others). And they are not going away — unless specifically cleaned up, PCBs appear to have become a permanent part of the environment.
PCBs and organic pesticides can have damaging effects on our reproductive organs, skin, immune and endocrine systems.
The highest levels of PCBs were found in anchovies, mackerel, cod and red mullet. Intermediate levels were in calamari, mussels and sole. Low levels were in scampi and cuttlefish. Meanwhile, a recent study in the Archives of Pathology and Laboratory medicine showed that PCBs are often more concentrated in farm-raised fish than in fish coming from the open water (though none of the fish listed above, except mussels, are extensively farmed). You are likely to find fewer contaminants, for instance, in wild salmon than its farmed cousin.
Like PCBs, pesticides (including DDT, a cancer-causing agent banned in 1973) have also permeated the ecosystem. They resist degradation and still show up in fish today. In the 1990s, DDT and associated chemicals were detected in 94 percent of fish samples.
Mercury from coal-burning energy sources is also present in bodies of water. High levels lead to heart disease and have devastating effects on the development of babies whose mothers have had significant exposure. Once mercury enters the body, it is stored in fat and remains there.
There have been many studies on the presence of mercury in fish. In general, the larger and older the fish, the higher its mercury level. Such levels are highest in shark, swordfish, king mackerel and tuna.
Fish-oil supplements seem to contain little, if any, of these environmental toxins. The recent study found non-detectible amounts in five brands of fish-oil capsules.
It’s impossible to know exactly what toxins you are ingesting along with your dinner. Taking fish-oil supplements instead may give you the benefits of fish without the risks of the accompanying toxins.
At this point, however, this is just food for thought. I am not suggesting that you stop eating fish. It’s a wonderful and tasty protein source. But whenever possible, go for wild fish and smaller, younger fish that originate in waters far from major centers of population and pollution.
Dr. Reichman’s Bottom Line: Though it’s unclear whether fish-oil supplements are safer than fish, if you are worried about environmental toxins, it couldn’t hurt to add fish-oil supplements and limit your fish consumption.
Dr. Judith Reichman, the “Today” show's medical contributor on women's health, has practiced obstetrics and gynecology for more than 20 years. You will find many answers to your questions in her latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," which is now available in paperback. It is published by William Morrow, a division of .
PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.