While a Rich Source of Protein, Fish Also Poses Potential Risks
We’ve all heard that fish is a healthier alternative to red meat, and there’s good reason for that.
Fish is a rich source of protein, typically low in saturated fat, which is the type of fat that contributes to unhealthy cholesterol levels. Some fish may also contain fat that is good for your heart, such as the omega-3 fatty acids that you may have heard about. Studies show that regular consumption of fish containing omega-3 fatty acids is associated with a lower risk of heart disease.
With this in mind, Valerie was looking forward to eating lots of fresh, tasty fish as she prepared to leave on a seaside vacation. The vacation came, but the fish--though fresh and plentiful--were eaten only sparingly. In this case, the health benefits of eating fresh fish were outweighed by the risk for this nursing mother of eating fish contaminated with toxins.
Federal guidelines recommend that nursing moms stay away from fish that are likely to be highly contaminated.
In California, methylmercury and polychlorinated biphenyls, or PCBs, are the contaminants of most serious concern.
Mercury, a naturally occurring element, accumulates in rivers and oceans. In the water, mercury is converted into a highly toxic form called methylmercury, which is ingested by fish.
PCBs are a group of more than 200 industrial chemicals. Although PCBs have not been manufactured in the United States since the late 1970s, they still persist in the environment and, like methylmercury, tend to concentrate in fish.
When consumed in sufficient amounts, these toxins can cause a variety of problems. Methylmercury predominantly affects the nervous system; PCBs, on the other hand, can damage several organ systems and may increase the risk of developing certain types of cancer.
Methylmercury and PCBs may pose additional dangers to developing fetuses, as these toxins can pass through the mother’s placenta.
Studies suggest that methylmercury can adversely affect the developing brain, causing problems with memory, attention and language; PCBs have been associated with lower IQ scores and low birth weight. Infants, who can be exposed through a mother’s breast milk, and young children are also thought to be particularly sensitive to the effects of these toxins.
The amount of toxins vary depending on the type of fish. In the United States, average methylmercury levels in swordfish, for example, are about 1 part per million, while levels in catfish are only 0.07 part per million.
Where the fish live also affects their toxin levels. Fish caught in waters near waste sites contaminated with PCBs, for example, may contain significantly higher concentrations than those caught in waters that are distant from such sites.
The Food and Drug Administration has set limits on the amount of PCBs and methylmercury that commercial fish can contain. Some types of fish sold in markets and restaurants come very close to those limits, and could pose a risk if eaten in excess .
The FDA recommends that pregnant women, nursing mothers and young children not eat shark, swordfish, king mackerel and tilefish because these fish often contain high levels of methylmercury.
Women of childbearing age who may become pregnant are also advised to avoid these types of fish as methylmercury can build up in their bodies over time, and may cause problems if they become pregnant later. Up to 12 ounces per week of cooked fish, however, can be safely eaten.
The Environmental Protection Agency has issued additional guidelines for noncommercial, or sport, fishing. The agency advises pregnant women, women of childbearing age who may become pregnant and nursing mothers to limit their consumption of freshwater fish caught by family and friends to one meal per week, or about 6 ounces of cooked fish. Children should eat no more than 2 ounces per week, the agency says.
For the rest of us, it’s a good idea to check for sport-fish health advisories from the California Department of Fish and Game and California Environmental Protection Agency. For example, a current advisory warns against eating white croaker caught in Los Angeles Harbor because the fish has been found to contain high levels of PCBs and the pesticide DDT.
The absence of an advisory about fish in a specific area does not necessarily mean they are safe to eat. In California and other states, fish safety has not yet been completely evaluated.
You can reduce your health risks by taking some simple precautions. Vary your choice of fish, avoiding those that are known to have levels of contaminants.
When preparing fish yourself, select smaller fish because they tend to have lower concentrations of methylmercury and PCBs than larger fish).
Remove the skin, trim away visible fat and gut the fish before cooking them. (Some toxins--PCBs, for example--tend to concentrate in the fat and guts.)
Select a cooking method, such as baking, steaming or grilling, that allows the juices to drain, and do not use these juices to make sauces or stocks.
When sport fishing, vary the locations that you fish. Also, check local advisories for warnings about specific toxin problems and look for posted warning signs along the water’s edge.
For a list of fish advisories in California, contact the Office of Environmental Health Hazard Assessment by phone at (916) 327-7319 or at the agency’s Web site at https://www.oehha.ca.gov/fish.html.
Health advisories are also included in a booklet published by the California Department of Fish and Game called “Sport Fishing Regulations.” The booklet is available wherever fishing licenses are sold.
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Dr. Jonathan Fielding is the director of public health and the health officer for the Los Angeles County Department of Health Services. Dr. Valerie Ulene is a board-certified specialist in preventive medicine practicing in Los Angeles. They can be reached by e-mail at ourhealth@dhs.co.la.ca.us. Our Health runs the second and fourth Mondays of each month.
