It’s a whopper of a fish story. And, unfortunately, some consumers are swallowing it — hook, line, and sinker. For years the fishing industry has worked overtime to persuade Americans to ignore well-founded concerns about mercury and other pollutants in fish.
Now the industry is hailing a new report commissioned by the National Oceanic and Atmospheric Administration as more evidence that fish is a healthy food. But as a physician and a nutritionist, we are deeply skeptical of the industry’s spin campaign. Heart disease can be warded off by wise food selections, but fish is not an optimal choice. High levels of methyl mercury, organochlorines, polychlorinated biphenyls (PCBs), and other environmental toxins accumulate in fish.
These toxins are known to affect nervous-system development, the immune system, heart health, bone integrity, and pregnancy outcomes.
Even those who endorse fish consumption readily admit that contamination is a pervasive problem. The NOAA-commissioned report, for example, contains a complicated flowchart noting that “contaminants in seafood vary according to local conditions.”
In truth, fish consumption is already Americans’ primary source of exposure to mercury, a potent neurotoxin that can harm developing fetuses. Some of the most polluted species, such as albacore tuna, are also among the most popular with consumers.
The risks are especially acute for certain populations. A new study links fish consumption among pregnant women to an increased risk of premature birth. The Pregnancy Outcomes and Community Health study, conducted by researchers at Harvard and Michigan State Universities, showed that mercury levels in maternal hair were higher when fish consumption was increased.
Women who delivered preterm were three times as likely to have had mercury levels in their hair at or above the 90th percentile, compared with those who delivered at term.
Proponents defend fish consumption as a boon to cardiovascular health. That’s because some species contain omega-3 fatty acids, which may help guard against heart disease. But fish are also surprisingly high in cholesterol and artery-clogging saturated fat, which accounts for 15 to 30 percent of fish fat. Chinook salmon, for example, derives 55 percent of its calories from fat, and some species are higher in cholesterol than steak. Only part of the fat in fish is omega-3; much of the remaining fat is saturated.
That raises an important question: Why not avoid fish and obtain omega-3 fats from walnuts or other healthy plant sources, which have no cholesterol or methyl mercury? In fact, a new study in the American Journal of Cardiology shows that adding walnuts to a high-fat meal reduces negative changes in arteries. Walnuts increased the elasticity and flexibility of the arteries by 24 percent for those with high cholesterol.
It would also be prudent to consider that there may be no significant benefit to consuming a diet high in omega-3s. A recent review in the British Medical Journal found no evidence to support the assertion that eating oily fish improves heart health. In fact, the review found that consumption of omega-3 fats does not have a clear effect on heart health or survival.
But there is a well-supported way to guard against heart disease: Avoid animal products. A 2003 study in the Journal of the American Medical Association showed that vegetarian diets lower cholesterol levels almost as powerfully as cholesterol-lowering drugs. People who consume plant-based diets tend to be slimmer than meat-eaters, and they experience lower rates of heart disease, diabetes, high blood pressure, and other life-threatening conditions linked to overweight and obesity.
It’s no surprise that the fishing industry wants to sell Americans more fish. But savvy consumers will think twice before taking the bait.
Hope Ferdowsian, M.D., is a public-health specialist with the Physicians Committee for Responsible Medicine. Susan Levin is a PCRM nutritionist.
Physicians Committee for Responsible Medicine