Nutritionist Beware: Risk Based Studies Confuse Consumers on Seafood Advice

Whenever a new scientific study is released, the press immediately searches for the headline. But too often that means oversimplifying or overemphasizing the most provocative results while ignoring the messy and complex evidence beneath.

Take the recent study funded by the National Institute of Environmental Health Sciences (NIEHS). It concludes that the neurocognitive benefits of aerobic exercise may be blunted by high levels of mercury exposure. In fact, more than 90 percent of the participants in the study were exposed to levels of methylmercury above EPA limit of 5.8 mcg/L.

To a lay reader in the U.S., that might sound alarming. But it’s important to look beyond the headline. In this case, the research population came entirely from the Faroe Islands, located 200 miles north of England, where high-mercury whale meat is a major component of the diet.

But Americans—who eat far less fish, and virtually no whale meat to speak of! —have average levels of mercury far below the study population’s, and well within EPA recommended limits. So the study is of limited use. Especially since it doesn’t detail what other types of fish the test population were eating, or how much.

The NIEHS  press release does wisely cite the FDA draft advice for pregnant women and children on recommended levels of seafood consumption. This advice is in turn based on the FDA’s 2014 Net Effects report, which looked at over 100 scientific studies analyzing both the risks and the rewards of seafood consumption.

By contrast, the NIEHS study focuses solely on risks, without considering the rewards. That’s fine as a piece of research, but less helpful in informing life decisions. It’s like a study about whether you should buy a car that focuses only on auto accidents.

In the case of seafood consumption, the science is abundantly clear: the health benefits of eating fish greatly outweigh any hypothetical risks. The Omega-3 fatty acids contained in fish are essential for healthy brain and eye development, and long-term cardiovascular health. One long-term NIH study showed that children whose moms cut back on seafood during pregnancy had significantly lower developmental and IQ outcomes.

That’s why following the 2015 – 2020 Dietary Guidelines for Americans—which recommend eating more fish than most Americans currently do—is so critical. Pregnant women should have two to three servings of fish a week, while avoiding four fish high in mercury: tilefish from the Gulf of Mexico, shark, swordfish, and king mackerel.

Rima Kleiner, MS, RD

National Fisheries Institute