Study of mercury in fish raises concerns, calls to strengthen government guidelines
An environmental research organization is urging the federal government to strengthen its proposed advice about what types of fish pregnant women should eat over concerns about potential exposure to mercury.
The 2014 draft recommendations from the U.S. Food and Drug Administration and the Environmental Protection Agency advise women who are pregnant, nursing, or may become pregnant to eat 8 to 12 ounces, or two to three servings, of a variety of low-mercury fish each week. The draft identifies lower mercury fish as salmon, shrimp, pollock, tuna (light canned), tilapia, catfish and cod. It suggests avoiding tilefish, shark, swordfish and king mackerel. The current and draft guidelines advise pregnant women and women who are breast-feeding to limit eating white (albacore) tuna to 6 ounces a week.
But a new study by the nonprofit Environmental Working Group suggests the guidelines aren’t specific enough, and could lead women to eat too much of the wrong kind of fish, especially other forms of tuna.
The EWG tested hair samples from 254 women of childbearing age from 40 states who reported eating as much or slightly more fish than the government recommendations over a period of two months. The study found that 29 percent of women had more mercury in their bodies than the level the EPA considers safe, 1 part per million.
EWG has advocated for a stricter mercury limit of 0.58 ppm. Almost 60 percent had more mercury in their system than that stricter limit, according to Dr. Philippe Grandjean, adjunct professor of environmental health at the Harvard T.H. Chan School of Public Health, who tested and analyzed hair samples for EWG’s study. Grandjean said that the limit of 1 ppm was calculated in 2000 and the lower recommendation is based on updated research from 2007.
The study found that mercury levels in women who frequently eat fish are 11 times higher than in women who rarely eat seafood. Although the study participants eat more than twice as much fish as the average American, almost 60 percent still don’t get the amount of omega-3s recommended during pregnancy from seafood in their diets.
“That’s really bad,” Grandjean said. “It means that people are eating the wrong kind of fish, thinking that they are really eating a healthy and balanced diet, and they’re not.”
Sonya Lunder, study author and senior analyst at EWG, emphasizes the need for updated federal recommendations.
“I have followed this issue for almost a decade, and I have to say I was very surprised by the number of women who exceeded the EPA guidelines,” Lunder said. “I want to make it clear we support the idea that seafood can be a healthy beneficial choice during pregnancy. Omega-3s support healthy development and a healthy baby. We want to encourage seafood consumption, but as women begin to eat more seafood, they have to keep that mercury information in front of them and in their mind so they don’t go in the wrong direction and suffer from the risks rather than the benefits.”
The FDA and EPA are in the process of revising the advice on this issue.
Mercury exposure during pregnancy can significantly alter the developing brain and nervous system of the unborn baby and cause lifelong deficits in learning, memory and reaction times, according to the study. There are also issues for women who are not pregnant, as well as men: Mercury can have toxic effects on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes, according to the World Health Organization.
Study participants reported eating higher amounts of tuna steaks, tuna sushi and other fish with high levels of mercury. Tuna accounted for about 40 percent of the mercury consumed by participants. But the FDA and EPA don’t identify them as fish pregnant women should avoid.
The four types of fish the FDA recommends pregnant women do not consume — swordfish, shark, king mackerel and tilefish — represent 6 percent of exposure, said Michael Bender, director of Mercury Policy Project and coordinator of Zero Mercury Working Group.
Gavin Gibbons, a spokesman for the National Fisheries Institute, disagreed with Bender’s assessment. The FDA guidelines go “species by species and talk about what the upper end limits are that pregnant women could eat,” he said, and “hundreds of studies” show women are not being harmed by seafood and might not be eating enough.
“This type of study can scare pregnant women unnecessarily away from a healthy protein that includes essential fatty acids for their baby’s brain and eye development,” he said.
Registered dietitian Lisa Drayer, who was not involved in the study, agrees the federal government should update recommendations to include a limit on tuna and an increase in wild salmon. She also encourages the consumption of low-mercury, high-omega-3 fish, such as anchovies, herring, trout and sardines.
Wild salmon provides a good dose of omega-3s, which are very important for a growing fetus and play a major role in brain and eye development, earlier studies have shown.
“You can consume a lot of fish but you really want to get the biggest bang for your bite,” said Drayer. “My advice is to toss the tuna. Pregnancy is not forever. In the scheme of life, nine months is a small sacrifice to make for a growing fetus.”