Some fish, such as swordfish, tilefish and king mackerel, tend to store more of the toxin in their flesh. Due to the risk for neurodevelopmental issues, the U.S. Food and Drug Administration has long advised pregnant women, women who may become pregnant, nursing mothers and young children to limit their intake of these and other fish and shellfish.
Among study participants in the top 20 percent of mercury exposure, average toenail mercury levels measured 0.7 micrograms per gram. Current U.S. advisories for sensitive subgroups aim at keeping mercury exposure below a level correlated with toenail levels of 0.4 micrograms per gram.
Not only was no link between mercury and higher cardiovascular disease found, the study said, but participants with higher mercury levels actually experienced slightly lower heart disease rates. Mozaffarian and his team attributed this to the other beneficial effects of fish consumption.
The authors noted that their research should not change advisories for eating fish with higher mercury levels among women who are or may become pregnant.
"There is no strong or moderate evidence that mercury has any effects in adults," Mozaffarian said. "So it's important and helpful that people can feel comfortable with fish as a normal part of their diet."
"It doesn't mean we can stop worrying about mercury in the environment," he added. "But for the individual consumer making a decision about eating fish, they can take this worry off the table."
One expert agreed that the study shouldn't cause Americans to feel any easier about mercury in the environment.
Elena Craft, a health scientist at the Environmental Defense Fund, acknowledged that the study looks at a much larger sampling than prior res
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