NEW YORK (Reuters Life!) - The benefits for heart health of eating fish may outweigh concerns over the potential negative impact of increased exposure to mercury as a result, according to a study.
But restrictions are still needed in connection with fish high in mercury, which include species such as perch, shark, swordfish and halibut, said a Swedish team whose results were published in the American Journal of Clinical Nutrition.
Maria Wennberg, a public health researcher at Umea University in Sweden, and her colleagues studied more than 900 Swedish men and women who answered questionnaires about the amount of fish in their diet. The team also analyzed the subjects' red blood cells for levels of mercury and selenium.
Mercury levels were generally low for Scandinavians, but people whose red blood cells showed higher amounts of mercury did not have a higher risk of cardiac problems.
"The protective nutrients in fish override any harmful effect of mercury at these low levels of mercury," Wennberg said.
The American Hearth Association recommends that people consume at least two servings of fish a week. Salmon, mackerel and albacore tuna are especially high in omega-3 fatty acids, which are thought to minimise the risk of coronary heart disease.
But some questioned the findings, with David O. Carpenter, director of the Institute for Health and the Environment at the University at Albany, in Rensselaer, New York, saying that the researchers had assumed the mercury in the subjects' blood had come from fish.
Carpenter, noting that there were other potential sources, such as coal-fired power plants and dental fillings, added that fish in the Baltic Sea, which borders Sweden, were high in levels of other toxic compounds such as PCBs, which complicated the results.
Wennberg and her colleagues said as well that the drawbacks of relying on the subjects' memories about the amount of fish consumption could also have an impact on the results.
But they said one finding warranted more study: that subjects whose red blood cells contained elevated traces of selenium appeared to be at increased risk of sudden cardiac death.
Reporting by Adam Marcus at Reuters Health; editing by Elaine Lies