by Kerry Grens, last updated: 30 August 2012NEW YORK (Reuters Health) - Mercury and the omega-3 fatty acids - the two are in the fish - appear to have opposite links for cardiovascular health, scientists have found.
In an analysis of 1,600 men in Sweden and Finland, researchers found that men with higher levels of mercury in the body had an increased risk of heart attack, while those with a high concentration of omega-3 had a lower risk.
Fish are considered to be part of a healthy diet, but the balance between the risks and benefits of these two potential compounds is not clear.
While the study cannot tease the cause and effect, researcher Maria Wennberg said there are ways to get fish oil naturally without much mercury, too.
"Two to three times a week, at least a meal of fatty fish, predators (such as salmon) and a consumption of predatory fish exceeding does not once per week of fish consumption can be recommended," Wennberg, Sweden Umeå University, told Reuters Health by email.
Predatory fish such as shark, swordfish, tilefish and king mackerel are at the top of the marine food chain and therefore concentrate mercury in the environment in their tissues.
The heavy metal is known to be toxic to the nervous system, especially in fetuses and children, and the U.S. Environmental Protection Agency advises women of childbearing age and children against predatory fish consumption.
Subject men to the new study, published in the American Journal of Clinical Nutrition, hair and the samples of blood to measure their mercury and the omega-3 levels, and information on their health and their way of life.
At the level of the average of mercury among Swedish men was 0.57 micrograms per gram of hair, while he was twice as high in their Finnish counterparts. Swedish, however, had higher levels of omega-3 as Finns.
The researchers found that men at least 3 micrograms of mercury per gram of hair had a slightly increased risk of heart attack than men to 1 microgram per gram, although they did not calculate the exact risk.
But this place only true if men were also low levels of omega-3 fatty acids. For men with more than fat, it took higher levels of mercury to see an increased risk of heart attack - suggesting that both compounds may have opposite effects on the ticker.
The results prove that high levels of mercury were responsible for the increase in the risk of heart attack, but merely that the two are related.
Dr. Dariush Mozaffarian of Harvard School of Public Health in Boston, said other factors, such as the low levels of education among those with high levels of mercury, may also be at work.
Previous studies by Mozaffarian, who was not involved in the new work, has not shown a link between mercury and heart attacks. But that research involved mercury much lower than in the present study.
He said that the new results probably do apply to most Americans, who have lower than males studied by Wennberg and his colleagues mercury. And few people have high levels of mercury and low omega-3, because the mercury in fish often comes with healthy fats.
Mozaffarian, it is likely that the Finnish men with high levels of mercury and low levels of omega-3 ate whitefish contaminated lakes in the North of the country.
Wennberg, said that its findings highlight the need to consider the omega-3 to study the link between mercury and disease.
SOURCE: http://bit.ly/PQ4CVi American Journal of Clinical Nutrition, August 15, 2012 online.
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