Omega-3 fatty acids and mercury, both found in fish, appear to have opposite affects on heart health, according to a northern European study.
Researchers, whose conclusions were published in the American Journal of Clinical Nutrition, looked at data from more than 1,600 men from Sweden and Finland to find that men with high levels of mercury in their body had an increased risk of heart attacks, while those with a high concentration of omega-3s had a lower risk.
Fish are considered part of a healthy diet, but the balance between potential risks and benefits from the two compounds is not clear.
Researcher Maria Wennberg said that while the study can't clarify cause and effect, there are ways to get fish oil naturally without getting a lot of mercury too.
"Fish consumption two to three times per week, with at least one meal of fatty, non-predatory fish (such as salmon) and an intake of predatory fish not exceeding once a week can be recommended," Wennberg, of Umea University in Sweden, told Reuters Health by email.
Predatory fish such as shark, swordfish, kind mackerel and tilefish are at the top of the marine food chain and for that reason concentrate mercury from 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 warns women of childbearing age and children against eating predatory fish.
The men in the study submitted hair and blood samples to measure their mercury and omega-3 levels, as well as information on their health and lifestyle.
The average mercury level among the Swedish men was 0.57 micrograms per gram of hair, and more than twice as high in their Finnish peers. Swedes, however, had higher levels of omega-3s than did Finns.
The researchers found that men with at least 3 micrograms of mercury per gram of hair had a somewhat increased risk of heart attacks compared with men with 1 microgram per gram, although they didn't calculate the exact risk.
But this only held true if the men also had low levels of omega-3 fats. For men with more of the fats, it took higher levels of mercury to see an increased heart attack risk, suggesting the two compounds might have opposite effects on the heart.
The results don't prove that the high mercury levels were responsible for the increased risk of heart attack, merely that the two are linked.
Dariush Mozaffarian, at the Harvard School of Public Health in Boston, said that other factors such as less education among those with high mercury levels could also be at work.
Previous studies by Mozaffarian, who was not involved in the new work, did not show a link between mercury and heart attacks, but that research involved mercury levels much lower than in the current study. SOURCE: http://bit.ly/PQ4CVi
Outbreak linked to heavy rains which encourage mosquito breeding
UN report warns that without measures to halt and reverse climate change, food production could become impossible in large areas of the world
It called for a "broad-based transformation of food and agricultural systems" to adapt to a warmer world, with an emphasis on supporting small shareholders.
A pre-COP22 ministerial meeting will be held in Morocco ahead of the conference to be held in Marrakech in November
Nearly 30-hour operation performed on 13-month-old boys
Among the world's wealthier regions, North America had the worst healthy life expectancy at birth for both men and women.
Diminishing coal in the energy mix must become a government policy in EU towards a low carbon economy: European think-tank
'Developing countries should be given access to nuclear power,' says International Atomic Energy Agency director
More people in the world are obese than underweight
Epipen maker Mylan has agreed to pay $465 million to the US government
3 of 4 transplants from living donors removed; scientists hope remaining transplant successful
Air monitoring station clocks dangerously high levels of smog
EU ministers have agreed to ratify the landmark Paris climate agreement
The man in the western state of Utah became ill after helping to take care of his 73-year-old father, who was hospitalized in June with Zika after being infected during a trip to his native Mexico.
Children in Kenya make up 10 percent of all tuberculosis cases
Health Secretary Paulyn Ubial said 12 cases of Zika had been detected across the Philippines this month, including a 22-year-old woman from the central island of Cebu who is 19 weeks' pregnant with her first child.