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
'The level of alarm is extremely high,' says WHO head, calls for an emergency meeting
One person has tested positive in Denmark for the mosquito-borne Zika virus
The world is making 20 times more plastic than we did 50 years ago with the majority being dumped in the sea.
Colombia's government has signed new legislation for the regulation and legalization of cannabis to be used for medicinal purposes.
Scientists predict Earth will become increasingly hostile for mankind as it warms, with disastrous storms, floods and droughts, and rising sea levels that will consume islands and eat away at populated coasts
Hundreds of thousands of climate activists have descended on Paris ahead of the UN Climate Conference and are preparing to defy a ban on street protests joining thousands of protestors around the world.
'This is all bad news for the planet,' head of the World Meteorological Organization says
UN agency calls for urgent climate deal as hundreds of thousands fall victims to weather disasters
Fifty grams of processed meat eaten daily increases risk of colorectal cancer by 18 percent, say experts
COP21 conference aims at securing a pact on greenhouse gases that would limit global warming to two degrees Celsius over pre-industrial times.
Earth is on track for average warming of 2.7 degrees Celsius by 2100, exceeding UN's anticipation
The London Project to Cure Blindness was established a decade ago to try to reverse vision loss in patients with age-related macular degeneration
Improvement has been seen around the globe, even in the key tropical rainforests of South America and Africa
Christiana Figueres says there is 1.2 million euros deficit to cover upcoming sessions
Some of the world's major cities, most Pacific island nations are at risk of disappearing due to rising seas
Yemen forces allied to the Houthi have launched a scud missile toward southern Saudi Arabia