Environment Food and Nutrition Health — 26 September 2012

Two new studies confirm the health benefits of eating fish, but urge consumers to avoid fish containing high levels of methyl mercury.

Fish is a solid protein source and a food staple in many countries, and has been praised for its role in reducing the risk of heart disease. Yet, there’s been some controversy as to whether the risks of fish consumption outweigh its benefits.

In a study published in the American Journal of Clinical Nutrition, researchers at Umea University in Sweden took hair and blood samples from volunteers in eastern Finland and northern Sweden. They compared blood from the patients who later suffered a heart attack with those who remained in good health – and found that while mercury content increased the chance of heart attack, omega-3 fatty acids decreased the risk.

Researchers said the higher risk of heart attack due to mercury consumption was only prevalent when there was a large amount of pollutants found in the body. If there was also a high level of omega-3 fatty acids from eating fish, the risk of a heart attack was low.

The study urgedsconsumers to find a balance in their fish consumption and to steer away from fish that contain the most mercury, such as mackerel, swordfish, and tuna. “Eat fish, but avoid fish with the most pollutants,” the authors said.

Mercury in Tuna

Another recent study focused on children. The Mercury Policy Project (MPP) warned that children should never eat albacore tuna because it could contain high levels of mercury.
The MPP report, called Tuna Surprise: Mercury in School Lunches, says children who weigh under 55 pounds shouldn’t consume canned light tuna more than once a month. And children weighing over 55 pounds should limit their tuna consumption to twice a month.

“We unfortunately have to bring consumers a warning about tuna. Despite its popularity, it should be a rare meal for children,” said MPP member Sarah Klein.

“Fish, including tuna, is generally a nutritious part of a healthy diet,” said  Klein.  “But especially for our littlest, most vulnerable children, we have to make sure the risks from mercury in tuna don’t outweigh tuna’s benefits.  We’re urging parents and schools to limit children’s tuna consumption and, when they do serve it, to choose lower-mercury options.”

MPP researchers analyzed 59 cans of tuna and found that mercury levels varied considerably from can to can – and sometimes within the can itself. Light tuna was found to have about one-third as much mercury as albacore.

Nearly a third of Americans’ total exposure to mercury comes from canned tuna.

“Most children are consuming only modest amounts of tuna and are not at significant risk,” said Michael Bender, MPP’s director. “So the focus really needs to be on kids who eat tuna often, to limit their mercury exposure by offering them lower-mercury seafood or other nutritious alternatives.”

Mercury Poisoning

Also referred to as mercurialism or hydrargyria, mercury poisoning is a medical condition caused by an overexposure to mercury or its compounds. Mercury is a heavy metal found in soil, rocks, water, and even air. Rainfall washes mercury from land into the ocean, causing some fish and shellfish to develop a buildup of methymercury. How much mercury a fish or shellfish has is dependent upon its age and what they eat. The higher up in the food chain, the more likely a fish is to have mercury accumulation.

The symptoms of mercury poisoning include:

  • A tingling sensation in the fingers and toes, known as peripheral neuropathy
  • Loss of co-ordination
  • Decrease peripheral vision
  • Weak muscles
  • Speech and hearing impairment
  • Rashes, and red lips, nose and cheeks (particularly in children)
  • Loss of teeth and nails (particularly in children)
  • Cognitive and central nervous system impairments (in children whose mothers were exposed to high mercury levels when pregnant).

Despite the MPP findings, the Food and Drug Administration (FDA) is holding to its recommendation of a maximum of 6 ounces of albacore and 12 ounces of canned light tuna per week.

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Elizabeth Magill

Elizabeth is a professional writer who holds an MBA. Liz focuses her writing on health news, medical conditions, healthy living, small business, career and work, and financial news. Her clients include The Motley Fool, LIVESTRONG.com, Healthline, HealthNews, Intuit Small Business Blog and many others. She’s author of multimedia App and Vook Conduct a Job Interview: The Video Guide.

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