Children should be consuming considerably less canned tuna, otherwise their risk of serious mercury poisoning could become a public health issue in years to come, the Mercury Policy Project explained in a report issued yesterday.

The authors added that albacore tuna should never be given to children.

Children should not consume light tuna more than once per month if they weigh less than 55 pounds. Even kids weighing over 55 pounds should not eat tuna more than twice a month, the report stated.

In the USA, 52% of canned tuna is used for making sandwiches, 22% for salads, and 15% for other uses, such as casseroles, pasta dishes, and dried packaged meal mixes.

Most Americans have detectable levels of mercury in their blood, says the CDC (Centers for Disease Control and Prevention). According to WHO (World Health Organization), mercury levels in American people are considerably higher than in Western Europeans. The European Union tends to have stricter regulations regarding food and drink.

A member of the consumer group in the coalition that makes up The Mercury Policy Project, Sarah Klein, of the Center for Science in the Public Interest, said:

"Today we unfortunately have to bring consumers a warning about tuna. Despite its popularity, it should be a rare meal for children."

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59 samples of tuna from 11 different US states were tested, the authors explained. The tuna was bought in 4-pound cans or foil packages from catering companies that supply schools, or directly from the schools themselves.

Discrepancy in canned tuna mercury readings

Test results show mercury levels vary considerably from can to can. Even within a can itself, different parts have varying concentrations of mercury. There were also discrepancies with FDA (Food and Drug Administration) test results. The Mercury Policy Project had lower readings for mercury levels in light tuna and higher ones in albacore tuna compared to the results published by the FDA.

Despite the data presented in this new report, the FDA says it stands by its recommendations of a maximum of 12 ounces a week of canned light tuna and 6 ounces of albacore. Six ounces is the equivalent of an average can of tuna.

The Mercury Policy Project says that awareness of excessively high mercury concentrations in some fish has increased considerably over the last ten years. Pregnant women, especially, have become much more careful when shopping for food. However, whether or not fish consumption in school meals may pose a risk to health has been largely overlooked.

In it's 2011 Annual Report to the Governor, Legislature and Citizens of the State of Vermont, the Advisory Committee on Mercury Pollution recommended:

"....collaboration between the Vermont Department of Health and the Department of Education to communicate with Vermont schools and raise awareness among faculty, staff, and parents about the methyl mercury exposure risk to young children of consuming excessive amounts of tuna fish in school lunch programs."

Mercury levels in fish is a growing concern

The Californian State Water Resources Control Board announced in May 2011 that the presence of methylmercury and polychlorinated biphenyls (PCBs) in Californian sport fish is "widespread" and a concern for human health.

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A 2008 study carried out by The New York Times which examined 20 restaurants and retail outlets in Manhattan informed that those who eat just six pieces of tuna sushi per week could easily have blood-mercury levels above the US government safety limits.

What is mercury poisoning from food?

Mercury poisoning, also called hydrargyria or mercurialism is an illness caused by overexposure to mercury or its compounds. Mercury is a metal which can occur in several forms - all of which are potentially toxic. Mercury can be found everywhere, in water, rocks and in soil. Trace amounts of mercury also exist in the air.

Mercury in the air eventually settles onto land or water - rainfall washes the mercury on land into water. Some aquatic animals, such as specific types of fish and shellfish experience a buildup of methylmercury, a very toxic type of mercury that microorganisms convert. Shellfish and fish are the main sources of human methylmercury exposure.

Some types of fish, including tuna, shark or swordfish accumulate more methylmercury than others. How much is built up in their bodies depends on their age, how high up they are in the food chain, and what they eat. The higher up in the food chain a fish is, the greater its mercury accumulation.

The signs and symptoms of mercury poisoning caused by eating too many contaminated foods may include:
  • Peripheral neuropathy - tingling, itching, pins-and-needles on toes and fingertips
  • Reduced peripheral vision
  • Loss of coordination
  • Muscle weakness
  • Possible impairments in speech and hearing
  • Affected children may develop red cheeks, nose and lips; loss of nails and teeth; and some transient rashes
  • Children whose mothers had high mercury levels while pregnant may have cognitive problems as well as impairments in their central nervous system
Read a response to this article by registered dietitian with the National Fisheries Institute, Jennifer McGuire, MS., RD.

Written by Christian Nordqvist