Shorts - Canned Tuna Safety

Despite concerns about low-level mercury contamination in seafood, researchers and health agencies continue to urge people to eat fish. Fish is an excellent source of omega-3 fatty acids (EPA and DHA) as well as protein. An October 2006 article in the Journal of the American Medical Association concludes “For major health outcomes among adults…the [cardiovascular] benefits of fish intake exceed the potential risks. For women of childbearing age, benefits of modest fish intake, excepting a few selected species, also outweigh risks.” Yet, mercury in seafood poses a significant risk to the neurodevelopment of growing fetuses and young children. Its potential effects on adults, particularly subgroups such as the elderly or those with a genetic predisposition to Alzheimer’s, have received little, if any, attention. Signs of mercury toxicity include impaired concentration, learning ability, and physical coordination. Other signs include tremor, psychological disturbances, excessive perspiration, and hypertension.

The Environmental Protection Agency (EPA) and Food and Drug Administration (FDA) have struggled with the question of how to protect consumers without discouraging their consumption of this otherwise beneficial food. The U.S. Environmental Protection Agency has set a recommended limit on methyl mercury consumption (an organic form of mercury) at 0.1 micrograms/kg of body weight per day (1 microgram per 22 pounds). The EPA based this limit on evidence that mercury above 5.8 parts per billion in a woman’s bloodstream puts a developing fetus at risk of mercury poisoning. It takes six to 12 months for a woman’s body to remove mercury, according to Dr. William Weil. A person’s ability to eliminate toxic metal depends on several factors (such as available nutrients, liver health, genetics) and can greatly vary. Consequently, women who may become pregnant need to be cautious about mercury exposure.

In March 2004, EPA and FDA officials issued recommendations that women of childbearing age eat no more than 12 ounces of chunk light tuna a week or six ounces of albacore tuna (an older, larger fish that has more mercury). The guidelines do not address tuna consumption by men or older women. Young children are told to eat ‘smaller portions.’ According to the FDA, canned light tuna averages 0.12 parts per million of mercury in a can. Albacore tuna averages 0.35 parts per million. Under these guidelines, a 130-pound woman who eats one can (six ounces) of albacore tuna each week exceeds the EPA reference dose by 40 percent. A 45-pound child who eats one can of chunk white tuna each week consumes almost four times as much mercury as the EPA’s limit.

In actual practice, individual cans of tuna may contain far more mercury than the FDA average. Consumer Reports found that six percent of the light-tuna cans that it tested had higher mercury levels than the albacore average of 0.35 ppm -- as high as 0.85 ppm. Canned light tuna averages the highest amount of mercury in the FDA’s “fish with lower levels of mercury” category. FDA official Clark Carrington said that fish categories were arbitrarily chosen to put light tuna in the low category,’according to a Wall Street Journal article, in order to keep the market share at a reasonable level.’Researchers and health advocates have criticized the FDA for bowing down to the concerns of food companies and the tuna industry. Given this information, it might be wise to avoid albacore tuna, restrict the use of light-tuna, and eat more wild salmon, herring, and sardines, which are rich in omega-3 fatty acids.

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Hightower J. Mercury and Human Health: A Case Study in Science and Politics. Available at www.sfms.org. Accessed July 12, 2005.

Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health. [Abstract] JAMA 2006: 296(15). Available at http://jama.ama-assn.org/cgi/content/short/296/15/1885. Accessed March 12, 2007.

NOW with Bill Moyers. Food Fight: Mercury in Fish. Available at www.pbs.org/now.science/mercuryinfish.html. Accessed July 18, 2003.

U.S. Department of Health and Human Resources. Mercury levels in commercial fish and shellfish. (May 2001; updated February 2006). Available at juwww.cfsan.fda.gov/~frf/sea-mehg.html. Accessed March 31, 2007.

Waldman P. Mercury and Tuna: US Advice Leaves Lots of Questions. The Wall Street Journal. August 1, 2005; A1, A5.

Weise E. ‘Consumer Reports’ warns women about canned tuna. Available at www.usatoday.com/news/health/2006-06-05-tuna_x.htm. Accessed November 20, 2006.