From http://www.sciencenews.org/articles/20021221/food.asp

Mercurial Effects of Fish-Rich Diets
Janet Raloff

In the spring of 2000, one of Jane M. Hightower's patients had been concerned about hair loss, so the internist referred the woman to a specialist in her building. That dermatologist probed the woman's medical history but could find no explanation. That is, until she suddenly recalled a radio broadcast about mercury poisoning in people who had been eating lots of fish from tainted lakes. Their symptoms included hair loss.

Although the individual pieces of sushi are small, a meal of such bite-size seafood morsels could deliver a substantial dose of mercury, depending on the fish species selected and the waters from which they were pulled.

So, the dermatologist asked her patient if she ate much fish. Indeed, the woman said, she loved it. The doctor quickly arranged for the woman to get a blood test and then faxed the results back to Hightower. After reviewing the findings, which suggested the patient's mercury concentrations were in fact somewhat elevated, Hightower put the document atop the papers in her in-box.

Which is where it was still sitting, when a patient came in complaining, "My house is poisoning me!"

Hightower listened as the woman described how she sometimes felt so enervated that she could barely summon the will to get out of bed. Other times, especially while traveling abroad for months on end, the woman felt fine.

Oh yes, one other thing: The patient's thinning hair had become such a problem that the woman turned to Rogaine. She told Hightower she had been using this antibalding drug for 2 years.

Glancing at the in-box and her other patient's mercury data, Hightower asked whether her new patient ate much fish. "And she said, 'Yes, as a matter of fact—nine times a week,'" Hightower recalls.

This "serendipitous" pairing of cases launched the doctor on a quest to understand whether a taste for fish might be poisoning any of her other patients.

For the next year, Hightower formally surveyed the fish-consumption patterns of every person who came through her practice. Among those 720 people, 123 appeared to be eating fairly high concentrations of fish.

She then convinced 113 of these fish eaters—several of whom also showed symptoms indicative of possible mercury poisoning—to get tested for the metal. All but seven had blood drawn for testing. The remainder, including several children, submitted only their hair for testing.

Most of tested individuals exhibited elevated mercury concentrations despite having little or no known exposure to mercury besides eating fish, report Hightower and Dan Moore of the California Pacific Medical Center, also in San Francisco, in an upcoming issue of Environmental Health Perspectives. Among the patients who had blood tests, 89 percent had blood concentrations exceeding 5 micrograms per liter ( m g/L). Indeed, 16 percent had blood concentrations over 20 mg/L of blood—and 4 individuals surpassed 50 mg/L.

Because fetal exposure to mercury can later play out as IQ deficits, the National Academy of Sciences in 2000 recommended that women of childbearing age should try to keep mercury concentrations in their blood to less than 5 mg/L(or hair concentrations to below 1 mg/L). They didn't address other parts of the population.

Hightower advised all her patients with blood or hair values well above those cutoffs to pare fish from their diets over the next few months. And though follow-up blood tests showed that their bodies indeed began shedding mercury, the drop was slow. In some cases, even 21 weeks later, the patients' mercury concentrations remained elevated well above the NAS guideline figures.

Among adults, most symptoms abated as their blood concentrations dropped. Alas, Hightower says, that didn't spare one child, who initially was screened with nearly 15 times the NAS recommended ceiling concentrations for mercury. Hightower notes that this boy had experienced a documented "mental decline" during the 4 years he had regularly been eating not only canned tuna but also fresh tuna and salmon steaks. Though his parents eventually purged fish from his diet, the boy retains a significant neurological impairment, Hightower says.

Since her initial study ended, she has continued to evaluate fish consumption in her patients. Another 60 or so of them turned out to be at risk for subtle mercury poisoning. Perhaps most troubling, Hightower told Science News Online, was that her patients—much like herself—had viewed fish as a healthy food. Study after study had extolled the heart benefits of fish-rich diets. She asked: How could her patients have been so seriously misled? Why weren't they aware that this food can also serve as the vehicle for a potent poison?

In a Nov. 20 letter to President George Bush, she asked for actions to help consumers avoid unnecessary exposure. For instance, she requested that the government continue testing fish for mercury tainting and that the results—and any necessary fish advisories about mercury—"be readily available where fish are sold."


continued.......

References:

Bolger, P.M., and B.A. Schwetz. 2002. Mercury and health. New England Journal of Medicine 347(Nov. 28):1736.

Frustaci, A., et al. 1999. Marked elevation of myocardial trace elements in idiopathic dilated cardiomyopathy compared with secondary cardiac function. Journal of the American College of Cardiology 33(May):1578-1583.

Guallar, E., et al. 2002. Mercury, fish oils, and the risk of myocardial infarction. New England Journal of Medicine 347(Nov. 28):1747-1754. Abstract available at http://content.nejm.org/cgi/content/abstract/347/22/1747.

Hightower, J.M., and D. Moore. In press. Mercury levels in high-end consumers of fish. Environmental Health Perspectives. Abstract available at http://ehpnet1.niehs.nih.gov/docs/2003/5837/abstract.html.

Yoshizawa, K., et al. 2002. Mercury and the risk of coronary heart disease in men. New England Journal of Medicine 347(Nov. 28):1755-1760. Abstract available at http://content.nejm.org/cgi/content/abstract/347/22/1755.

Further Readings:

2002. Mercury associated with risk of heart attack. Johns Hopkins University press release. Nov. 27. Available at http://www.jhsph.edu/Press_Room/Press_Releases/fish_mercury.html.

Center for Food Safety and Applied Nutrition, Office of Seafood. 2001. References: Consumer advisory on methylmercury in commercial seafood. U.S. Food and Drug Administration (May). Available at http://www.cfsan.fda.gov/~dms/hgpdftoc.html.

Raloff, J. 2001. Landfills make mercury more toxic. Science News 160(July 7)4. Available at http://www.sciencenews.org/20010707/fob1.asp.

______. 2001. A dietary cost of our appetite for gold. Science News Online (May 12). Available at http://www.sciencenews.org/20010512/food.asp.

______. 2000. China: A mercury megapolluter. Science News 158(July 29):77.

______. 2000. Methylmercury's toxic toll. Science News 158(July 29):77.

______. 1991. Mercurial risks from acid's reign. Science News 139(March 9):152.