Good Fish, Bad Fish

"In fact, some children actually did better on tests," notes the Seychelles study's lead investigator, Gary Myers, a professor of neurology and pediatrics at the University of Rochester Medical Center in New York. "We don't think that is related to mercury consumption, of course, but to fish consumption" and the higher amount of omega-3 fatty acids it contains. Similar results were reported in October from a continuing study in England.

One theory is that the mineral selenium may help protect against mercury contamination. Selenium is present in deep-water seafood at five to 20 times the concentration of mercury. When the two chemicals bind, methylmercury appears to become harmless.

While the selenium theory is still under investigation, "the conclusion [for now] is to tell people to continue to consume fish," notes Conrad Shamlaye, an epidemiologist and part of the Seychelles study.

What makes the Seychelles experience especially relevant is that the fish eaten there contain nearly identical levels of mercury as does the seafood consumed in the United States. The difference is that people in the Seychelles "consume 10 times the amount of fish that we do here," Myers says, noting that his study has found no ill effects in children whose mothers ate a lot of mercury-containing seafood during pregnancy.

As Myers notes, "the entire population of Japan also has methylmercury levels that are above the Environmental Protection Agency's reference level for methylmercury, and they don't seem to be having any problems with mental deficits."

No one suggests that eating large amounts of mercury is a good idea. But as NRDC's Solomon notes, there are also plenty of low-mercury seafood options. (See the chart for more information on species that pack the most omega-3s and the least mercury.)

No matter what kind of seafood you choose, skip anything deep-fried. According to the U.S. Department of Agriculture's Nutrient Database, breaded, fried shrimp -- as well as other similarly prepared seafood -- has few or no omega-3 fatty acids. (Find more details in the sidebar at right.) And depending on the oil used to prepare it, these foods could also come laden with unhealthy saturated and trans fats, both known to increase risk of heart disease. Nutritionally speaking, not a good catch. ·

Share fish tales with Sally Squires during the Lean Plate Club Web chat from 1 p.m. to 2 p.m. today athttp://www.washingtonpost.com. Find more fish resources as well as healthy recipes for seafood athttp://www.leanplateclub.com, where you can also subscribe to the free, weekly Lean Plate Club e-mail newsletter. Or e-mail Squires atleanplateclub@washpost.com.