Good Fish, Bad Fish

Oil is good for the heart, but mercury negates benefits

To measure the impact of regular fish consumption on heart health, researchers measured levels of omega-3 fatty acids from fish in participants' blood and then they also measured the mercury levels in the hair. There were just over 1,800 randomly selected middle-aged Finnish men. In a report published in the journal of the American Heart Association, Circulation, researchers found that higher fatty acid levels in the blood, associated with eating more fish, appeared to help protect men from future heart attacks. Men with the highest serum levels of docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) had a 44% lower risk of suffering an acute coronary event compared to men with the lowest levels.

"This association was strong and independent of other risk factors," the authors noted. Higher DPA and DHA levels were also linked with increased "good" cholesterol (HDL), lower insulin levels, and reduced tendency for blood to clot.
But this was only part of the story. Fish is also known to be one of the biggest food sources of mercury, a toxin linked to cholesterol oxidation and increased risk of heart attack. The amount of mercury inside each man's body strongly influenced the degree of cardiovascular benefit he derived from the omega-3 fatty acids in fish.

Men with blood DPA and DHA levels in the highest fifth of the group and in the lowest two-thirds of the group with the lowest hair mercury levels had the lowest overall risk of an acute coronary event. Their risk was an astounding 67% lower than men who fell within the highest third of mercury levels and the lowest fifth of DPA and DHA.

These results may explain why studies examining the impact of fish consumption on cardiovascular health sometimes contradict one another. Increasing levels of Omega 3 fatty acids clearly reduces cardiac risk, but long-term accumulation of mercury could offset these gains and could even negate the protective influence.

Editors note: have a serving of sea vegetables with your salmon and you may end up with less mercury in your system. Sea vegetables and supplements of Chlorella are known to reduce mercury.

And in a related story . . .
Shark bites, and holy (heavy metal) mackerel Pregnant women need to avoid eating certain types of fish. Pregnant women should not eat shark, swordfish, king mackerel or tilefish because they may contain enough mercury to damage the fetus's nervous system, the U.S. Food and Drug Administration announced. The agency warned that young children, nursing mothers and women who may become pregnant should also avoid those fish (Consumer groups wanted fresh tuna, used in sushi or served as tuna steak, added to the warning list as well.)
A National Academy of Sciences report estimated up to 60,000 children a year were born each year who had been exposed to during pregnancy to levels of mercury that could interfere with development of the brain and nervous system.

Even so, seafood, a naturally low-fat source of protein, can be an important part of a balanced diet for pregnant women and women who may become pregnant, FDA said."You can safely eat 12 ounces per week of cooked fish," the FDA advisory said."You can choose shellfish, canned fish, smaller ocean fish or farm-raised fish--just pick a variety of different species." Mercury enters the environment naturally and through industrial pollution. Nearly all fish contain trace amounts of methyl mercury but longer-lived, larger fish that feed on other fish, like shark or swordfish, accumulate the highest amounts of methyl mercury and pose the largest threat to people who eat them regularly.
In a related announcement, the Environmental Protection Agency said pregnant women, women who might become pregnant, nursing mothers and young children should eat only one meal per week of freshwater fish caught by family members or friends. EPA advises consumers to check with their state or local health departments for specific advice about fish from local waters.

*These statements have not been evaluated by the Food and Drug Administration.

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