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Controversy Over Fish Oil Supplements and Sudden Death RiskDaily supplements of a fatty acid found in fish oil cuts the risk of sudden death by half in people who have had heart attacks. Despite this finding from a new Italian study, the American Heart Association says it cannot yet recommend these supplements. Even more discouraging, another expert says many cardiologists are not telling patients about this benefit and drug companies are studiously avoiding the subject. The report comes from a study that enrolled more than 11,000 Italians who survived heart attacks. They all got the usual medical treatment and lifestyle advice. In addition, some took 1 gram a day of a supplement containing n-3 polyunsaturated fatty acids (PUFA), also known as omega-3 fatty acids, the kind found in fish oil. Others took a vitamin E supplement, still others took both, and a control group took neither. After three months, says a report in the journal Circulation, there was a significant difference in the incidence of sudden death—0.5 percent for those taking the PUFA supplement, 0.7 percent for those who did not. The difference persisted after 42 months—a 2 percent risk of sudden death for those taking PUFA, 2.7 percent risk for those who did not. The overall death rate was 8.4 percent for PUFA people, 9.8 percent for the others—again, statistically significant. "At the end of the study, we realized that there was a significant reduction of total mortality, whereas the reduction of all cardiovascular events was not statistically significant," says Dr. Roberto Marchioli, leader of the study. The risk of sudden death is highest in the months after a heart attack, Marchioli notes, which is exactly when the fish oil supplement benefit is clearest. That benefit is not related to cholesterol levels or a reduction in blood clots, he says. "It seems to support the idea that the mechanism of action of the fatty acids is a reduction in arrhythmias," Marchioli says. The current theory is PUFA helps keep the heartbeat normal by regulating the electrical activity of heart muscle cells. "We know the molecular mechanism by which these fatty acids stabilize the heart electrically," says Dr. Alexander Leaf, professor of clinical medicine at Harvard Medical School and author of an accompanying editorial. Work in his laboratory has shown PUFA makes heart cells resistant to arrhythmias. The finding needs confirmation, Marchioli says, and Leaf agrees that "we need a few more careful clinical trials of people at risk of sudden death." The American Heart Association says it does not recommend fish oil supplements and will not recommend them "until there is compelling evidence that they benefit overall cardiovascular health." The organization does, however, recommend eating plenty of fish. That's all well and good, says Marchioli, but "not all people like fish, and in addition it is rather difficult to eat fatty fish every day of one's life." A Tuna Sandwich a Day Keeps Heart Problems at Bay?Two additional studies affirm the beneficial value of fish in the diet in preventing the kind of blockage of arteries that leads to heart attacks and to strokes. In fact, the recommendation is if you want to reduce your risk of a heart attack by more than 20 percent, just eat a tuna fish sandwich not once a day, but once a month. And while both studies come from Boston, "the land of the bean and the cod," cod is not high on the list of the best fish to eat. That's because the benefit comes from the omega-3 fatty acids, also called polyunsaturated fatty acids (PUFAs), says Dr. JoAnn E. Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital and a co-author of the study that appears in a recent issue of the Journal of the American Association (JAMA). While eating cod is not a bad idea, fish that are especially rich in PUFAs are mackerel, salmon, sardines—and tuna, Manson says. Researchers have long noticed that groups of people who eat lots of fish have a lower death rate from heart disease; in Alaska, it's known as the "Eskimo paradox." The findings, based on analysis of the 16-year Nurses Health Study of nearly 85,000 women, found a neat relationship between fish intake and the risk of heart disease and death. Women who ate fish one to three times a month reduced that risk by 21 percent, compared to those who had less than one serving of fish each month. The risk is lower progressively as fish intake increases, with a reduction of 34 percent for more than five fish meals a week, but the significant reduction can come from just that one tuna sandwich a month, Manson says. "There appear to be three mechanisms by which the long-chain, omega-3 fatty acids act," Manson says. "One, there is a favorable effect on blood cholesterol. Two, there is a lowering of the tendency for blood clots. Three, there is also an effect on heart rhythm, a reduction in harmful arrhythmias." The study does break some new ground, Manson says, because it is "the first large-scale study of fish intake and the risk of heart disease in women. The risk has been studied primarily in men, but the findings apply to both sexes." The newest report on men, also from Brigham and Women's Hospital, concerns the Physicians' Health Study, which has followed 22,000 male physicians for more than 17 years. It looked at blood levels of PUFAs and found them "strongly associated with a reduced risk of sudden death among men without evidence of prior cardiovascular disease." That study appeared in the April 11 issue of the New England Journal of Medicine, and was released a day early to coincide with the Nurses Health Study report. Both studies come on the heels of the Italian report (above) saying that daily supplements of PUFAs cut the risk of sudden death by half. Right now, the American Heart Association says it is best to get PUFAs from fish, rather than supplements. Both American studies and the one from Italy (above) will be considered when the AHA's nutrition committee meets next week, says Dr. Alice H. Lichtenstein, professor of nutrition at Tufts University and vice chairwoman of the committee. It is not possible to predict what the committee will decide, and any change in recommendations probably will not come quickly, she says. "We will reconsider the position," Lichtenstein says. "Prior to this, there has not been enough data to make a recommendation on fish oil supplements. Now we have to go back and look at the new data." Always consult your physician regarding what is recommended for your individual health. |
May 2002Controversy Over Fish Oil Supplements and Sudden Death Risk A Tuna Sandwich a Day Keeps Heart Problems at Bay? Eating More Fish Cuts Preterm Delivery Risk In a Related Story ...Eating More Fish Cuts Preterm Delivery RiskIf you have just found out that you are pregnant, one of the best things you might do for your baby is have a tuna fish sandwich. Or cod, or scrod, or some other fish dish. A Danish study finds that low intake of fish during pregnancy is associated with a higher risk of premature delivery and low birthweight—both major problems for newborns. The study, which included more than 8,700 pregnant women, is "the largest ever done," says Sjurour F. Olsen, a senior scientist in the Danish Epidemiology Science Center in Copenhagen, lead author of a report in the Feb. 23 issue of the British Medical Journal. It does not take a lot of fish in the diet to reduce the risk, Olsen says—one meal a week will produce the protective effect. The risk of premature delivery and low birthweight was directly related to fish intake, the study finds. It happened for 7.1 percent of the women who never ate fish and for only 1.9 percent of those who ate fish at least once a week. The reason is not entirely clear, but it probably is related to the omega-3 fatty acids found in fish, Olsen says. Those chemicals are poly-unsaturated fatty acids that play a role in the body's production of prostaglandins, which in turn play a role in the widening of the cervix that initiates childbirth, he says. It is too early to recommend that women eat a lot of fish or take fish oil supplements during pregnancy, says Dr. Michael Katz, vice president for research at the March of Dimes Birth Defects Foundation. "One of the worst possible outcomes is that people get hooked on data and go overboard," he says. While "there is no harm in eating fish," Katz says, the real story on its value during pregnancy will come from a study that has begun in China, in a region where fish-eating is not common. Pregnant women are being given fish oil and olive oil, and the outcomes of their pregnancies will be recorded. Results are not expected for a while, Katz says. Showing a beneficial effect of eating fish during pregnancy is "an exciting possibility," Katz adds. "But whether it is real will have to be determined by the prospective study." "There are certain things we do know," Katz says. "A woman should start taking folic acid before she gets pregnant, to prevent neural tube defects. She shouldn't smoke and shouldn't drink during pregnancy. And she should be sure there is good health care supervision for a proper diet, exercise and so on." Always consult your physician for more information. Online Resources:(Our Organization is not responsible for the content of Internet sites.) Circulation, Journal of the American Heart Association |