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The number of deaths from coronary heart disease among Japanese men is less than half that of American men. Whether this effect is due to genetic, dietary or other factors has not been confirmed. In the first international study of its kind, published in the August 5, 2008, issue of Journal of the American College of Cardiology, University of Pittsburgh Graduate School of Public Health assistant professor of epidemiology Akira Sekikawa, MD, PhD, and colleagues evaluated data from 868 men aged 40 to 49 enrolled in the ERA JUMP (Electron-Beam Tomography, Risk Factor Assessment Among Japanese and U.S. Men in the Post-World War II Birth Cohort) Study. Two hundred eight-one of the current study’s subjects were from Japan; 306 were Caucasian men from Pennsylvania; and 281 were Japanese-American men living in Hawaii. Blood tests measured total fatty acids and the omega-3 fatty acids eicosapentaenoic, docosahexaenoic and docosapentaenoic acids which are commonly obtained by consuming fish. Ultrasound examination assessed carotid artery intima-medial thickness (IMT), which is used to evaluate atherosclerosis. Coronary artery calcification (CAC) in the heart’s arteries, which also identifies heart disease, was assessed via electron-beam CT scanner.

Dr Sekikawa’s team found that although total fatty acid levels were similar among all subjects, the percentage of fish-based omega-3 fatty acids was twice as high among Japanese men compared with Americans of both European and Japanese descent. Japanese men had significantly less atherosclerosis, as indicated by lower average intima-media thickness and coronary artery calcification. Among Japanese men, intima-media thickness values declined with rising omega-3 fatty acid levels, a phenomenon that was not observed in either American group.

“The death rate from coronary heart disease in Japan has always been puzzlingly low,” Dr Sekikawa observed. “Our study suggests that the very low rates of coronary heart disease among Japanese living in Japan may be due to their lifelong high consumption of fish. Our study clearly demonstrated that whites and Japanese-Americans have similar levels of atherosclerosis, which are much higher than in the Japanese in Japan. This indicates that much lower death rates from coronary heart disease in the Japanese in Japan is very unlikely due to genetic factors.”

“Our study suggests that very high levels of omega-3 fatty acids have strong properties that may help prevent the buildup of cholesterol in the arteries,” Dr Sekikawa stated. “Increasing fish intake to two times a week for healthy people is currently recommended in the U.S. Our study shows much higher intake of fish observed in the Japanese [approximately 3 ounces daily] may have strong anti-atherogenic effect.”

“While we don’t recommend Americans change their diets to eat fish at these quantities because of concerns about mercury levels in some fish, increasing intake of omega-3 fatty acids in the U.S. could have a very substantial impact on heart disease,” he added.