PITTSBURGH, PENNSYLVANIA. It is a well-established fact that Japanese men have far less coronary artery disease than do American men. A recent, large autopsy-based study concluded that raised lesions in the coronary arteries (a sign of atherosclerosis) were far more common among White men in the US (50% had such lesions) than among Japanese men (15% had such lesions) in the age group 30-34 years. An obvious conclusion would be that this is likely due to genetic differences, but is it? An extensive team of scientists from the US (Universities of Pittsburgh and Honolulu) and Japan (University of Medical Science) set out to answer this question.
Their study included 281 Japanese men (born and living in Japan), 306 White Americans (born and living in the US), and 281 Japanese-American men who were 3rd or 4th generation living in Hawaii. The average age of the participants was 45 years (range of 40 to 49 years). Somewhat surprisingly, Japanese men had less favorable or similar risk profiles in regard to hypertension, LDL cholesterol, triglycerides, diabetes and cigarette smoking when compared to White American men. Japanese men were, however, significantly less likely to be obese than American and Japanese-American men. All study participants had blood samples taken, had their intima-media thickness (IMT) of their carotid artery measured, and underwent electron beam computed tomography to measure their degree of coronary artery calcification (CAC).
Japanese men had substantially less CAC (9.3%) than did American (26.1%) and Japanese-American men (31.4%). They also showed substantially less plaque formation in the carotid artery (0%) than did American men (0.7%) and Japanese-American men (16.7%). These findings pretty well demolish the hypothesis that the lower level of atherosclerosis in Japanese men is a genetic trait. So what does account for the lower level of atherosclerosis?
After considering the results of the blood tests, the research team concluded that it is the high serum level of EPA and DHA (eicosapentaenoic acid and docosahexaenoic acid, respectfully), the main components of fish oils, that provides the protection against atherosclerosis. While there was no significant difference in total fatty acid content between the three groups, there was a very marked difference in the percentage of these fatty acids constituted by EPA and DHA. In Japanese men the EPA and DHA percentage was 8.4% versus 3.2% in American men and 4.2% in Japanese- American men. Furthermore, the researchers also noted a direct inverse relationship (in Japanese men only) between serum levels of EPA and DHA and extent of coronary and carotid artery calcification. They conclude that the habitual consumption of large amounts of fish protects against atherosclerosis and urge large-scale trials to ascertain whether a vastly increased intake of fish oil among American men would similarly protect them against atherosclerosis and coronary artery disease.
Seikikawa, A, et al. Marine-derived n-3 fatty acids and atherosclerosis in Japanese, Japanese-American, and White men. Journal of the American College of Cardiology, Vol. 52, No. 6, August 5, 2008, pp. 417-24