Is “The Japan Diet” Cardioprotective?

Lifestyle modifications such as diet change and exercise therapy are recommended as first-line therapy for risk factors for atherosclerotic cardiovascular diseases (ASCVD). Ancel Keys et al., in their landmark epidemiological study, the Seven Countries Study, which started in 1958 1) , reported that a high serum cholesterol level is a risk factor for coronary artery diseases (CAD) and that a high intake of dietary cholesterol and saturated fatty acids leads to a high serum cholesterol level. At that time, the incidence of CAD in Japan was the lowest among the seven countries, indicating that the Jap-anese diet was cardioprotective. However, there was remarkable economic development in Japan after World War II, and the associated urbanization caused marked changes in the living environment, i.e., west-ernization of lifestyle, which led to an increase in the obese, dyslipidemic, and diabetic populations. Hyper-tension also changed from the salt-dependent type to hypertension accompanied by metabolic abnormalities , consequently, with marked changes in the pathology of stroke, i.e., from cerebral bleeding and the lacuna type to atherothrombotic cerebral infarction. Such changes in risk factors for ASCVD have led to an epidemiological transition in Japan. However, to date, the incidence of CAD in Japan remains less than half of that in the U.S. 2) In the ERA-JUMP study 3) , which was a post-World War II cohort study on Japa-nese men and white men in the U.S., Sekikawa et al. reported that serum n-3 fatty acid levels were much higher among Japanese than among Americans and that the incidences of both carotid intima media thickness and coronary artery calcification were more reduced among Japanese than among Americans, even though lifetime cholesterol levels and blood pressures were similar between Japanese and Americans. The authors concluded that a high intake of n-3 fatty acids has anti-atherosclerotic effects. In another epidemiological study, JPHC 4) , the incidence of total CAD was 1/3 in people who had a very high intake of fish compared with those who had a very low intake. However, other epidemiological studies such as JACC 5) did not observe significant differences in the incidence of CAD between people with a high and those with a low fish intake. A recent RCT conducted in Japan, the Japan EPA Lipid Intervention Study (JELIS) 6) , found that the incidence of CAD was significantly lower in patients treated with a combination of statin and n-3 fatty acids than those treated …