A baseline examination of residents over 40 years of age in A-I district of Shibata City, Niigata Prefecture, Japan, was conducted in 1977, for the purpose of finding out probable relationships between dietary factors and stroke or coronary heart disease (CHD). Subjects were 999 males and 1360 females for a response rate of 85% and 93%, respectively. The dietary intake of sodium, potassium, calcium, iron, magnesium, zinc, and copper was assessed using a food frequency questionnaire that we developed, and the results were analyzed for relationships between the intake of various kinds of mineral and blood pressure in a cross-sectional study. A cohort study of dietary mineral intake and incidence of stroke and CHD was also performed over 15.5 years from July 1977 through December 1992.
Relationships between energy-adjusted mineral intake and blood pressure, showed an inverse relationship between blood pressure and potassium and magnesium. There were no significant relationships between stroke incidence and dietary mineral intakes in the cohort study. However, for ischemic heart disease (IHD : myocardial infarction + sudden death), increased intake of potassium, magnesium and iron appeared to be associated with lower IHD incidence. According to the multivariate analysis using Cox' proportional hazard model, cerebro-and cardio-vascular diseases were strongly associated with age and blood pressure. With regard to myocardial infarction incidence, copper intake as well as age and blood pressure somehow had a minor effect. The relationship of dietary minerals to the incidence of stroke and CHD appears to be an indirect relationship mediated by blood pressure.
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