Objective: To assess the relationship of biological markers of dietary factors with blood pressure (BP) (Core Study) and with age-adjusted mortality rates of stroke and ischemic heart disease (Complete Study) in the WHO Cardiovascular Diseases and Alimentary Comparison (CARDIAC) Study, a multicentre epidemiological study in 55 centres of 24 countries as of 1993.
Design and methods: From each population, 100 men and 100 women aged 48 to 56 years were randomly selected for BP measurement, 24-hour urine collection, blood tests, etc. Various biological dietary markers from the urine and blood were analysed centrally. Age-adjusted mortality rates from stroke and ischemic heart disease were obtained from 19 centres in 14 countries.
Results: Core Study: Cross-centre analyses, using simple linear regression, showed a positive relationship of body mass index to systolic BP and diastolic BP in men (p < 0.001) and women (p < 0.05). There were also strong positive correlations between 24-hour sodium excretion rates and both systolic and diastolic BP (both p < 0.01) in men. An inverse relationship was found between the 24-hour magnesium/creatinine excretion ratio and diastolic BP (p < 0.05) in men. Complete Study: Stroke mortality was significantly positively related to the 24-hour sodium excretion rate in men (p < 0.01) and to the sodium/potassium ratio in both sexes (p < 0.05). It showed an inverse relationship of serum phospholipid with serum total cholesterol (p < 0.05) and a positive relationship with arachidonic acid. A strong positive relationship between serum cholesterol level and ischemic heart disease (p < 0.001) was observed in men. The serum phospholipid n-3 polyunsaturated fatty acid (PUFA) level and the PUFA to saturated fatty acid (SFA) ratio were significantly inversely correlated with ischemic heart disease. The 24-hour taurine excretion rate, a biological marker of seafood protein intake, showed a significant inverse correlation with ischemic heart disease in both sexes (p < 0.01).
Conclusion: The Core Study revealed a consistent adverse effect of high body mass index and excess salt intake on BP and a beneficial effect of magnesium on BP. The Complete Study demonstrated an adverse effect of high sodium, low potassium intake and hypercholesterolemia on stroke; and an adverse effect of cholesterolemia as well as beneficial effects of serum phospholipid n-3 PUFA, PUFA/SFA and the taurine excretion rate on death from ischemic heart disease.