Prospective studies on diet and coronary heart disease : the role of fatty acids, B-vitamins and arginine

In this thesis, the results of prospective studies on fatty acids, B-vitamins and arginine and the occurrence of coronary heart disease have been described. The results presented are mainly based on the Zutphen Elderly Study. In this study of 939 men aged 64-84 years, detailed information was available on dietary intake, biological risk factors, incidence of major chronic diseases, vital status and causes of death between 1985 and 1995. In addition, data of 5 cohorts from Finland, Italy and the Netherlands, and of all 16 cohorts of the Seven Countries Study were used to investigate specific hypotheses on diet-heart relations in an international setting. Using repeatedly collected data of serum cholesterol, dietary and lifestyle factors in the Zutphen Elderly Study, we observed that changes in intake of saturated fat, polyunsaturated fat, dietary cholesterol and alcohol, and changes in weight were significantly related to changes in total and/or HDL cholesterol concentrations. The strengths of the observed associations are comparable to those obtained in experimental studies performed in younger populations. This indicates that public health strategies on dietary interventions and weight reduction in order to improve cholesterol concentrations are relevant also at old age. The average trans fatty acid intake decreased 2.4% of energy in the Zutphen Elderly Study between 1985 and 1995, mainly due to industrial lowering of the trans fatty acid content in edible fats. Such a decrease in trans fatty acids intake is compatible with a 23% reduction in risk of coronary heart disease. Changes in food composition with respect to the trans fatty acid content are therefore important from a public health perspective. Using the Finnish, Italian and Dutch data of the Seven Countries study, fatty fish consumption was estimated to reduce the relative risk of coronary heart disease mortality with 34%. For total or lean fish consumption no effect was observed. People at risk for coronary heart disease are therefore advised to eat fish, preferably fatty fish at least once a week, to reduce their risk for coronary heart disease. We did not find evidence for a protective effect of intake ofα-linolenic acid on coronary heart disease incidence in the Zutphen Elderly Study. However, the strong association between the intake ofα-linolenic acid and trans fatty acids complicated studying this relationship. Of the B-vitamins, only the intake of folate and vitamin B6 were independently inversely associated with homocysteine in the Zutphen Elderly Study. In this cohort, intake of different B-vitamins did not protect against coronary heart disease, although there is a suggestion for a protective effect of vitamin B2. Arginine intake was not associated with the risk of coronary heart disease mortality, neither in the Seven Countries Study, nor in the Zutphen Elderly Study. Results of prospective and intervention studies are needed before definite statements can be made about the potential protective effect on coronary heart disease of B-vitamins, arginine andα-linolenic acid.