Nutritional interventions and blood pressure : role of specific micronutrients and other food components

Background Elevated blood pressure is an important risk factor for cardiovascular diseases (CVD). Modest reductions in blood pressure at the population level, as can be achieved by dietary and lifestyle changes, have a large impact on the burden of CVD. Blood pressure is regulated by several physiological mechanisms, including vascular endothelial function. This thesis The studies described in this thesis examined the potential effects of various micronutrients and other food components on blood pressure and endothelial function. The first aim was to assess the importance of selected minerals on population blood pressure levels and the second was to investigate the vascular effects of food components other than minerals that have recently attracted attention in the field of nutrition and blood pressure. A review of 21 national surveys showed that current dietary potassium intakes are suboptimal (1.7-3.7 gram per day). We estimated that increasing intakes to the recommended level of 4.7 gram per day can reduce population systolic blood pressure by 2-3 mmHg in Western countries, this effect being similar to that which can be achieved by reducing current sodium intakes to recommended levels. Our meta-analysis of 40 randomized controlled intervention studies showed that increasing calcium intake by ~1200 mg per day significantly lowers systolic blood pressure by 2 mmHg and diastolic blood pressure by 1 mmHg. This effect tended to be stronger in populations with lower intakes (<800 mg per day). In an 8-week placebo controlled parallel study in 124 subjects with elevated blood pressure, we found no significant blood pressure lowering effects of skimmed milk enriched in potassium (1500 or 750 mg per daily serving) combined with calcium, magnesium, selenium, vitamin C and vitamin E. However, this study was not designed to detect reductions in systolic blood pressure of 2-3 mmHg, which are still relevant at the population level. In two 4-week placebo controlled cross-over studies, in 162 subjects with untreated elevated blood pressure, we could not demonstrate an antihypertensive effect of a yogurt drink with lactotripeptides obtained by enzymatic hydrolysis (study 1: 10.2 mg per day; study 2: 4.6 mg per day plus 350 mg added potassium). In another 2-week placebo controlled cross-over study in 35 healthy males we found no consistent effect on endothelial function and blood pressure of ~800 mg polyphenols per day from either a wine-grape mix or grape seeds. Finally, a meta-analysis of 14 randomized controlled intervention studies showed that folic acid at a high dose (≥5000 g per day), which can not be attained with a regular diet, significantly improved flow-mediated dilation by 8%. Conclusion Adequate potassium and calcium intakes can play an important role in the prevention of hypertension at the population level. Lactotripeptides have no relevant effect on blood pressure in Caucasian populations. The potential of grape polyphenols and folic acid to improve endothelial function is limited. Multiple actions are needed to lower blood pressure at the population level and reduce the burden of CVD. To improve intakes of potassium and calcium, public health measures should re-emphasize the intake of fruits, vegetables, and low-fat dairy products. Further optimization of mineral intakes, in particular reduction of sodium intake, requires collaborative actions of government and food industry.