The importance of high blood pressure as a major risk factor for cardiovascular diseases (CVD) has led to extensive research in the etiology of hypertension. Regulation of blood pressure (BP) in humans involves many different organs and physiological processes that contribute either directly to the determination of BP level or indirectly by modifying the response. A large number of nutritional factors may have an influence on normal cardiovascular physiology, and many of them may also be important in the pathophysiology of hypertension (35, 37, 39). Because of the interactions among different nutrients, the importance of the contribution of a single nutrient to BP regulation is difficult to define precisely. Moreover, it is unlikely that modification in the intake of a single such nutrient would result in a universal effect on BP in all persons of all populations. The nutrient interactions mentioned above occur not only in terms of physiological events, but also in terms of diet composition and selection and nutrient absorption, bioavailability, and ultimate elimination (35). This complexity poses serious problems for the design of studies that attempt to confirm causative links between various nutrients and BP. Unfortunately, these problems have too often been ignored or overlooked in study design and in interpretation of results. As in any other type of etiological study, a clear distinction should be made between determinants (i.e., characteristics on which the BP level depends), modifiers (i.e., subject characteristics on which measurements of the relation between BP and its determinants depend), and confounding factors (i.e., predictors of BP that differ among the compared categories of the determinant). The availability of effective antihypertensive agents and the encouraging results of several well-conducted clinical trials studying the effectiveness of lowering high BP to prevent cardiovascular complications (19, 30, 65) have accelerated a move toward active drug therapy. Recent epidemiological studies have, however, clearly shown that, although significant reductions in BP levels were achieved in the 197Os, the situation is still far from adequate (23, 62). In Finland, for instance, about 40% of the hypertensive population is not adequately controlled, according