THE EFFECTS OF DIETARY-LIPID MODIFICATION ON BLOOD-PRESSURE, CARDIOVASCULAR REACTIVITY AND SYMPATHETIC ACTIVITY IN MAN

Objectives: To examine the effect of dietary lipid modification on 24-h ambulatory blood pressure, cardiovascular reactivity and sympathetic activity in man. Design: Twenty-four normal volunteers consumed either a high-fat or a low-fat diet for 2 weeks in an open, randomized, crossover study of duration 6 weeks. Diets were isocaloric and balanced for sodium and potassium content. Methods: Cardiovascular reactivity was assessed by measurement of blood pressure responses to incremental infusions of angiotensin II and noradrenaline, and to sympathetic reflex testing. Plasma noradrenaline spillover and clearance rates were estimated using [H-3]-noradrenaline infusion. Results: Total plasma cholesterol and low-density lipoprotein-cholesterol levels both fell significantly on the low-fat compared with the high-fat diet, as did heart rate and mean arterial pressure (recorded by 24-h ambulatory monitoring). These changes were accompanied by reductions in blood pressure responses to cold pressor testing and to noradrenaline infusion on the low-fat diet. Plasma noradrenaline spillover and clearance rates did not change. Post hoc analysis showed an association between oral contraceptive use and increased noradrenaline sensitivity on the high-fat diet among the females tested. Conclusion: Dietary fat intake alters heart rate, blood pressure and cardiovascular reactivity to noradrenaline in man without changes in basal noradrenaline metabolism.