Effect of vitamin C on ambulatory blood pressure and plasma lipids in older persons

Objectives To determine the effect of oral vitamin C supplements on ambulat ory blood pressure and plasma lipids. Design A 6-month doubts-blind randomized placebo-controlled cross-over stud y with a 1-week washout between cross-over periods. Methods Vitamin C 500 mg daily or matching placebo was given to 40 men and women aged between 60 and 80 years for 3 months each in a cross-over fashio n, Clinic and 24-h ambulatory blood pressure, plasma ascorbate and lipids w ere measured at baseline and at the end of each cross-over phase. Results Clinic blood pressure did not change between placebo and Vitamin C phases. Daytime ambulatory blood pressure showed a small but significant fa il in systolic blood pressure (2.0 +/- 5.2 mmHg; 95% confidence interval 0- 3.9 mmHg) but not in diastolic blood pressure. Regression analysis showed t hat with increasing baseline daytime blood pressure the fall in blood press ure with vitamin C supplementation increased. Regression analysis of the ch ange in high-density lipoprotein (HDL) cholesterol showed a significant eff ect of sex on the change in HDL cholesterol. In women, but not men, HDL cho lesterol increased significantly by 0.08 +/- 0.11 mmol/l, P = 0.007. There was no change in low-density lipoprotein cholesterol between treatment peri ods. Conclusion In older adults high intakes of ascorbic acid have modest effect s on lowering high systolic blood pressure, which could contribute to the r eported association between higher vitamin C intake and lower risk of cardi ovascular disease and stroke. J Hypertens 2000, 18:411-415 (C) Lippincott W illiams & Wilkins.