We have investigated the effect on blood pressure of treatment with vitamin C (an antioxidant and free radical scavenger) in patients with both systolic and essential hypertension. Following a 2-week run-in phase, two age- and sex-matched groups of untreated hypertensive subjects were randomised in a double-blind study to receive 6 weeks’ oral treatment with either vitamin C, 250 mg twice daily (n = 22; 8M/14F, mean age 73.7 ± 4.9 years) or placebo, one capsule twice daily (n = 26; 10M/16F, mean age 73.8 ± 5.3 years). Blood pressure was measured in the sitting position using a random zero sphygmomanometer on three occasions during the run-in phase, and again at 2, 4 and 6 weeks after commencing treatment. Venous blood samples for measurement of plasma ascorbic acid (AA) and lipid peroxides (LP) were measured in all subjects at baseline and at 4 and 6 weeks after the start of vitamin C or placebo treatment. During the study period, significant falls in both systolic (vitamin C group, mean change -10.3 (95% CI 0.7-20.0) mm Hg, p = 0.05) and diastolic (vitamin C group, mean change -5.9 (95% CI 0.2-11.5) mm Hg, p = 0.03; placebo group, mean change -4.7 (95% CI 0.3-9.1) mm Hg, p = 0.05) blood pressure occurred. However, no statistical difference between the effects of either treatment on blood pressure was observed. At baseline, AA concentrations were lower in the vitamin C-treated group compared with the placebo group (44.6 ± 2.4 vs. 57.7 ± 4.2 μmol/l, p < 0.05). At 6 weeks, AA concentrations were similar to baseline in the placebo group (50.8 ± 4.6 μmol/l) but were significantly higher than at baseline in the vitamin C-treated group (80.7 ± 7.5 μmol/lp < 0.001). At baseline, LP concentrations were similar in the vitamin C and placebo-treated groups (5.0 ± 1.0 vs. 3.6 ± 0.8 nmol/l, respectively). After 6 weeks’ treatment with vitamin C, LP concentrations fell significantly to 1.6 ± 0.4 nmol/l, but no significant change after placebo was observed (4.4 ± nmol/l). We conclude: (1) No significant fall in blood pressure occurred after 6 weeks’ treatment with vitamin C in comparison with placebo; (2) vitamin C treatment is associated with a marked antioxidant action but further studies are required to relate whether this action is relevant to any hypotensive action of this vitamin; (3) the small fall in systolic blood pressure after vitamin C may have wider implications in population-based studies in reducing stroke incidence in elderly patients and suggests the need for large long-term studies to be established.

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