Increasing vitamin C levels may have a favorable effect on blood pressure. Research published in the American Journal of Clinical Nutrition (1993;57:213–217) found that serum vitamin C levels were inversely related to blood pressure. In other words, higher blood concentrations of vitamin C were associated with a lower likelihood of having high blood pressure. The study also noted that smokers had significantly lower vitamin C levels than non-smokers.
An article in the Journal of Hypertension (1991;9[11]:1076–1077) reported that several epidemiologic studies have demonstrated an inverse relationship between vitamin C intake and blood pressure. The authors noted that vitamin C supplementation had been shown to lower blood pressure in some individuals with borderline hypertension.
Additional insight comes from a small study published in Nutrition Research (2007;27[2]:119–123), which examined the effects of vitamin C and garlic supplementation on blood pressure. The study included six subjects with mildly elevated blood pressure (approximately 140/90 mm Hg). Participants were treated in alternating ten-day periods, separated by one-week washout intervals, during which they received placebo, vitamin C alone (2,000 mg/day), garlic alone, or a combination of garlic and vitamin C.
In this study, garlic supplementation lowered systolic blood pressure but had no effect on diastolic pressure. Vitamin C alone did not significantly affect blood pressure. However, the combination of garlic and vitamin C reduced both systolic and diastolic blood pressure, bringing readings into the normal range.
While the study was very small, the findings suggest that vitamin C may play a supportive role in blood pressure regulation, particularly when combined with other dietary factors.
