High doses of vitamin C may lower blood pressure

Supplementation with vitamin C may moderately reduce blood pressure, with even greater benefits for people with hypertension, says a new data analysis from the US.

The meta-analysis included 29 randomized controlled trials assessing a potential association between vitamin C intake and blood pressure, with a median trial duration of eight weeks (1). The analysis showed that taking an average of 500 milligrams of vitamin C daily (about five times the recommended daily requirement) reduced systolic and diastolic blood pressure by 3.84 and 1.48 millimeters of mercury in the short term. Among those diagnosed with hypertension, the drop was nearly 5 millimeters of mercury.

The researchers commented that although the findings show significant blood pressure-lowering effects with vitamin C supplementation, large long-term trials would have to confirm the results before vitamin C supplementation can be recommended for the prevention of hypertension or as adjuvant antihypertensive therapy. By comparison, patients who take blood pressure medication, such as ACE inhibitors or diuretics, can expect a roughly 10 millimeter of mercury reduction in blood pressure. Vitamin C may act as a diuretic, causing the kidneys to remove more sodium and water from the body, which helps to relax the blood vessel walls, thereby lowering blood pressure.

According to the most recent data from the American Heart Association, about 33.5% of adults in the US have hypertension, a leading cause of cardiovascular disease, which account for about 35% of deaths in the US annually.

1. Juraschek S. P. et al. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition. Published online April 2012.