By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

It has been found in epidemiological studies that people who consume diets that contain a lot of vitamin C (also known as ascorbic acid) tend to have lower blood pressure, and the DASH diet, which has been shown to be so effective at lowering blood pressure, includes several servings of fruit, which is the major source of vitamin C in the diet. A number of studies (some of which we have reviewed) have looked to see whether taking vitamin C pills lowers the blood pressure, with inconclusive results.

A new study conducted in Boston has examined the effects of giving hypertensive patients 500 milligrams a day of vitamin C. There were 39 patients altogether, half of whom got vitamin C and the other half matching placebo (inert pills); their average blood pressure before the study was 155/88 mmHg. Blood pressure was measured two hours after giving the first dose and after one month of treatment. The study was double blind, so that no one knew what type of pill each patient was getting until after the study. The results were clear- cut. There was no effect on blood pressure two hours after the first dose, but after one month, the systolic pressure in the group getting the vitamin had fallen by 12 mm Hg more than those getting the placebo. The effect on diastolic pressure was less pronounced and did not reach statistical significance.

Doctor’s comments

Other studies of the effects of vitamin C on blood pressure have given less consistent results, but in this one, the effects on systolic pressure were quite strong. The reason why the change of diastolic pressure was less pronounced may have been because it was normal to begin with. The mechanism by which vitamin C lowers pressure is not known, but it is an antioxidant, and it may help to restore the function of the endothelium (the inner lining) of the arteries, which becomes disrupted in hypertension, in part because of the effects of oxidation by free radicals.

Where it was published