There is increasing evidence that free radicals (reactive oxygen species) play a significant role in essential hypertension (high blood pressure). Now researchers at the Boston University School of Medicine report that daily supplementation with vitamin C (ascorbic acid) can significantly reduce blood pressure in people suffering from hypertension. Their randomized, placebo-controlled study involved 39 patients (average age of 49 years) 29 of whom were taking antihypertensive medication. The study participants had diastolic blood pressure between 90 and 110 mm Hg and did not suffer from diabetes, coronary artery disease or heart failure. They also did not take estrogens or antioxidants within one month of the start of the study. After fasting overnight the patients had their blood pressures (systolic, mean, and diastolic) measured and had urine and blood samples collected. The measurements were repeated two hours after receiving a 2-gram oral dose of ascorbic acid or placebo and again after 30 days of oral supplementation with 500 mg/day of ascorbic acid or placebo. The researchers found that blood pressures were similar at baseline and after the acute treatment (2-gram dose). At the end of the 30-day period, however, the average systolic pressure in the vitamin C group had decreased from 155 mm Hg to 142 mm Hg and the mean pressure had decreased from 110 to 100 mm Hg. No changes were observed in the placebo group. The average diastolic pressure in the vitamin C group also decreased, but the difference from the placebo group was not statistically significant. Blood plasma levels of ascorbic acid increased significantly in the vitamin C group during the study; from 50 micromol/L to 149 micromol/L two hours after ingesting the 2-gram dose and levelling out at 99 micromol/L at the end of the 30-day test period. The researchers conclude that oral supplementation with 500 mg/day of ascorbic acid is useful for blood pressure control in patients with high blood pressure.