A new study has revealed that intake vitamin C in large doses may moderately reduce blood pressure.
However, the researchers from Johns Hopkins University stopped short of suggesting people load up on supplements.
"Our research suggests a modest blood pressure lowering effect with vitamin C supplementation, but before we can recommend supplements as a treatment for high blood pressure, we really need more research to understand the implications of taking them," Edgar "Pete" R. Miller III, the study leader, said.
Roughly 30 percent of adults in the United States have high blood pressure, or hypertension, an important risk factor for heart disease and stroke. Successful treatment may include drugs, exercise, weight loss, and dietary changes such as reducing salt intake.
Some experts believe that large amounts of vitamin C, an essential micronutrient found primarily in fruits and vegetables, could lower pressure as well, but randomized, controlled dietary intervention studies - the gold standard of nutrition research - have produced mixed results.
Miller and his colleagues reviewed and analyzed data from 29 randomized, controlled, previously published clinical trials that reported systolic and/or diastolic blood pressure values and also compared vitamin C intake to a placebo.
What they found is that taking an average of 500 milligrams of vitamin C daily - about five times the recommended daily requirement - reduced blood pressure by 3.84 millimeters of mercury in the short term. Among those diagnosed with hypertension, the drop was nearly 5 millimeters of mercury.
By comparison, Miller said, patients who take blood pressure medication such as ACE inhibitors or diuretics can expect a roughly 10 millimeter of mercury reduction in blood pressure.
500 milligrams of vitamin C is the amount in about six cups of orange juice. The recommended daily intake of vitamin C for adults is 90 milligrams.
"Although our review found only a moderate impact on blood pressure, if the entire U.S. population lowered blood pressure by 3 milliliters of mercury, there would be a lot fewer strokes," Miller said.
The study has been published in the American Journal of Clinical Nutrition.