FRIDAY, Sept. 19, 2008 (HealthDay News) -- Vitamin C may help lower high blood pressure by calming an overactive central nervous system, new Italian research suggests.
Using intravenously delivered vitamin C, "our study demonstrated for the first time in humans that we can reduce sympathetic nervous system overactivity, and consequently blood pressure, (by) targeting oxidative stress," said study lead author Dr. Rosa Maria Bruno from the University of Pisa.
Bruno explained that the sympathetic nervous system (SNS) is part of the body's central nervous system that controls non-voluntary activities, such as blood pressure. Overactivation of the system has been identified as an underlying foundation for the onset of elevated blood pressure and resulting organ damage.
The Italian team was expected to report its findings Friday in Atlanta at the American Heart Association's Conference of the Council for High Blood Pressure Research.
The study builds on prior research touting the potential of vitamin C and other antioxidant nutrients to lower high blood pressure. For example, this past January, British authors presented evidence in The American Journal of Clinical Nutrition that suggested that having high levels of vitamin C in the blood might help reduce stroke risk.
In the current work, Bruno and her colleagues focused on 12 patients diagnosed with an "essential" form of high blood pressure -- namely, one with no known cause.
None of the patients had received any kind of prior treatment for their condition. Over a five-minute period, all the patients were intravenously administered three grams of vitamin C, after which they were monitored for 20 minutes to assess blood pressure and SNS activity. Electrocardiograms were also taken.
The researchers found that "antioxidant capacity" went up as a result of the IV infusions, while SNS activity dropped by about 11 percent.
In addition, the participants' blood pressure was found to have plunged nearly 7 percent on average, with a specific drop in diastolic blood pressure (the bottom number on a reading) of 9 percent. However, no significant drop in systolic blood pressure was observed.
But Bruno said it's too early to say that vitamin C can reduce either blood pressure or sympathetic activity among healthy patients -- just among those with high blood pressure.
"(And) our results cannot be directly translated into clinical practice, because to obtain this result, we used one high dose of vitamin C administrated intravenously," she added. "We don't know if chronic oral administration of vitamin C can achieve the same effect."
Dr. Suzanne Steinbaum, director of Women and Heart Disease at Lenox Hill Hospital's Heart and Vascular Institute in New York City, added a similar caveat.
"What's interesting about this particular trial is that the vitamin C was given intravenously," she noted. "And maybe that's why it worked here. It's really hard to know. Yet there's something to be said about the concept of vitamin supplementation in treating vascular disease because of the antioxidant content. It makes sense physiologically."
"However, although it would be nice to say to someone, 'if you eat right and take these vitamins, you're going to be OK,' rather than 'here -- take all these medications, with all these side effects,' this is a small esoteric study," Steinbaum said. "This finding is certainly not going to make me or anyone else run out and start giving vitamin C intravenously to our patients."
For additional information on lowering blood pressure, visit the U.S. National Heart, Lung, and Blood Institute.