Study Shows Vitamin C Lowers Blood Pressure
Dec. 10, 1999 (Indianapolis) -- Studies have shown that increased dietary
intake of vitamin C is related to lower blood pressure (BP) readings. A new
study in the Dec. 11 issue of the journal The Lancet shows similar
"We are interested in the effects of vitamin C on coronary heart
disease," says author Joseph A. Vita, MD, who is associate professor of
medicine at the Boston University School of Medicine, in an interview with
WebMD. "We published another study earlier this year that observed some
beneficial effects, including dilation of the blood vessels, in people taking
vitamin C. We were also intrigued by the literature that suggests the amount of
vitamin C in the diet actually influences blood pressure, with the more vitamin
consumed, the lower the blood pressure."
Forty-five otherwise healthy patients with a history of high blood pressure
were enrolled in the study. Following a 2 g dose of vitamin C on the first
visit, they were given either placebo or 500 mg a day of vitamin C. Medications
to treat high BP were withheld for either 12 or 24 hours prior to two visits,
one month apart. Otherwise, regular medications were continued through the time
period. Patients were told to fast overnight and not smoke for 24 hours prior
to the visits.
Systolic BPs (the higher number) in the two groups were similar in the
beginning and at two hours after the initial dose. Following one month of
vitamin C use, average systolic pressure had fallen for the subjects who were
taking the vitamin C, whereas the placebo had no effect. Vitamin C
concentrations in the blood were similar at the beginning of the study between
the two groups and increased in the vitamin C group at both two hours and one
month. There was an inverse correlation between the change in average BP and
the change in vitamin C concentrations. This means that as the amount of
vitamin C in the blood goes up, the person's BP goes down.
"Vitamin C is a safe medicine with almost no known side effects,"
says Vita. "This is potentially a new treatment that people with high blood
pressure might add under the direction of their doctor. Since we do yet know if
this effect can be sustained for periods longer than 30 days, I certainly would
not want any patients to stop taking their blood pressure medicines based on
William G. Haynes, MD, assistant professor of internal medicine at the
University of Iowa, says in an interview with WebMD that while BP was reduced,
other major concerns in hypertension care, such as impact on the risk of death
or stroke, were not measured. He also is concerned about how little is known
about the long-term consequences of taking vitamin C at levels several times
the adult recommended daily requirement.
"They are giving doses that are much higher than the recommended daily
requirement of vitamin C and more than eight times that seen in a standard
multivitamin," says Haynes, who was asked to give an independent view of
the study. "We just don't know yet what the side effects might be at that
- A new study shows that taking vitamin C supplements, in the form of
ascorbic acid, can lower blood pressure.
- The trial lasted only 30 days, so it is unknown whether vitamin C could be
an effective long-term treatment.
- One criticism of the study is that the dose of vitamin C used to lower
blood pressure is several times the recommended daily allowance, so side
effects at that level are not known.