By E.J. Mundell
SAN DIEGO, Mar 03 (Reuters Health) -- In a finding that contradicts previous
studies, researchers say vitamin C supplements may increase the risk of
atherosclerosis -- arterial disease that can cause heart attack or stroke.
The finding may only apply to vitamin C in pill form, however, since this
"was not demonstrated for vitamin C from food," according to study lead author
Dr. James H. Dwyer of the University of Southern California, Los Angeles. They
reported their findings at the American Heart Association's 40th Annual
Conference on Cardiovascular Disease Epidemiology and Prevention.
The researchers used high-resolution ultrasound to measure the thickness of
the wall of a neck artery in 573 healthy men aged 40 to 60 over a period of 18
months. The investigators used blood tests and interviews to determine each
man's level of vitamin C intake, either through diet or supplements.
The result? Men who took 500 milligrams of vitamin C daily had an increase
in arterial wall thickness (an indicator for atherosclerosis) that was 2.5 times
greater than men who did not use supplements, Dwyer said. At a press conference
following his presentation, he said the effect was more dramatic among smokers,
who "had a five-fold increase in the rate of thickening."
The results appeared to hold true regardless of whether or not the men
already showed signs of atherosclerosis at the beginning of the study.
Dwyer cautioned, however, that the data should be "treated as suggestive
only because this is just one study, and there may be confounding variables that
we have not uncovered."
Dr. Joseph Vita, a cardiac researcher at Boston University, agrees, noting
that "the overwhelming weight of evidence -- the other studies that have looked
at vitamin C -- have all suggested that it is favorable in terms of reducing
risks for heart disease." In fact, a recent study conducted by Vita and
colleagues found that vitamin C supplement use was associated with a decline in
angina -- chest pain that is often a warning sign of diseased coronary arteries.
Speaking with Reuters Health, Vita also pointed out that the UCLA study was
unable to rule out confounding factors that might have skewed the results. For
example, he speculated that health-conscious men who decide to take vitamin C
supplements might already be "worried about the state of their arteries." This
type of bias in the study design might explain away any apparent connection
between vitamin C intake and atherosclerosis.
The bottom line, according to Vita, is that patients should not worry about
dietary vitamin C intake. "I certainly would not change my recommendations to
people, which is that they should eat a diet that's rich in fruit and
vegetables, including foods that are high in vitamin C," he said.
When it comes to vitamin C in supplement form, Vita agrees with Dwyer and
the American Heart Association, concluding that "at the moment, there is not
sufficient evidence to say that vitamin C supplements can be recommended."
