Antioxidants
show no clear benefit against cardiovascular
events, death in high-risk women
Vitamins C and E and beta carotene, either
individually or in combination, do not appear to
reduce the risk of cardiovascular events or
death among women at high risk for heart
disease, according to a report in the August
13/27 issue of Archives of Internal Medicine,
one of the JAMA/Archives journals.
Oxidative damage—harm to cells caused by exposure
to oxygen—may contribute to the development of
cardiovascular disease, according to background
information in the article. In addition,
compounds known as free radicals may damage
artery linings, encourage blood clots and alter
the function of blood vessels.
“Antioxidants scavenge free radicals and
limit the damage they can cause,” the authors
write. “Diets high in fruit and vegetable
intake, and thus rich in such antioxidants, have
been associated with reduced rates of coronary
heart disease and stroke. Vitamins C and E and
beta carotene are potential mediators of the
apparent protective effect of a plant-based diet
on cardiovascular disease.”
Nancy R. Cook, Sc.D., of Brigham & Women’s
Hospital and Harvard Medical School, Boston, and
colleagues tested the effects of these compounds
in the Women’s Antioxidant Cardiovascular Study,
which followed 8,171 women 40 years or older
(average age 60.6) beginning in 1995 to 1996.
The women, who either had a history of
cardiovascular disease or three or more risk
factors, were randomly assigned to take 500
milligrams of ascorbic acid (vitamin C) or
placebo every day; 600 international units of
vitamin E or placebo every other day; and 50
milligrams of beta carotene or placebo every
other day. Participants were followed up for the
occurrence of heart events (including stroke,
heart attack and bypass surgery) or death
through 2005.
During the average study period of 9.4 years,
1,450 women had one or more cardiovascular
events, including 274 heart attacks, 298
strokes, 889 coronary revascularization
procedures (bypass surgery or angioplasty) and
395 cardiovascular deaths (out of a total 995
deaths).
“There was no overall effect of ascorbic acid,
vitamin E or beta carotene on the primary
combined end point or on the individual
secondary outcomes of myocardial infarction,
stroke, coronary revascularization or
cardiovascular disease death,” the authors
write. “There were no significant
interactions between agents for the primary
end point, but those randomized to both
active ascorbic acid and vitamin E
experienced fewer strokes.”
No additional adverse effects were observed for
those taking active pills vs. placebo, with the
exception of a small increase in reports of
upset stomach among those taking active beta
carotene.
“Overall, we found no benefit on the primary
combined end point for any of the antioxidant
agents tested, alone or in combination,” the
authors conclude. “We also found no evidence for
harm. While additional research into
combinations of agents, particularly for stroke,
may be of interest, widespread use of these
individual agents for cardiovascular protection
does not appear warranted.”
