Many people load up on vitamin C and
other nutrients on the assumption that these supplements are good for
their health, even though there is little scientific evidence this is
true. In theory, vitamin C and some other nutrients might protect the
circulatory system and other organs by suppressing the damaging effects
of oxygen.
``When you extract one component of
food and give it at very high levels, you just don't know what you are
doing to the system, and it may be adverse,'' said Dr. James H. Dwyer,
an epidemiologist who directed the study. He presented the findings
Thursday at a meeting in San Diego of the American Heart Association.
Dwyer and colleagues from the University
of Southern California studied 573 outwardly healthy middle-aged men
and women who work for an electric utility in Los Angeles. About 30
percent of them regularly took various vitamins.
The study found no clear-cut sign that
getting lots of vitamin C from food or a daily multivitamin does any
harm. But those taking vitamin C pills had accelerated thickening of
the walls of the big arteries in their necks. In fact, the more they
took, the faster the buildup.
People taking 500 milligrams of vitamin
C daily for at least a year had a 2{ times greater rate of thickening
than did those who avoided supplements. Among smokers, the rate was
five times greater.
``If a person's physician has prescribed
vitamin C, it is appropriate to be taking it,'' Dwyer said. ``But if
you are a healthy person and taking them in hopes of preventing cardiovascular
disease, the heart association does not recommend it. This study would
suggest that recommendation is prudent.''
Dr. Shiriki Kumanyika of the University
of Pennsylvania said the research shows the uncertainties of picking
out a single vitamin among the plethora of nutrients in a healthy diet.
``It's a challenge to sort out what
it is in what people eat that makes them live longer,'' she said. ``We
have to be careful about recommending foods or nutrients, because if
we are wrong, we can do harm.''
In general, experts recommend that people
get their vitamins and other nutrients from fruits, vegetables, whole
grains and nuts.
Clogged arteries what doctors call atherosclerosis
are the major underlying cause of heart attacks and strokes.
In the latest study, doctors looked
for early signs of this process by twice performing ultrasound scans
on the volunteers' carotid arteries, once at the study's start and again
18 months later.
