Multivitamin supplements do not help patients
with heart disease and can make things worse, according to a study presented
here at the Canadian Cardiovascular Congress 2000, co-hosted by the Heart and
Stroke Foundation of Canada and the Canadian Cardiovascular Society.
The antioxidant properties of multivitamin supplements have been widely
touted in the popular media, but the only reliable clinical evidence so far
assembled shows multivitamins to be useless and possibly harmful, says Dr.
Jean Claude Tardif of the Montreal Heart Institute.
Antioxidants are nutrients that help protect cells from a normal - but
damaging - physiological process known as "oxidative stress". Such nutrients
are a part of the natural makeup of many types of food, particularly fruits
and vegetables. They also have been added to some foods and are available in
the form of dietary supplements.
Dr. Tardif has been working with patients who have been treated for the
removal of plaque from their arteries. Plaque deposits cause blood vessels to
become narrowed and can break off and block the artery altogether, causing a
The standard treatment is angioplasty - insertion of a catheter with an
inflatable balloon tip into the artery. The balloon is inflated, the plaque is
compressed and cracked, and the artery is widened. After treatment, the artery
does not re-block in 70% of patients. When arteries become reclogged and the
vessels lapse back into their pre-treatment state the process is called
"The idea behind this study was to try to prevent restenosis with
antioxidants. The hypothesis being that restenosis is a phenomenon driven by
oxidative stress, and, therefore, if you give antioxidants to patients you are
going to prevent restenosis," says Dr. Tardif. "We gave the patients in this
study very high doses of multivitamins because we did not want to be
criticised that we did not give enough to control oxidative stress."
The randomized, double-blinded, placebo-controlled study which took place
over six months involved 317 angioplasty patients divided into four groups. In
one, the patients received probucol - a very potent, synthetic antioxidant -
500 mg twice a day. The next group received high dose multivitamins twice
daily - vitamin E 700 units, vitamin C 500 units and beta carotene 30,000
units. The third group was given a combination of probucol and multivitamins.
The final group got a placebo.
At the beginning and end of the study, intravascular ultrasound was used
to measure the width of the plaque-affected arteries of patients.
"The result showed that the synthetic antioxidant, probucol, is extremely
effective at preventing restenosis and the multivitamins are completely
useless," says Dr. Tardif.
One mechanism by which restenosis occurs in arteries that have been
treated with balloon angioplasty is chronic vascular recoil, also called
negative vascular remodelling. Dr. Tardif's study has shown that probucol, the
synthetic antioxidant, is extremely effective at improving adaptive vascular
enlargement or positive vascular remodeling.
However, the same study shows that multivitamins not only fail to improve
remodeling but also tend to make arteries more fibrotic (promotes unhealthy
growths on the inside wall of the artery). Therefore multivitamins accelerate
collagen accumulation and undo the beneficial effect of angioplasty.
"High dosage multivitamins produce no vascular remodelling and adversely
affect plaque composition after angioplasty," concludes Dr. Tardif.