By Suzanne Leigh, Medical Tribune News Service
High
blood levels of an amino acid described by scientists as ``the
new cholesterol'' can increase heart-disease risk, according to
a new study.
Homocysteine
was first identified as a suspect in heart disease 30 years ago
by Dr. Kilmer McCully of the Harvard Medical School in Boston.
Since then, a number of studies have examined the link between
homocysteine and heart disease, but findings have been contradictory.
New
research published on Wednesday in the Journal of the American
Medical Association indicates that postmenopausal women whose
homocysteine levels were elevated faced a ``moderately increased
risk of future cardiovascular disease.''
In
the study, researchers led by Dr. Paul Ridker at Brigham and Women's
Hospital in Boston tracked the medical records of 28,263 women,
average age 59, who had no history of heart disease or cancer.
During
a three-year follow-up, 122 women in this group had a heart attack,
heart surgery or stroke. These women were matched by age and smoking
status with 244 women who did not have heart surgery, heart attack
or stroke during the follow-up period.
When
researchers compared the homocysteine levels of the two groups,
they found that those with the highest levels of the amino acid
in their blood had double the risk of heart disease. Although
this risk was ``modest in absolute size,'' it appeared to be independent
of factors like high blood pressure and diabetes.
Homocysteine
is produced naturally as a byproduct of the body's breakdown of
protein. Some doctors believe it damages blood-vessel walls by
increasing the buildup of plaque, or fatty material, in the arteries.
Women
in the study who took multivitamin supplements had lower homocysteine
levels. Multivitamins contain folic acid, a B vitamin that has
been found to lower homocysteine levels.
But
while it is clear that folic acid decreases homocysteine, it is
less clear what role it plays in reducing heart-disease risk,
according to the authors.
Gauging the effectiveness of multivitamins in preventing heart
disease would require randomized controlled testing involving
a placebo, they concluded.
The
Ridker study follows similar research published last year in The
New England Journal of Medicine. Lead author Dr. M. Rene Malinow
of Providence St. Vincent Medical Center in Portland, Ore., studied
75 adults with heart disease who each consumed a daily breakfast
cereal. Some participants' cereal was fortified with 400 micrograms
of folic acid. At the end of the study the folic acid group achieved
an 11 percent drop in homocysteine, compared with an insignificant
reduction in the placebo group.
But
while the results of both studies are promising, it is probably
too early to recommend routine homocysteine screening, according
to Dr. Robert M. Siegel, medical director of Advanced Cardiac
Specialists in Phoenix.
``My
enthusiasm to pursue and treat elevated homocysteine levels is
higher than it was five years ago, but we don't yet know enough
about how they impact cardiovascular disease,'' he said.
Current
information indicates that high homocysteine levels do not merit
the same high-risk status as conditions like diabetes, smoking,
family history of heart disease and high cholesterol, according
to Siegel.
``Until
we have a large-scale double-blind clinical trial, involving placebo,
it's difficult to make a general recommendation. But high-risk
patients should be evaluated for homocyteine in order to cover
all bases,'' said Siegel.
