March 12, 2006
Lowering homocysteine doesn’t protect heart: studies
By Gene Emery
BOSTON (Reuters) - Levels of the amino acid homocysteine
may be high in people destined for a heart attack or stroke,
but lowering them with B vitamins and folic acid does not
reduce the risk, two studies show.
"Clearly, folic acid, vitamin B12, and vitamin B6 are not
the therapeutic solution expected," said Joseph Loscalzo of
Brigham and Women's Hospital in Boston, in an editorial in The
New England Journal of Medicine, where the results will appear.
They were reported on Sunday at the annual meeting of the
American College of Cardiology in Atlanta.
In the first study, Eva Lonn of McMaster University in
Ontario and her colleagues gave 5,522 volunteers from 13
countries either a placebo or supplements of vitamin B6, B12
and folic acid.
In the group that received the supplements, homocysteine
levels declined. But the likelihood of stroke, heart
attack, or death from any heart-related cause did not.
The rate of heart problems or stroke was 18.8 percent for
volunteers getting the supplements and 19.8 percent for the
Even when they thought they might be seeing some benefit
from folic acid or B vitamins, that was offset by an increased
risk of another health problem, the Lonn team found.
The risk of stroke seem to fall by 25 percent for
supplement recipients, but 24 percent more ended up being
hospitalized for unstable angina, which can quickly lead to a
heart attack. Both findings, the researchers cautioned, may
have been due to chance.
While the Lonn study looked at people over 54 with diabetes
or who were at risk of heart disease, the second smaller trial
examined 3,749 Norwegians who started taking supplements or a
placebo within seven days after surviving a heart attack.
That team, led by Kaare Bonaa of the University of Tromso,
also found no clear benefit after about three years of
Volunteers who took folic acid and the two B vitamins
actually seemed to face a higher risk of a stroke, heart attack
or death from any heart-related cause.
However, that 22-percent increase in the risk was barely
statistically significant, so it could have been due to chance.
Patients who lowered their homocysteine levels by only taking
vitamin B6, or a combination of B12 and folic acid, saw their
risk increase by 8 to 14 percent.
"Such therapy may even be harmful" to people who have just
survived a heart attack or had a stent implanted to prevent
another heart attack "and should therefore not be recommended,"
said the Bonaa team.
Population studies have, in the past, linked homocysteine
to an increased risk of heart disease.
Because homocysteine levels are related to kidney problems,
smoking, high blood pressure and other factors that increase
the risk of heart disease, "homocysteine could be a marker, but
not a cause, of vascular disease," the Lonn team said.