BOSTON, Mar 13 (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 yesterday 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 per cent for volunteers getting the supplements and 19.8 per cent for the placebo recipients.
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 per cent for supplement recipients, but 24 per cent more ended up being hospitalised 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 treatment.
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-per cent 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 per cent.
''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.
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