TUESDAY, Feb. 3, 2004 (HealthDayNews) -- High-dose vitamin therapy to reduce blood levels of the amino acid homocysteine in people who had a stroke did not reduce their risk of a second stroke or heart problems.
However, the idea that high blood levels of this acid can cause stroke and heart attacks is still very much alive, researchers say.
In a study of 3,680 stroke patients, the incidence of second strokes, heart problems and death over the next two years was the same in those who got high doses of folic acid and vitamins B6 and B12 as those given low doses, says a report in the Feb. 4 issue of the Journal of the American Medical Association.
No effect was seen even though those on the high-dose vitamins did lower their homocysteine levels.
But high homocysteine levels at the start of the trial were related to the chance of a bad outcome, the report says. People with the lowest levels of homocysteine had a 10 percent lower risk of a second stroke, a 26 percent lower risk of heart disease, and a 16 percent lower risk of death than those with elevated levels.
There are a couple of possible explanations for those apparently contradictory findings, says study leader Dr. James F. Toole, a professor of neurology at Wake Forest University School of Medicine.
"My personal theory is that it might be hard to change the effect of high homocysteine levels late in life," Toole says. "The effort should be started in the 20s. By the time you get atherosclerosis, it's too late to change."
Atherosclerosis is the progressive damage to blood vessels that can end with a heart attack, stroke or other cardiovascular crisis. Homocysteine, which contains sulfur, is believed to contribute to that damage, perhaps by attacking the delicate inner lining of arteries.
Another possibility is that there was a subset of patients whose genetic makeup left them more vulnerable to the ill effects of homocysteine, Toole says. The researchers will be testing that hypothesis by doing genetic studies of blood samples given by people in the study, he says.
The American Heart Association, which acknowledges the relationship between elevated homocysteine levels and risk found in several studies, has a cautious attitude toward therapy.
"We don't recommend widespread use of folic acid and vitamin supplements to reduce the risk of heart disease and stroke," says Carole Bullock, a spokeswoman for the association. "We advise a healthy, balanced diet that includes at least five servings of fruits and vegetables a day."
There can be dangers in self-therapy for homocysteine reduction, Toole says.
"Taking folic acid raw can have an adverse effect on certain people," he says. "There can be some neurological effect. It is dangerous to take a lot of folic acid over a continuing period of time."
People can reduce their risk of heart attack and stroke by eating the right foods and paying attention to other major risk factors, such as obesity and smoking, Toole says, but the uncomfortable fact is that "most Americans don't seem to be doing that."
Taking folic acid and vitamin supplements can be part of a risk-reduction strategy, Toole says, but it's best to talk to a doctor about it.
"First find out of you have elevated levels of homocysteine," he says.
To learn the current status of homocysteine as a cardiac risk, consult the American Heart Association, while you can learn more about brain attacks from the National Institute of Neurological Disorders and Stroke.