and three vitamins — folic acid, B-6 and B—12 — may lower homocysteine levels. But the American Heart Association says it is too soon to start telling people to take vitamin supplements to reduce this particular risk. Dr. Ronald Krauss of the Lawrence Berkeley National Laboratory in Berkeley, California and colleagues on the AHA‘s nutrition committee studied results from several trials that looked at the links between homocysteine and heart disease. He said only six out of 11 trials showed a clear association between levels of homocysteine and heart disease. "Until there is proof, rather than emphasising supplements, we should recommend an increased intake of vegetables, fruits, legumes and fortified grains," Krauss told a news conference. Such foods are high in B-vitamins and especially in folic acid, which can also reduce the risk of birth defects when pregnant women get enough. The AHA already recommends eating at least five servings a day of these foods because they also reduce the risk of high blood pressure and of heart disease overall. Krauss noted that some studies do indicate that homocysteine is an independent risk factor. That means that even if a person has normal blood pressure, cholesterol and is not overweight, high homocysteine levels may still point to an increased risk of heart disease. Homocysteine is a product of the metabolism of protein, but levels do not seem to be linked to overall protein in the diet. B vitamins affect it because they help break down homocysteine, Krauss said. Scientists are still not sure if it is the homocysteine that causes some negative effect on the body, or if it is just a marker — a signal that something else is wrong. Dr. Paul Ridker of Brigham and Women‘s Hospital in Boston measured homocysteine in 40,000 healthy women and then waited to see who developed heart disease. "Women who went on to have first-ever cardiovascular events did have higher baseline levels of homocysteine than women who didn‘t," he said. Women whose levels were in the 90th percentile — 90 percent of women had lower levels than they did — had twice the risk of heart disease than women with the lowest levels. And Dr. Winifried Willinek of Medical University Policlinic in Bonn, Germany measured the carotid arteries of people. Thicker carotid arteries — these are arteries in the neck — are linked with heart disease risk. "The higher the levels of homocysteine, the thicker the carotid artery," he said. People who were overweight, who had high blood pressure or high cholesterol also had thicker carotid arteries but high homocysteine was an independent factor.