In a new study, doctors at the Boston University School of Medicine found that heart patients who drank four cups of black tea a day for a month had greatly improved blood circulation. Healthy people's arteries open 13 per cent more when their blood flow is stimulated. But people with heart disease whose blood flow is stimulated only get a 6 per cent increase in their artery opening, says study author Dr. Joseph A. Vita. But after drinking the tea, the heart patients' arteries opened by 10 per cent. "You couldn't say the [heart patients' circulation] was normalized, but they were substantially better," Vita says. The effects of the black tea were comparable to blood circulations improvements achieved by cholesterol-lowering drugs, exercise and, according to the results from another of Vita's recent studies, by vitamin C. Black tea contains flavonoids, antioxidants linked with the reduction of low-density lipoproteins (LDL), the so-called bad cholesterol, in the blood. According to Dr. Vita, one probably has to keep drinking the tea to enjoy its benefits. "Flavonoids have a short life," Vita says. "You need to continuously ingest these kinds of foods for effect." The results of the study appear in the most recent Circulation: Journal of the American Heart Association. According to Dr. Vita, the aim of the study was to test the effects of the tea on the inner lining of the blood vessels, which is called the vascular endothelium. This inner lining produces substances that regulate the dilation and contraction of the vessels, ensuring appropriate blood flow, preventing clots and inflammation in the vessel wall. It is this lining that is often impaired in those with heart disease. In the study, Vita and his colleagues chose 50 men and women who had heart disease; their average age was 55. All had undergone surgery to have a heart artery unblocked or had an artery that was at least 70 per cent blocked. All were on heart drugs and were stable at the time of the study. Half of the study participants were asked to drink four, 8-ounce cups of black tea a day for four weeks, while the other 25 people drank the same amount of water. Then the two groups switched, so that over an eight-week period, all 50 were tested for the effects of consuming black tea compared to water. Their blood flow was measured through an ultrasound of an artery in their arm. Both immediate and long-term measurements showed that the patients' dilation was about 10 per cent when they drank tea, and there was no change after water consumption. Vita is continuing his study of the vascular endothelium in hopes that it will provide clues to predicting heart disease risk. The study was partially funded by grants from the National Institutes of Health and the American Heart Association.