According to Dutch Medical Institute of Heart Disease research, drinking tea protects against the build-up of cholesterol in the arteries, especially in women. Results indicated that people who drank one to two cups of tea a day were 46% less likely to develop severe atherosclerosis, rising to 69% in those who drank four cups of tea a day. The protective benefit of tea was most pronounced among women. The authors acknowledge that at least in the West, people who drink tea generally have a healthier lifestyle and diet, which may account for the findings. In this study, for example, the researchers found that people who drank more tea tended to be lean, had a healthy diet, and smoked less.

However the fairly high levels of antioxidant flavonoids in black tea are thought to protect against arterial plaques, the fatty deposits that clog arteries, by preventing fat from being deposited on artery walls. Green tea appears to speed up calorie burning, including fat calorie burning, according to researchers from the University of Geneva in Switzerland. The study authors report that, compared with placebo, treatment with green tea was associated with a "significant increase" (+4%) in daily energy expenditure. They believe that the caffeine interacts with the flavonoids in tea to alter the body's use of norepinephrine, a chemical transmitter in the nervous system, and increase the rate of calorie burning (American Journal of Clinical Nutrition, November 1999).

In Japan, a study of 1,306 males who received the retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1996 and December 1998, showed serum total cholesterol levels were found to be inversely related to the consumption of green tea while no association was noted with serum triglycerides and high-density lipoprotein cholesterol. Adjusted mean concentrations of total cholesterol were 8 mg/dl lower in men drinking nine cups or more of green tea per day than in those consuming zero to two cups per day.

Another Japanese study found that "the main constituent of green tea, EGCG, is a practical cancer chemopreventive agent available in everyday life The British Medical Journal has published a Japanese study on the benefits of green tea consumption in preventing cardiovascular disease, liver disorders and possibly cancer.

The study, begun in 1996, concerned 1371 men over the age of 40. Tea consumption was classified as less than 3 cups, between 4 and 9 cups, and over 10 cups per day. It was found that consumption of green tea was significantly associated with lower serum concentrations of lipids and lipoproteins. "An increase in consumption substantially decreased serum total cholesterol and triglyceride concentrations, and this strong association remained almost unaltered even after age, cigarette smoking, alcohol consumption and relative body weight were controlled for."