Five-week-old moderately diabetic and severely diabetic mice were fed the compound, an antioxidant called epigallocatechin gallate or EGCG, or given Avandia. The rodents' blood sugar and insulin levels were studied after five and 10 weeks of treatment. The moderately diabetic mice fared as well on green tea extract as they did on Avandia, also known as rosiglitazone, the researchers reported. EGCG was not as effective in the severely diabetic group.

"Although EGCG was less potent than rosiglitazone, it exerted changes that were similarly beneficial," researchers led by Ake Sjoeholm of Sweden's Karolinska Institute wrote in an abstract of the study presented Wednesday at the European Association for the Study of Diabetes meeting in Amsterdam.

The animal study suggests that supplements of green tea extract may help prevent and treat the disease in people.

More than 240 million people worldwide suffer from diabetes and the number may rise to 380 million within 20 years, according to the International Diabetes Federation.

At the end of the trial, the researchers examined cells in the mice's pancreases. The green tea extract preserved insulin- producing tissue and limited damage linked to a worsening of diabetes, according to Sjoeholm and his colleagues.

Green tea was suggested as a treatment for diabetes more than 70 years ago. A study of more than 16,000 Japanese men and women, published in the Annals of Internal Medicine last year, found that those who drank more than six cups of green tea or three cups of coffee a day were less likely to develop type-2 diabetes than those who drank less than one cup of either beverage a week.

Other studies have shown possible benefits of green tea in cancer and heart disease prevention. Theanine, an amino acid present in black, green and oolong teas, may improve the ability to concentrate, according to a study presented Tuesday at a conference at the U.S. Department of Agriculture in Washington. The research was sponsored by Unilever Plc, which includes Lipton Tea among its more than 400 brands.