The leaves of the stevia plant have 30–45 times the sweetness of sucrose (ordinary table sugar).The leaves can be eaten fresh, or put in teas and foods.For centuries, the Guaraní tribes of Paraguay and Brazil used stevia, which they called ka'a he'ê ("sweet herb"), as a sweetener in yerba mate and medicinal teas for treating heartburn and other ailments. More recent medical research has shown promise in treating obesity, high blood pressure, and hypertension. Stevia has a negligible effect on blood glucose, even enhancing glucose tolerance; therefore, it is attractive as a natural sweetener to diabetics and others on carbohydrate-controlled diets. In the early 1970s, Japan began cultivating stevia as an alternative to artificial sweeteners such as cyclamate and saccharin, which were suspected carcinogens. The plant's leaves, the aqueous extract of the leaves, and purified steviosides are used as sweeteners. Since the Japanese firm Morita Kagaku Kogyo Co., Ltd. produced the first commercial stevia sweetener in Japan in 1971, the Japanese have been using stevia in food products, soft drinks (including Coca Cola), and for table use. Japan currently consumes more stevia than any other country, with stevia accounting for 40% of the sweetener market.