The genus Stevia consists of 240[6] species of plants native to South America, Central America, and Mexico, with several species found as far north as Arizona, New Mexico, and Texas.[7] Human use of the sweet species S. rebaudiana originated in South America. The leaves of the stevia plant have 30–45 times the sweetness of sucrose (ordinary table sugar).[8] The leaves can be eaten fresh, or put in teas and foods.
In 1899, The Swiss botanist Moisés Santiago Bertoni first described the plant and the sweet taste in detail.[9] But only limited research was conducted on the topic, until in 1931, two French chemists isolated the glycosides that give stevia its sweet taste.[10] These compounds were named stevioside and rebaudioside, and are 250–300 times sweeter than sucrose, heat stable, pH stable, and non-fermentable.[11]
The exact structure of the aglycone and the glycoside were published in 1955.
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,[12] the Japanese have been using stevia in food products, soft drinks (including Coca Cola),[13] and for table use. Japan currently consumes more stevia than any other country, with stevia accounting for 40% of the sweetener market.[14]
Today, stevia is cultivated and used in food elsewhere in east Asia, including in China (since 1984), Korea, Taiwan, Thailand, and Malaysia. It can also be found in Saint Kitts and Nevis, in parts of South America (Brazil, Colombia, Peru, Paraguay, and Uruguay) and in Israel. China is the world's largest exporter of stevioside.[14]
Stevia species are found in the wild in semi-arid habitats ranging from grassland to mountain terrain. Stevia does produce seeds, but only a small percentage of them germinate. Planting cloned stevia is a more effective method of reproduction.
Medicinal use
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.[15]
More recent medical research has shown promise in treating obesity[16], high blood pressure, and hypertension.[17][18]
Stevia has a negligible effect on blood glucose, even enhancing glucose tolerance;[19] therefore, it is attractive as a natural sweetener to diabetics and others on carbohydrate-controlled diets.[20]
Possible treatment of osteoporosis has been suggested by observations that eggshell breakage can be reduced by 75% by adding a small percentage of stevia leaf powder to chicken feed, and that pigs given 2% stevia leaf powder in their feed experienced a doubling of serum calcium.[21]
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