The active compounds of stevia are steviol glycosides (mainly stevioside and rebaudioside), which have up to 150 times the sweetness of sugar, are heat-stable, pH-stable, and not fermentable. These steviosides have a negligible effect on blood glucose, which makes stevia attractive to people on carbohydrate-controlled diets. Stevia’s taste has a slower onset and longer duration than that of sugar, and some of its extracts may have a bitter or licorice-like aftertaste at high concentrations.
The legal status of stevia extracts as food additives and supplements varies from country to country. In the United States, stevia was banned in 1991 after early studies found that it might be carcinogenic; after additional studies, the FDA approved some specific glycoside extracts for use as food additives in 2008.