Stevia (, or ) is a sweetener and sugar substitute extracted from the leaves of the plant species Stevia rebaudiana. 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 Japan, for example, stevia has been widely used for decades as a sweetener. In some other countries, health concerns and political controversies have led to various restrictions, or outright prohibition. The United States, for example, banned stevia in the early 1990s and only approved some specific glycoside extracts for use as food additives in 2008. The European Union only approved stevia additives in 2011.