For most, when you hear the word Stevia, you think of the white powder used as a sugar substitute, which is found in packages or in specific low-calorie products. Stevia is actually a plant that is native to South American. It is referred to as kaa he-he (sweet herb), where it has been used for more than 1,500 years by the Guaran people as a medicinal or sweet treat.
The Stevia plant was first documented in 1887 by Dr. Moises Santiago Bertoni (director of the College of Agriculture in Asuncion, Paraguay) in a botanical journal. It was later named officially after the chemist Rebaudi who identified the plant's compounds.
Stevia is derived from the Stevia rebaudiana plant, which is in the sunflower family. Its active ingredient is steviol glycosides, which is 30-150 times sweeter than sugar. The body does not metabolize glycosides, so it contains no calories.
In 1994 the FDA approved Stevia under the classification of being Generally Recognized as Safe (GRAS). This approval covered products and additives made from the extraction of the Stevia plant. One of the benefits for stevia product manufacturers is that it is heat and pH stable and does not ferment. Surprisingly, the pure leaf was not included in this classification.
In and around 2008, many products can be found in the market place included Truvia and Previa. Some see these highly processed products made for these extracts can be bitter and have a chemical taste, but you will not experience this if you use the pure herb.
Below is some more information from a Ayurvedic and Holistic point of view:
Rasa (taste): Sweet and Pungent
Virya (Energy): Cooling
Vipaka (After Effect: Pungent
Gunas: Light, Cold and Sharp
Dosha Effects: Increases Vata in excess, Reduces Pitta and Kapha