Stevia is a sweetener used as a no-calorie sugar substitute. Stevia sweeteners are up to 350 times sweeter than sugar, so only small amounts are needed to sweeten foods and drinks. Stevia sweeteners are derived from the leaves of the stevia plant, which is native to South America. Sweeteners made from stevia do not affect blood glucose or insulin levels negatively, and its natural plant-based origins make it a popular sugar substitute.