The highly purified stevia extracts found in supermarkets are recognized as generally safe by the U.S. Food and Drug Administration. Crude and whole-leaf extracts are not approved by the FDA.
Stevia has been used as a sweetener for centuries in its native South America. The stevioside in stevia makes it 100 to 300 times sweeter than sugar, with no calories. Stevia extracts were first developed in Japan in the early 1970s after extensive research found them to be extremely safe. Studies also show stevia to be beneficial in treating high blood pressure and obesity. Because it has little effect on blood glucose, it is suitable for use by diabetics and those on low-carb diets.