Stevia leaves get their sweet taste – about 10 to 15 times sweeter than sugar – from natural compounds called steviol glycosides. ... In the sense that steviadoesn't add calories, affect blood sugar or insulin levels, or contribute to dental cavities, I suppose it is a better choice than sugar.
http://www.jrhealthblog.com/what-is-the-most-dangerous-type-of-sugar/