Louo han guo is a fruit that has been recently hyped up and marketed as a natural sweetener. What is it really? It's really just a source of xylitol. Xylitol is a natural sugar alcohol, which is not digested as easily by the body lending fewer calories per gram than regular sugar. The polyol also has a slight cooling effect, which you would recognize while eating sugarless gum like Trident.
Xylitol was first discovered and isolated in Sweden from birch bark. It is also now widely used in Sweden (where it was first isolated) and used in all sorts of candies there.
Regular use of xylitol is associated with significant reduction of cavities and tooth remineralization (1). Why? Because research shows that xylitol doesn't contribute to tooth decay and, unlike other sugar alcohols like erythritol, it may even help fight cavities by a mechanism of confusing cavity-causing bacteria to eat it and basically die.
1. Mäkinen KK. Sugar alcohols, caries incidence, and remineralization of caries lesions: a literature review. Int J Dent. 2010;2010:981072. Epub 2010 Jan 5.