Tagatose is a low carbohydrate functional sweetener, very similar to fructose in structure. It is naturally occurring and can be found in some dairy products. Tagatose has a physical bulk similar to sucrose or table sugar and is almost as sweet. However, it is metabolized differently, has a minimal effect on blood glucose and insulin levels and furthermore provides a prebiotic effect. Tagatose is especially suitable as a flavor enhancer or as a low carbohydrate sweetener.
I wonder why it's not more popular.