Glycerine is a clear, viscous liquid, which dissolves completely in water. It occurs widely in nature, and was traditionally obtained from animal fat or tallow as a by-product of soap making. Glycerine is not metabolised as sugar in the body and doesn't cause a rise in blood sugar. For that reason, it's sometimes used as a sweetener in foods marketed to diabetics and low-carb dieters. In food and beverages, glycerine serves as a humectant, solvent, and sweetener, and may help preserve foods.