D-Galactose (D-Galactopyranose, D-(+)-Galactose) is an aldohexose that occurs naturally in the D-form in lactose, cerebrosides, gangliosides, and mucoproteins and is converted enzymatically into D-glucose for metabolism or polysaccharides for storage. It accelerates senescence in invertebrates and mammals and has been used as a model for aging.