Vitamin C (ascorbic acid) is a water-soluble antioxidant with various biological functions. It is essential for the synthesis of collagen and glycosaminoglycans, which are the building materials of all connective tissues, such as skin, blood vessels, tendons, joint cartilage, and bone. Vitamin C supports the body’s defense system by enhancing white blood cell function and activity, and promoting interferon levels, antibody responses, and secretion of thymic hormones. The antioxidative action of vitamin C has been shown to support respiratory, eye, and capillary health. In addition, vitamin C is required for biosynthesis of carnitine, serotonin, and certain neurotransmitters, including norepinephrine.