Vitamin C plays a major role in the formation of collagen, a component of connective tissue that provides structure for skin, cartilage, tendons and ligaments. This essential nutrient also participates in amino acid metabolism and hormone synthesis, and in the utilization of other nutrients such as iron. It is also a key factor in the body's immune system. Vitamin C is unusual in that it is synthesized by most mammals, but not by humans and other primates, making supplementation desirable. Vitamin C is a potent reducing agent and antioxidant and may help regenerate oxidized vitamin E.