Vitamin C is the body's principal water-soluble antioxidant. Vitamin C is synthesized from glucose in the horse's liver and aids in hemoglobin production as well as works synergistically with Vitamin E and other antioxidants. Vitamin C is required for the synthesis of Tryptophan, Lysine and Proline, all of which are critical to normal collagen production, and vitamin C may help reduce normal oxidative stress.