UltraCruz canine antioxidant formula is a potent selenium, vitamin C and vitamin E formulation that supports healthy tissues and organs. Selenium and vitamin E, both key antioxidants, work well together to regulate free radicals produced during Exercise. While selenium is active within the cell, vitamin E (d-alpha-tocopherol Acetate), acts within the cell membrane. Selenium, a white blood cell stimulant, helps to maintain a healthy immune system while providing the dog with necessary support. Vitamin E, a fat-soluble vitamin, has been implicated as a cofactor in glucose production and may contribute as a immune system stimulant. Vitamin C (ascorbic acid) functions primarily as an antioxidant.