Vitamin C and Vitamin E are crucial antioxidants. Oxidative stress and free radical attack on the immune system caused by exercise is theoretically one of the reasons why moderately and highly intensive exercise can impair immunity. Antioxidants, including VC, VE and various enzymes are common supplements for exercisers. Studies have suggested that taking these antioxidants can reduce the attacks of oxidative free radicals, so as to beef up the immune function.taking these antioxidants can help the body reduce the attacks of oxidative free radicals, so as to beef up the immune function.