Free Radicals, Antioxidants and Exercise
James Meschino DC, MS, ROHP
Strenuous exercise has been shown to increase the production of reactive oxygen species (free radicals) due to increased oxygen utilization. Free radicals can damage muscle tissue, leading to inflammation and soreness, as well as increased oxidative stress to body in general. Exercising in the presence of air pollution (nitrous oxide etc) has also been shown to increase oxidative stress to lung tissues and the general circulation. Studies reveal that supplementation with various antioxidants lowers indirect markers of oxidative stress (e.g., blood levels of dimethylmalonaldehyde and breath pentane in expired air). Vitamin E (400 – 1,200 IU per day) has been shown to provide this benefit, and to protect lung tissue as well. Vitamin C and Beta-carotene supplementation at 400 – 3,000 mg and 25,000 IU, respectively, have also been shown to minimize oxidative stress induced by exercise.
Several studies (double-blind) indicate that antioxidant supplementation in the above noted ranges may also reduce pain and speed up muscle recovery after intense exercise by reducing free radical damage to muscles.
Vitamin C supplementation (600 mg per day) was also shown to reduce the incidence of upper respiratory tract infections in marathon runners within 14 days of completing a 90 km race (33% incidence) compared to the placebo group (68% incidence). Marathon runners have also been shown to have lower blood levels of Vitamin C (by 20%) after completing a 21 km run, and demonstrate increased excretion of Vitamin C in their sweat and urine (Peters et al AJCN, 1993). Another study, using a combination of Vitamin E, Vitamin C and Beta-carotene supplementation, revealed that exercising individuals taking the daily antioxidant supplement cocktail for 90 days had significantly higher levels of blood glutathione and increased superoxide dismutase and catalase enzyme activity in circulating neutrophils, than did the placebo group.
Recent studies also confirm that supplementation with vitamin E, vitamin C, and beta-carotene, reduce free radical damage to skin cells induced by exposure to ultra-violet light. During their development in the deeper layers of the epidermis, epidermal cells absorb antioxidants from the blood stream, which provides them with added antioxidant protection against sun-light induced photo-aging and against the free radical damage that causes mutations to their genetic material, which are linked to skin cancers, including melanoma, squamous cell, and basal cell carcinoma. It should also be note that ultra-violet light depletes antioxidants within the skin, which increases demand for higher intake levels of nutritional antioxidants to replenish these stores. Skin surface lipids, a mixture of lipids excreted from epidermal cells in combination with secretions from sebaceous glands, also contain antioxidants that are derived from dietary and supplemental sources.
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( additional reading – Kenneth Cooper, The Antioxidant Revolution).