Impact of vitamin c on exercise-induced oxidative stress and tissue injury

Abstract

The 6-carbon lactone known as ascorbic acid (vitamin C) is a principle water soluble micronutrient within biological systems, where it serves as an electron donor for a variety of physiological processes. Vitamin C is perhaps best known for its role as the primary small molecule antioxidant within aqueous environments. Here it assists other enzymatic and nonenzymatic components of the antioxidant defense system in providing protection against free radical-mediated attack, in an effort to minimize oxidative stress. Simply stated, oxidative stress is a condition in which the production of free radicals exceeds antioxidant defenses, potentially leading to oxidative damage to small and large molecules. Oxidative stress is associated with human disease, as well as the aging process. Although multiple stimuli exist, the performance of acute exercise is one such condition in which the production of free radicals is exacerbated. This exercise-induced oxidative stress has commonly been viewed as a detriment to physical performance, as it is believed to interfere with force production capabilities during exercise, as well as exaccerbate muscle damage and delay recovery in the days following exercise. For this reason, coupled with the aforementioned association of oxidative stress with disease, numerous investigators have attempted to elucidate methods aimed at attenuating such a stress. One such method that has received considerable attention during the past several years is the use of supplemental vitamin C (either alone or in combination with other antioxidant nutrients). Although some investigators have reported a reduction in oxidative stress following vitamin C intake, results are mixed, and controversy exists as to whether such attenuation is really desirable. That is, the consumption of additional vitamin C or other exogenous antioxidants, within otherwise healthy populations, may actually blunt the adaptive improvement in antioxidant defenses commonly observed with regular exercise training. This phenomenon is based on the principle of hormesis and suggests that exercise-induce free radical production may serve as the necessary ?signal? for the induction/regulation of a wide variety of favorable adaptations. At the present time, it would appear that vitamin C supplementation likely possesses no additional benefits related to improved exercise performance in otherwise healthy individuals engaged in regular exercise training who consume a quality diet containing adequate amount of fruits, vegetables, whole grains, and antioxidant-rich oils (fish, flax, olive). However, conditions whereby an individual is continuously exposed to a currently undefined critical level of excessive exercise (i.e., overtraining) may warrant supplementation with vitamin C. Clearly, more research is needed in order to further elucidate the point at which the detrimental effects of exercise begin to outweigh the positive benefits, and at which time intake of supplemental vitamin C may be recommended. © 2011 by Nova Science Publishers, Inc. All rights reserved.

Publication Title

Health Issues, Injuries and Diseases

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