Exercise practitioners often take vitamin C supplements because intense muscular
contractile activity can result in oxidative stress, as indicated by altered muscle and
blood glutathione concentrations and increases in protein, DNA, and lipid
peroxidation. There is, however, considerable debate regarding the beneficial health
effects of vitamin C supplementation. The present study was designed to study the
effect of vitamin C on training efficiency in rats. Thirty male Albino rats were
exercised under protocol for 6 weeks. Ten of the rats were treated with a daily dose of
500 mg/kg body weight of vitamin C (0.24 mg/cm2 body surface area). The
administration of vitamin C hampered endurance capacity. The adverse effects of
vitamin C may result from its capacity toreduce the exercise-induced expression of
key transcription factors involved in mitochondrial biogenesis. These factors are
nuclear respiratory factor 1and mitochondrial transcription factor A. Vitamin C also
prevented the exercise-induced expression ofthe antioxidant enzymes superoxide
dismutase and glutathione peroxidase. The study showed that Vitamin C
supplementation decreases training efficiency because it prevents some cellular
adaptations to exercise.