Supplementation with vitamin C and N-acetyl-cysteine increases oxidative stress in humans after an acute muscle injury induced by eccentric exercise

There has been no investigation to determine if the widely used over-the-co unter, water-soluble antioxidants vitamin C and N-acetyl-cysteine (NAC) cou ld act as pro-oxidants in humans during inflammatory conditions. We induced an acute-phase inflammatory response by an eccentric arm muscle injury. Th e inflammation was characterized by edema, swelling, pain, and increases in plasma inflammatory indicators, myeloperoxidase and interleukin-6. Immedia tely following the injury, subjects consumed a placebo or vitamin C (12.5 m g/kg body weight) and NAC (10 mg/kg body weight) for 7 d. The resulting mus cle injury caused increased levels of serum bleomycin-detectable iron and t he amount of iron was higher in the vitamin C and NAC group. The concentrat ions of lactate dehydrogenase (LDH), creatine kinase. (CK), and myoglobin w ere significantly elevated 2, 3, and 4 d postinjury and returned to baselin e levels by day 7. In addition, LDH and CK activities were elevated to a gr eater extent in the vitamin C and NAC group. Levels of markers for oxidativ e stress (lipid hydroperoxides and 8-iso prostaglandin F-2 alpha; 8-Iso-PGF (2 alpha)) and antioxidant enzyme activities were also elevated post-injury . The subjects receiving vitamin C and NAC had higher levels of lipid hydro peroxides arid 8-Iso-PGF(2 alpha) 2 d after the exercise. This acute human inflammatory model strongly suggests that vitamin C and NAC supplementation immediately post-injury, transiently increases tissue damage and oxidative stress. (C) 2001 Elsevier Science Inc.