Handbook of Vitamin C Research

Impact of Vitamin C on Exercise-Induced Oxidative Stress 21of the relevant studies that have investigated the efficacy of vitamin C will be discussedbelow in relation to both aerobic and anaerobic exercise, in both humans and animals.Aerobic Exercise: Human StudiesThe majority of investigations related to the effects of vitamin C on reducing exerciseinducedoxidative stress and tissue injury have utilized aerobic exercise as the stimulus. Dueto the large number of studies and variability in terms of types of protocols used, results areseparated via the mode of aerobic exercise employed, as both concentric (both moderate andlong duration) and eccentric protocols have been utilized. For the purposes of this review,moderate duration is considered as any aerobic protocol performed for a duration of less thantwo hours, whereas long duration refers to exercise involving greater than two hours induration and/or performed in a field setting (e.g., duathlon, marathon, ultramarathon, etc.).Studies are separated based on whether vitamin C treatment was administered independentlyor in conjunction with other antioxidants.Vitamin C AloneConcentric, Short Duration ProtocolsWith respect to the effects of acute ingestion of vitamin C prior to an acute aerobicexercise stimulus on markers of oxidative stress and tissue injury, Ashton and colleagues[107] reported no increase in the direct production of RONS (PBN adducts measured viaelectron spin resonance), or in two indirect indices of lipid peroxidation (MDA and LOOH)following acute administration of 1000mg of vitamin C administered two hours prior to theperformance of a graded exercise test (GXT), despite an increase in all markers followingplacebo intake. These results were mimicked in two similar studies conducted by Davison etal. [111,123] over a decade later, in both healthy [111,123] and diabetic [123] subjects. Theyreporting identical effects of acute vitamin C ingestion in preventing the increase in PBNadducts and MDA following a GXT. In support of the above, several other studies havereported an attenuating effect of acute vitamin C ingestion on various markers of oxidativestress (Nitrite [124], TBARS [125], CD [126], MDA [127], TAC [127]) following acutemaximal (GXT) or submaximal aerobic exercise (30 minute treadmill run at 75% VO 2max[125,127] or a 10.5 km run [126]). Regarding the effects of acute vitamin C intake inattenuating muscle injury in response to acute concentric aerobic exercise, one study reportedan attenuation of both CK and DOMS following intake of 2000mg of vitamin C, taken twohours pre exercise [127].These effects of acute ingestion of vitamin C in attenuating exercise-induced oxidativestress and tissue injury appear evident despite supplementation (1000mg vitamin C 2h preexercise) reportedly resulting in exacerbated production of the ascorbate free radical (AFR)[124]. Changes in the levels of AFR are indicative of both an oxidative stress andantioxidant response in the plasma [128]. In this respect, the attenuation of various markersof oxidative stress following vitamin C intake likely results from the scavenging ability of the