Vitamins C and E: acute interactive effects on biomarkers of antioxidant defence and oxidative stress.

ABSTRACT

Oxidative stress is implicated in the aetiology of many diseases; however, most supplementation trials with antioxidant micronutrients have not shown expected beneficial effects. This randomized, double-blinded, placebo-controlled study evaluated acute effects (at 90, 180min and 24h [fasting] post-ingestion) of single doses of Vitamins C (500mg) and E (400IU), alone and in combination, on biomarkers of plasma antioxidant status, lipid peroxidation and lymphocyte DNA damage in 12 healthy, consenting volunteers. Plasma ascorbic acid increased significantly (P < 0.01) within 2h of ingestion of Vitamin C, and alpha-tocopherol was significantly (P < 0.01) higher at 24h post-ingestion Vitamin E. The pattern of response was not significantly different whether Vitamin C (or Vitamin E) was taken alone or in combination, indicating no augmentation of response to one by co-ingestion of the other vitamin. No significant changes were seen in plasma FRAP in the group overall (although increases (P < 0.05) were seen at 90 and 180min post-ingestion in women after Vitamin C ingestion) or in MDA across treatments, and no evidence of increased DNA damage, or of DNA protection, was seen at any time point after Vitamin C and/or E ingestion. In conclusion, the data from this first controlled study of acute effects of single doses of Vitamin C and/or E show no evidence of either a protective or deleterious effect on DNA damage, resistance of DNA to oxidant challenge, or lipid peroxidation. No evidence of a synergistic or cooperative interaction between Vitamins C and E was seen, but further study is needed to determine possible interactive effects in a staggered supplementation cycle, and study of subjects under increased oxidative stress or with marginal antioxidant status would be useful. It would be of interest also to study the effects of these vitamins ingested with, or in, whole food, to determine if they are directly protective at doses above the minimum required to prevent deficiency, if combinations with other food components are needed for effective protection, or if Vitamins C and E are largely surrogate biomarkers of a 'healthy' diet, but are not the key protective agents.