COULD CO-ADMINISTRATION OF VITAMINS E AND C INCREASE TOTAL ANTIOXIDANT CAPACITY? A SYSTEMATIC REVIEW AND META-ANALYSIS

The aim of this meta-analysis was to assess effects of supplementation with vitamin E, vitamin C or a combination of the two vitamins on total antioxidant capacity (TAC) in clinical trial studies. A systematic search was carried out for clinical trials in PubMed, Scopus and Cochrane Library databases published up to July 2017. Of 4176 relevant studies searched, only 17 studies with 9, 8 and 10 arms selected respectively for the meta-analysis assessing the effects of vitamin E, vitamin C and a combination of the two vitamins on TAC. Pooled effects analysis showed that co-administration of vitamins E and C could significantly increase TAC by 0.09 mmol/l (95% CI= 0.03, 0.16; P < 0.001). In sub-group analysis based on the supplementation dose and trial duration, no differences were seen in TAC between the groups. Meta regression analysis showed that the baseline TAC included a significant association with the effects of vitamin E (P = 0.001), vitamin C (P < 0.001) and a combination of the two vitamins (P = 0.004) on the final TAC. Results of the current meta-analysis showed that co-administration of vitamins E and C could significantly increase the TAC.KEY WORDS: Meta-analysis, TAC, Total antioxidant capacity, Vitamin C, Vitamin E