Interactions between vitamins C and E in human subjects

Despite convincing in vitro evidence, a vitamin C-E interaction has not been confirmed in vivo. This study was designed to examine the effects of supplementation with either vitamin C or E on their respective plasma concentrations, other antioxidants, lipids and some haemostatic variables. Fasting blood was collected before and after intervention from thirty healthy adults in a double-blinded crossover study. Baselines for measured variables were established after 2 weeks of placebo supplementation, followed by daily supplementation with 73 . 5 mg RRR-alpha-tocopherol acetate or 500 mg ascorbic acid, and placebo, for 6 weeks. A 2 month washout preceded supplement crossover. Mean values showed that plasma lipid standardised alpha-tocopherol increased with ascorbic acid supplementation: from 4 . 09 (SEM 0 . 51) to 4 . 53 (SEM 0 . 66) mu mol/ mmol total cholesterol plus triacylglycerol (P < 0 . 05), and plasma ascorbic acid increased from 62 . 8 (SEM 14 . 9) to 101 . 3 (SEM 22 . 2) mu mol/l (P < 0 . 005). Supplementation with (RRR)-alpha-tocopherol acetate increased plasma alpha-tocopherol from 26 . 8 (SEM 3 . 9) to 32 . 2 (SEM 3 . 8) mu mol/l (P < 0 . 05), and lipid-standardised alpha-tocopherol from 4 . 12 (SEM 0 . 48) to 5 . 38 (SEM 0 . 52) mu mol/ mmol (P < 0 . 001). Mean plasma ascorbic acid also increased with vitamin E supplementation, from 64 . 4 (SEM 13 . 3) to 76 . 4 (SEM 18 . 4) mu mol/l (P < 0 . 05). Plasma ferric reducing (antioxidant) power and glutathione peroxidase (U/g haemoglobin) increased in both groups, while urate, total cholesterol and triacylglycerol levels decreased (P < 0 . 05 throughout). Results are supportive of an in vivo interaction between vitamins C and E.