Interactions between vitamins C and E in human subjects

Despite convincing in vitro evidence, a vitamin C-E interaction has not bee n confirmed in vivo. This study was designed to examine the effects of supp lementation with either vitamin C or E on their respective plasma concentra tions, other antioxidants, lipids and some haemostatic variables. Fasting b lood 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 su pplementation with 73 . 5 mg RRR-alpha-tocopherol acetate or 500 mg ascorbi c acid, and placebo, for 6 weeks. A 2 month washout preceded supplement cro ssover. 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 10 1 . 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 alph a-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 suppl ementation, 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 peroxida se (U/g haemoglobin) increased in both groups, while urate, total cholester ol and triacylglycerol levels decreased (P < 0 . 05 throughout). Results ar e supportive of an in vivo interaction between vitamins C and E.