Interactions between vitamins C and E in human subjects

Abstract

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-α-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 α-tocopherol increased with ascorbic acid supplementation: from 4.09 (SEM 0.51) to 4.53 (SEM 0.66) μmol/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) μmol/l (P<0.005). Supplementation with (RRR)-α-tocopherol acetate increased plasma α-tocopherol from 26.8 (SEM 3.9) to 32.2 (SEM 3.8) μmol/l (P<0.05), and lipid-standardised α-tocopherol from 4.12 (SEM 0.48) to 5.38 (SEM 0.52) μmol/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) μmol/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.