Effect of vitamin C supplementation on concentrations of vitamins C and E in fasting plasma.

Vitamin C may 'spare' vitamin E, but this has not to date been confirmed as occurring in vivo. The aim of this study was to test the effect of dietary supplementation with vitamin C on total and lipid standardised vitamin E concentrations in fasting plasma, the hypothesis being that increased vitamin C intake leads to improved vitamin E levels. In this single-blinded study, 12 apparently healthy adults (seven men, five women) took 1 g/day vitamin C for 28 days, with a 28-day placebo-controlled run-in cycle and a 28-day placebo-controlled washout cycle. Concentrations of ascorbic acid, total vitamin E (as total tocopherols) and lipid standardised vitamin E (Vit ELS, expressed as mol vitamin E/mmol total cholesterol plus triglycerides) were measured in fasting plasma after each cycle. Results showed that vitamin C supplementation led to significant increases in ascorbic acid, total vitamin E and Vit ELS. These findings indicate that, by a combination of a vitamin E 'sparing' effect perhaps via improved redox recycling of vitamin E in vivo and a lipid lowering effect, increased intake of vitamin C could increase plasma vitamin E levels, and possibly vitamin E status. Further study of possible in vivo interrelationships between vitamins C and E, and the role of vitamin C in lipid metabolism, is needed.