Ascorbic acid supplementation reduces oxidative stress and platelet biochemical function in type 2 diabetic patients. Relevance of ascorbic acid dosage and formulation

Background & aims: We investigated the effects of twice daily oral supplementation with different ascorbic acid (AA) dosages and formulations on oxidative stress status and platelet biochemical function in type 2 diabetic patients (T2DP). Methods: Ten T2DP were supplemented with 250 mg/day liquid AA (liq-AA), 10 T2DP with 1,000 mg/day liq-AA and 10 T2DP with placebo for 4 weeks; after suspension of liq-AA supplementation, the 250 mg/day liq-AA and placebo groups were switched to, respectively, supplementation with placebo and 1,000 mg/day chewable AA for further 4 weeks. Plasma AA (P-AA), LDL and erythrocyte lipoperoxides, erythrocyte glutathione peroxidase (E-GSH-Px1) activity and platelet lipoperoxides generated during thrombin-stimulated aggregation were assessed before and after the supplementation periods. Results: Supplementation with 1,000 mg/day liq-AA was significantly more effective than supplementation with 1,000 mg/day chewable AA in increasing P-AA concentration, i.e. by about 93% compared to about 62%, as well as in reducing LDL, erythrocyte and platelet lipoperoxide levels and in augmenting E-GSH-Px1 activity; supplementation with 250 mg/day liq-AA increased only by about 28% plasma AA concentration and was ineffective. Conclusions: Supplementation with 1,000 mg/day liq-AA is most effective in reducing oxidative stress status and platelet biochemical function in T2DP. © 2012 Published by Elsevier Ltd