Metabolic benefits deriving from chronic vitamin C supplementation in aged non-insulin dependent diabetics

Objective: Our study investigated the metabolic benefits deriving from chronic pharmacological vitamin C administration in aged non-insulin dependent (Type II) diabetic patients. Methods: Forty type II diabetic patients (age: 72 ± 0.5 years) underwent placebo and vitamin C (0.5 g twice daily) administration in double-blind, randomized, cross-over fashion. All patients were treated by oral hypoglycaemic agents which continued throughout the study. After baseline observations, treatment periods lasted 4 months and were separated by a 30-day wash-out period. Results: Patients' antropometric data were unchanged throughout the study. Chronic vitamin C administration vs placebo was associated with a significant decline in fasting plasma free radicals (0.26 ± 0.06 vs 0.49 ± 0.07 p < 0.03) and insulin (90 ± 4 vs 73 ± 6 pmol/L p < 0.04), total- (7.3 ± 0.5 vs 5.8 ± 0.4 mmol/L p < 0.03), LDL-cholesterol (5.6 ± 0.6 vs 4.1 ± 0.3 mmol/L p < 0.05) and triglycerides (2.58 ± 0.07 vs 2.08 ± 0.04 mmol/L p < 0.04) levels. In 20 patients, chronic vitamin C administration improved whole body glucose disposal and nonoxidative glucose metabolism. Percent increase in plasma vitamin C levels correlated with the percent decline in plasma LDL-cholesterol (r = 0.44; p < 0.007) and insulin levels (r = 0.42; p < 0.006). Finally percent increase in plasma vitamin C levels was correlated with the percent decline in plasma free radicals and increase in GSH levels. Conclusions: Chronic vitamin C administration has beneficial effects upon glucose and lipid metabolism in aged non-insulin dependent (type II) diabetic patients.