Acute effect of ascorbic acid infusion on carbohydrate tolerance.

Large doses (1 to 2g/3 hr) of ascorbic acid were administered intravenously to normal weight and obese, nondiabetic subjects. Glucose tolerance and fasting plasma glucose levels were unaffected, despite a 3- to 8-fold rise in plasma concentrations of the vitamin. Infusion of ascorbic acid did not alter fasting serum insulin levels in normal subjects, but was associated with lower concentrations of hormone during an intravenous glucose tolerance test. Plasma glucose, serum insulin, growth hormone, and glucagon levels in obese subjects remained unchanged during the ascorbic acid infusion.