Blood vitamin C concentrations in patients with diabetes mellitus.

Plasma and buffy layer vitamin C concentrations have been measured in insulin dependent and non-insulin dependent diabetic patients and the results compared with age and gender matched non-diabetic controls. No differences were found between the controls and the diabetics nor between the different types of diabetes, although patients who had had clinical diabetes for longer had higher plasma vitamin C values than patients in whom the disease was not long standing. There were no significant changes in the distribution of vitamin C between plasma and white cells in the diabetic nor in patients with marked hyperglycaemia. We conclude that the vitamin C intakes of the majority of diabetic patients we studied, who are probably typical of diabetics receiving hospital treatment in the United Kingdom, are adequate and are sufficient to maintain satisfactory plasma and buffy layer vitamin C concentrations. These findings are discussed in the light of reports which have shown lower levels of vitamin C in the blood of diabetic patients and competition between vitamin C and glucose for transport across the cell membrane.