People with diabetes and hypovitaminosis C fail to conserve urinary vitamin C

Abstract

Background: Hypovitaminosis C has negative health consequences. People with diabetes and hypovitaminosis C may fail to conserve vitamin C in the urine, thereby displaying evidence of inappropriate renal leak of vitamin C. This study describes the relationship between plasma and urinary vitamin C in diabetes, with a focus on the clinical characteristics of participants with renal leak.

Methods: Retrospective analysis of paired, non-fasting plasma and urine vitamin C, and also clinical characteristics, from participants with either type 1 or type 2 diabetes, recruited from a secondary care diabetes clinic. Plasma vitamin C thresholds for renal leak have been defined previously as 38.1 µmol/L for men and 43.2 µmol/L for women.

Results: Statistically significant differences in clinical characteristics were seen between those with; i) renal leak (N = 77) and; ii) hypovitaminosis C but no renal leak (N = 13) and; iii) normal plasma vitamin C levels (n = 34). Compared to participants with adequate plasma vitamin C levels, participants with renal leak tended to have type 2 (rather than type 1) diabetes, a lower eGFR and a higher HbA1c.

Conclusion: In the diabetes population studied, renal leak of vitamin C was common. In some participants, it may have contributed to hypovitaminosis C.

Keywords: BMI, Body mass index, eGFR, estimated glomerular filtration rate; Diabetes; Diabetic nephropathy; HbA1c, glycated haemoglobin, HPLC, high-performance liquid chromatography; MET, Minimal elimination threshold, SGLT2, sodium glucose cotransporter 2; Nutritional and metabolic diseases; Physiopathology; T1 diabetes, Type 1 diabetes, T2 diabetes, Type 2 diabetes; Urine; Vitamin C deficiency.

Fig. 1

Comparison of plasma and urinary vitamin C. Figure 1A shows data for all participants. Figure 1B excludes participants with higher (‘saturating’) concentrations of plasma vitamin C.