Understanding the additional impact of prediabetes and type 2 diabetes mellitus on vitamin C requirements in people living with obesity.

Obesity and diabetes are known to negatively affect vitamin C status. However, whether the presence of diabetes, in addition to obesity, contributes an additional impact on vitamin C status is currently uncertain. In a cohort of 152 adults living with obesity, we assessed metabolic and nutrient parameters in participants without diabetes (n = 92), and with prediabetes (n = 22) and type 2 diabetes mellitus (T2DM; n = 35). Vitamin C concentrations were measured in plasma and leukocytes using HPLC and vitamin C intakes were assessed using 24-hour dietary recall. Metabolic severity scores were derived using gender, ethnicity, height, weight, waist circumference, systolic blood pressure, fasting glucose, HDL, and triglyceride values. In people living with obesity, those with prediabetes and T2DM had increased metabolic dysregulation and decreased vitamin C status relative to those without diabetes (P < .05). Vitamin C deficiency was observed in a high proportion (23%-32%) of participants with prediabetes and T2DM and ≥50% had hypovitaminosis C. However, there was no difference in vitamin C intake between those without diabetes and those with prediabetes or T2DM (P > .05). There was a significant inverse correlation between plasma vitamin C status and metabolic severity score (r = -0.290, P < .001). Linear regression indicated that for every 1-unit increase in metabolic severity score, there was a 6.5 µmol/L decrease in vitamin C status. Thus, the enhanced metabolic dysregulation observed with prediabetes and T2DM is associated with an increased demand for vitamin C in people living with obesity.