Fig. 3

Meta-regression analysis of the effect of vitamin C supplementation on serum cholesterol of type 2 diabetic patients; the influence of covariates patients mean age, duration of supplementation and baseline BMI. As indicated, WMD increases with increment in age, BMI and decrement in duration. The higher reduction was observed in younger type 2 DM patients (β = 2.63, CI 0.22–5.04, p-value = 0.036), longer duration of treatment (β = -1.42, CI − 2.48, − 0.36, p-value = 0.014), and lower BMI (β = 6.92, CI 1.02–12.82, p-value = 0.028)