The inclusion criteria were: (1) RCT design, (2) adult population (age ≥ 18y), (3) population diagnosed with type 2 diabetes, (4) reported at least one glycemic control outcome (FBG or insulin or HbA1c or insulin resistance), (5) insulin resistance estimated by HOMA-IR; ((glucose, [mmol/L] × insulin [mU/L])/22.5) [33], (6) data reported as mean ± SD along with 95%CI,(7) the intervention group provided Vitamin D supplementation, while the control group provided placebo. The gene discussed is INS; the disease is type 2 diabetes mellitus.