After the administration of calcium plus vitamin D supplements , we observed a significant reduction in fasting plasma glucose ( -0.89 0.69 vs +0.26 0.92 mmol/l , p < 0.001 ) , serum insulin levels ( -13.55 35.25 vs +9.17 38.50 pmol/l , p = 0.02 ) and HOMA-IR ( -0.91 1.18 vs +0.63 2.01 , p = 0.001 ) and a significant increase in QUICKI ( +0.02 0.03 vs -0.002 0.02 , p = 0.003 ) compared with placebo .