Daily consumption of vitamin D- or vitamin D plus calcium-fortified yogurt drink improved glycemic control in patients with type 2 diabetes: a randomized clinical trial

Background: Low serum concentrations of 25-hydroxyvitamin D [25(OH)D] have been associated with impaired glucose tolerance and diabetes. Objective: This study aimed to compare the effects of daily intake of vitamin D-or vitamin D-3 + calcium-fortified yogurt drink on glycemic status in subjects with type 2 diabetes (T2D). Design: Ninety diabetic subjects were randomly allocated to 3 groups to consume plain yogurt drink (PY; containing no vitamin D and 150 mg Ca/250 mL), vitamin D-fortified yogurt drink (DY; containing 500 IU vitamin D3 and 150 mg Ca/250 mL), or vitamin D + calcium-fortified yogurt drink (DCY; containing 500 IU vitamin D3 and 250 mg Ca/250 mL) twice per day for 12 wk. Fasting serum glucose (FSG), glycated hemoglobin (Hb A(1c)), homeostasis model assessment of insulin resistance (HOMA-IR), serum lipid profile, and percentage fat mass (FM) were assessed before (baseline) and after the intervention. Results: In both the DY and DCY groups, mean serum 25(OH) D3 improved (+32.8 +/- 28.4 and +28.8 +/- 16.1 nmol/L, respectively; P < 0.001 for both), but FSG [-12.9 +/- 33.7 mg/dL (P = 0.015) and -9.6 +/- 46.9 mg/dL (P = 0.035)], Hb A(1c) [-0.4 +/- 1.2% (P < 0.001) and -0.4 +/- 1.9% (P < 0.001)], HOMA-IR [-0.6 +/- 1.4 (P = 0.001) and -0.6 +/- 3.2 (P < 0.001)], waist circumference (-3.6 +/- 2.7 and -2.9 +/- 3.3; P < 0.001 for both), and body mass index [in kg/m(2); -0.9 +/- 0.6 (P < 0.001) and -0.4 +/- 0.7 (P = 0.005)] decreased significantly more than in the PY group. An inverse correlation was observed between changes in serum 25(OH) D-3 and FSG (r = -0.208, P = 0.049), FM (r = -0.219, P = 0.038), and HOMA-IR (r = -0.219, P = 0.005). Conclusion: Daily intake of a vitamin D-fortified yogurt drink, either with or without added calcium, improved glycemic status in T2D patients. This trial was registered at clinicaltrials.gov as NCT01229891. Am J Clin Nutr 2011;93:764-71.