Low serum concentrations of 25-hydroxyvitamin D [25(OH)D] have been associated with impaired glucose tolerance and diabetes. 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). 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 D(3) and 150 mg Ca/250 mL), or vitamin D + calcium-fortified yogurt drink (DCY; containing 500 IU vitamin D(3) 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. In both the DY and DCY groups, mean serum 25(OH)D(3) 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). 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.

Background: Endothelial dysfunction has been proposed as the underlying cause of diabetic angiopathy that eventually leads to cardiovascular disease, the major cause of death in diabetes. We recently demonstrated the ameliorating effect of regular vitamin D intake on the glycemic status of patients with type 2 diabetes (T2D). In this study, the effects of improvement of vitamin D status on glycemic status, lipid profile and endothelial biomarkers in T2D subjects were investigated. Methods: Subjects with T2D were randomly allocated to one of the two groups to receive either plain yogurt drink (PYD; containing 170 mg calcium and no vitamin D/250 mL, n₁ = 50) or vitamin D3-fortified yogurt drink (FYD; containing 170 mg calcium and 500 IU/250 mL, n₂ = 50) twice a day for 12 weeks. Anthropometric measures, glycemic status, lipid profile, body fat mass (FM) and endothelial biomarkers including serum endothelin-1, E-selectin and matrix metalloproteinase (MMP)-9 were evaluated at the beginning and after the 12-week intervention period. Results: The intervention resulted in a significant improvement in fasting glucose, the Quantitative Insulin Check Index (QUICKI), glycated hemoglobin (HbA1c), triacylglycerols, high-density lipoprotein cholesterol (HDL-C), endothelin-1, E-selectin and MMP-9 in FYD compared to PYD (P < 0.05, for all). Interestingly, difference in changes of endothelin-1, E-selectin and MMP-9 concentrations in FYD compared to PYD (-0.35 ± 0.63 versus -0.03 ± 0.55, P = 0.028; -3.8 ± 7.3 versus 0.95 ± 8.3, P = 0.003 and -2.3 ± 3.7 versus 0.44 ± 7.1 ng/mL, respectively, P < 0.05 for all), even after controlling for changes of QUICKI, FM and waist circumference, remained significant for endothelin-1 and MMP-9 (P = 0.009 and P = 0.005, respectively) but disappeared for E-selectin (P = 0.092). On the contrary, after controlling for serum 25(OH)D, the differences disappeared for endothelin-1(P = 0.066) and MMP-9 (P = 0.277) but still remained significant for E-selectin (P = 0.011). Conclusions: Ameliorated vitamin D status was accompanied by improved glycemic status, lipid profile and endothelial biomarkers in T2D subjects. Our findings suggest both direct and indirect ameliorating effects of vitamin D on the endothelial biomarkers. Trial registration: ClinicalTrials.gov: NCT01236846

Systemic inflammation is thought to have a central role in diabetic long-term complications. The aim of this study was to investigate the effects of vitamin D either with or without extra calcium on certain inflammatory biomarkers in the subjects with type 2 diabetes (T2D). This was a double-blind, randomized, controlled trial conducted over 12 wk in 90 T2D subjects aged 30-60 yr from both sexes. Subjects were randomly allocated to one of three groups to receive two 250-ml bottles a day of plain Persian yogurt drink or doogh (PD, containing 150 mg calcium and no detectable vitamin D(3)/250 ml), vitamin D-fortified doogh (DD, containing 500 IU vitamin D(3) and 150 mg calcium/250 ml), or calcium + vitamin D(3)-fortified doogh (CDD, containing 500 IU vitamin D(3) and 250 mg calcium/250 ml). The changes in inflammatory markers were evaluated. Compared to the baseline values, highly sensitive C-reactive protein, IL-1β, IL-6, fibrinogen, and retinol binding protein-4 concentrations significantly decreased in both the DD and CDD groups. Although the decrement in highly sensitive C-reactive protein and fibrinogen was more in CDD compared to DD (-4.0 ± 8.5 vs. -1.3 ± 2.8 mg/liter, and -0.40 ± 0.74 and -0.20 ± 0.52 mg/liter, respectively), the differences were not significant. There was a significant increase in serum adiponectin in both the DD and CDD groups (51.3 ± 65.3 vs. 57.1 ± 33.8 μg/liter; P < 0.05). Mean adiponectin changes in CDD were significantly higher than in PD (P = 0.021). Daily intake of vitamin D-fortified doogh improved inflammatory markers in T2D subjects, and extra calcium conferred additional benefit only for the antiinflammatory adipokine, i.e. adiponectin.