Effect of Vitamin D3 Supplementation Combined with Exercise Training on Glycemic Control and Bone Health in Patients with Type 2 Diabetes: A Randomized, Placebo-Controlled Trial

Aims This study aimed to examine the effect of a 12-week vitamin D supplementation and exercise training alone and in combination on glycemic control and bone health in Chinese type 2 diabetes patients.MethodsSixty-one type 2 diabetes patients (age, 33–65 years; 72.0% men) with non-insulin dependence were randomized into the 12-week vitamin D group (1000 IU/day), exercise group (60%–80% of maximal heart rate, 1 h/time, 2–3 times/week), vitamin D combined with exercise group, and control group. A 75-g oral glucose tolerance test was used to estimate glycemic control. Dual X-ray absorptiometry was used to examine bone health (bone mass content and bone mass density) and body fat percentage (%).Results During the 75-g oral glucose tolerance test, lower glucose and higher insulin levels were found in the vitamin D combined with exercise group, vitamin D group, and exercise group after intervention than before intervention, although the differences were not statistically significant. A significant exercise and vitamin D interaction for the insulinogenic index (P = 0.032) and a borderline interaction for the glucose disposition index (P = 0.051) were observed, while no further independent effect was observed. Compared with non-vitamin D supplementation, vitamin D supplementation significantly alleviated the loss of total bone mass content (95% CI: -29.9–19.4 vs. -74.9–-24.7), trunk bone mass content (95% CI: -24.1–19.5 vs. -56.1–-11.7), and spine bone mass density (95% CI: -0.03–0.03 vs. -0.07–-0.01).ConclusionsThe findings suggest that 12-week combined vitamin D and exercise intervention has a potentially positive effect on glycemic control, and vitamin D supplementation plays an important role in the prevention of bone loss, which was identified in the exercise alone group. Further studies are needed to elucidate the long-term effect of combined vitamin D and exercise intervention in type 2 diabetes patients.The study was registered in the Chinese Clinical Trial System (No. ChiCTR1800015383).