The Effect of Vitamin D Supplementation on Ankle-brachial Index in Patients with Type 2 Diabetes: A Randomized Clinical Trial.

Background: Vitamin D deficiency in patients with type 2 diabetes (T2D) is recognized as a risk factor for developing vascular complications and poor disease control. This study aimed to determine the effect of vitamin D supplementation on ankle-brachial index (ABI) in patients with T2D.

Materials and methods: This two-group clinical trial was conducted among 56 patients with T2D. Participants were recruited through sampling conducted in the diabetes clinic of Velayat Hospital in Qazvin, Iran. They were allocated to the intervention and control groups using a simple blocked randomization method. The intervention group received an oral dose of 1000 IU/day of vitamin D. Data were collected using a checklist that included demographic information, laboratory measurements, and ABI.

Results: After the intervention, the score in the intervention group (ABI < 0.9: t₃₂ = 4.082, p < 0.001) was significantly different from the control group (ABI ≥ 1.3: t₂₀ = -2.711, p = 0.013). After the intervention, significant differences were also observed regarding the mean ranges of vitamin D (t₅₄ = 10.07, p < 0.001), fasting blood glucose (FBG) (t₅₄ = -2.97, p = 0.004), 2-hour post-prandial blood glucose (2hpp) (t₅₄ = -2.55, p = 0.013), and hemoglobin A1c (HbA1c) (t₅₄ = -3.02, p = 0.004) between the two groups.

Conclusions: The results of this study revealed that a daily intake of 1000 IU of vitamin D significantly improved the ABI, serum concentration of vitamin D, FBG, and HbA1c in patients with T2D. These findings suggest that vitamin D supplementation may be considered an effective approach for preventing arterial diseases and improving blood sugar control.