Vitamin D supplementation in obese type 2 diabetes subjects in Ajman, UAE: a randomized controlled double-blinded clinical trial

Randomized, double-blind, placebo-controlled trial in obese, vitamin D-deficient Emirati adults with type 2 diabetes in Ajman, United Arab Emirates. In the active vitamin D group, 45 participants were randomized and 43 were analyzed at the end of the trial; the placebo group had 42 randomized and 39 analyzed.

Vitamin D3 was given as oral unlabelled capsules for 6 months: 6000 IU/day for the first 3 months, then 3000 IU/day for the next 3 months. The active regimen was compared with identical placebo capsules containing starch.

Vitamin D3 corrected vitamin D deficiency biochemically but did not improve glycemic control or lipids. Serum 25(OH)D increased by the end of phase 1 (P = 0.003), then fell in phase 2 (P o0.01) while remaining above baseline (P o0.01), and parathyroid hormone decreased in phase 2 in the vitamin D group (P = 0.003). In contrast, fasting glucose, HbA1c, C-peptide, creatinine, phosphorous, alkaline phosphatase, lipids, C-reactive protein, and thyroid-stimulating hormone did not change significantly in either group.

Modest sample size with attrition from randomization to analysis, limiting power for metabolic outcomes. The trial was single-center, limited to obese vitamin D-deficient Emirati adults with type 2 diabetes, and lasted only 6 months, which reduces generalizability and may be too short to detect longer-term metabolic effects. Usual diet and physical activity were not specifically measured, and background diabetes therapy may have added variability.