Daily intake of vitamin D‐ or calcium‐vitamin D‐fortified Persian yogurt drink (doogh) attenuates diabetes‐induced oxidative stress: evidence for antioxidative properties of vitamin D

BACKGROUND: Both poor vitamin D status and oxidative stress (OS) have been independently associated with late diabetic complications, including cardiovascular disease (CVD). The present study aimed to examine the effect of daily intake of vitamin D alone or in combination with calcium as a fortified Persian yogurt drink (doogh) on OS over 12 weeks. METHODS: Ninety patients with type 2 diabetes aged 30–50 years from both sexes were randomly allocated to one of the three groups to receive two 250‐mL bottles of doogh a day, which was either plain (PD; containing 150 mg per 250 mL of calcium and no detectable vitamin D), vitamin D‐fortified (DD; containing 150 mg of calcium + 500 IU vitamin D per 250 mL) or calcium‐vitamin D‐fortified (CDD; 250 mg od calcium + 500 IU vitamin D per 250 mL). RESULTS: Although mean (SD) serum concentrations of protein carbonyl significantly decreased in both DD and CDD groups [−2.07 (4.39) nm, P = 0.015 and −4.4 (7.64) nm, P = 0.003, respectively], the change in PD group was not significant [−0.54 (6.96) nm, P = 0.674]. A similar pattern was observed for cardiac myeloperoxidase [PD: −19.4 (75.9) μg L⁻¹, P = 0.173; DD: −21.8 (54.2) μg L⁻¹, P = 0.035, CDD: −48.5 (76.9) μg L⁻¹, P = 0.002]. Superoxide dismutase increased significantly only in DD and CDD [56.9 (74.0) U L⁻¹, P < 0.001 and 51.6 (119.9) U L⁻¹, P = 0.025, respectively]. Changes of serum advanced glycation end‐products showed a significant between‐group difference among PD, DD and CDD [239.4 (388.4) U L⁻¹, −58.1 (147.6) U L⁻¹and −143.7 (475.9) U L⁻¹ × 10³, respectively, P = 0.003], which remained significant after controlling for changes of fasting serum glucose (P = 0.013) and glycated haemoglobin (P = 0.015). CONCLUSIONS: The findings of the present study demonstrated an OS attenuating effect of vitamin D. However, extra calcium did not convey additional benefit.