Background and Objectives: The interaction of environmental factors and genetic determines the development of type 2 diabetes (T2D). The objectives were to evaluate the effects of improvement of vitamin D status on the biomarkers of oxidative stress (OS) in T2D subjects and whether vitamin D receptor (VDR)-FokI polymorphism could modulate the response to vitamin D3 intake.

Materials and Methods: Subjects with T2D were allocated to one of the two groups to receive either plain doogh (PD n1= 50) or vitamin D3-fortified doogh (FD, containing 500 IU/250 ml, n= 50) twice a day for 12 weeks. Outcomes were changes in serum 25-hydroxyvitamin D (25(OH)D), superoxide dismutase, glutathione (GSH), total antioxidant capacity (TAC) and malondialdehyde (MDA). VDR genotypes in 140 T2D subjects in FD were determined by FokI restriction enzyme.

Results: After 12 weeks, serum 25(OH)D increased significantly in FD (from 38.5 ± 202.2 to 72.0 ± 23.5, P=0.001) as compared with PD (from 38.8 ± 22.8 to 33.4 ± 22.8, P = 0.28). Comparisons between FD and PD revealed significant differences in changes of serum MDA (-0.54 ± 0.82 µmol/l vs +0.17 ± 1 µmol/l, P=0.001), GSH (+8.4 ± 40.1 ng/l
vs - 13.1 ± 29.4 ng/l, P = 0.002) and TAC (+0.14 ± 0.43 mmol/l vs +0.02 ± 0.45 mmol/l bovine serum albumin equivalent, P = 0.03). Although there was no significant association between FokI genotypes and OS biomarkers, ff variant subgroup showed the weakest response to vitamin D.

Conclusions: Improvement of vitamin D status via daily intake of FD ameliorates OS biomarkers in T2D subjects, and the interactive effect of FokI genotypes cannot be ruled out.