Vitamin D supplement efficacy: Table 3.11 showed that at T6 the mean vitamin D concentration in the intervention group gained 4.23 ± 3.96 ng / ml, at T (6 - 12) gained 1.30 ± 3.87 ng / ml, and after 12 months the mean vitamin D concentration gained 5.54 ± 0.09 ng / ml (all p <0.05).