Interpretation of vitamin D status in clinical guidelines: unity and contradictions

Background. Currently, the criteria for vitamin D deficiency, as well as the recommended doses for its intake, remain controversial. The variety of recommendations for the intake of cholecalciferol are associated with different purposes of use: obtaining a sufficient daily intake, preventing rickets and osteomalacia, reducing the risk of fractures, or reducing cardiovascular risks and mortality. There are also controversial issues regarding the classification of vitamin D status and the terminology associated with the serum 25(OH)D concentration. The current classification of vitamin D status does not take into account changes in individual sensitivity to the action of vitamin D, which may be attributable to genetic, epigenetic, nutritional factors, concomitant diseases, or medications. Despite the active study and implementation of D-deficiency prevention, the prevalence of vitamin D deficiency remains high in the Russian Federation, including in young people.

Objective. Evaluation of the dynamics of the blood serum 25(OH)D level in young people without chronic and acute diseases aged 18 to 35 years while taking cholecalciferol preparations.

Materials and methods: 84 people aged 18 to 35 years were examined, including 49 (58.3%) men and 35 (41.7%) women with vitamin D deficiency. All participants with vitamin D deficiency were recommended cholecalciferol at a dose of 5000–7000 IU/day, depending on the level of D-deficiency for 3 months to replenish (“saturate”) the deficiency. Determination of blood serum 25(OH)D level was performed by the immunochemical analysis method upon inclusion in the study, and then after 3 and 6 months (if necessary) while taking cholecalciferol. The study was conducted from 03/09/2023 to 05/06/2024.

Results. After 3 months of «saturation therapy», 75% of participants (63 of 84) achieved the target blood level of vitamin D (≥30 ng/ml), including 38 (77.55%) men and 23 (65.71%) women. After 6 months of treatment, 68 (80.96%) participants achieved the target blood level of vitamin D (≥30 ng/ml, including 43 (87.76%) men and 25 (71.43%) women. Replenishment of vitamin D deficiency with saturating doses of cholecalciferol was generally effective. In men, the dynamics of D-deficiency treatment was more favorable than in women: the average blood vitamin D level increased from 13.13 to 35.33 ng/ml, an increase of 257%; in women, the average blood vitamin D level increased from 5.45 to 32.16 ng/ml, an increase of 122%. Student’s t-test for independent samples showed that the differences in the dynamics of vitamin D deficiency treatment between men and women are statistically significant (t=2.62; p=0.01). However, not all study participants achieved the adopted target levels, which suggests that an individual approach with the selection of the dose and duration of «saturation therapy» will be required.

Conclusion. In general, loading doses of cholecalciferol in most people contribute to the restoration of vitamin D levels in case of its initial deficiency. However, there are those who do not achieve the adopted target values when taking saturating doses of cholecalciferol. Probably, in such cases a personalized approach with individual selection of the dose and duration of treatment taking into account various factors are required.