Seasonal Variation of Vitamin D via Several Parameters in Adolescents

Abstract

Aim:Vitamin D in adolescents reveals that subclinical vitamin D deficiency is continuously increasing worldwide. The aim of this study was to investigate the prevalence of vitamin D and subclinical vitamin D deficiency and risk factors among adolescents in the summer and winter seasons in İzmir.Materials and Methods:The medical records of 90 adolescents were reviewed regarding their vitamin D status in the summer and winter seasons. Blood samples were obtained from 90 adolescents at the end of summer and the end of winter. These samples were assessed for calcium (Ca++), phosphorus, magnesium (Mg), parathyroid hormone, alkaline phosphatase and 25-hydroxyvitamin D concentrations. The subjects were divided into two groups; the first group consisted of the patients who were assessed for vitamin D levels and the other laboratory measurements at the end of winter (n=46), the second group consisted of the patients who were assessed for the same laboratory features at the end of summer (n=44). The two groups were compared in terms of demographic, clinical and laboratory characteristics.Results:Among the 90 patients enrolled in the study, 41 (45.5%) were males and 49 (54.5%) were females. The median age was 11±4 years. Vitamin D deficiency percentages of the study group for the end of the winter period was 60.8% and for the end of the summer period was 6.8% but this was not statistically significant. Vitamin D insufficiency percentages of the winter group were higher than the summer group (93.2% vs. 39.2%, p>0.05). There were no differences between the groups in terms of laboratory findings concerning Ca, Mg and the other bone parameters.Conclusion:Contrary to the expected, we did not detect a seasonal difference in vitamin D levels in adolescents. Although laboratory findings were not found to be statistically significant in terms of vitamin D levels, we can state that the level of vitamin D in the winter season might be lower than the summer season. Therefore, it should be kept in mind that vitamin D insufficiency is more frequent at the end of the winter season and seasonal differences in the adolescent population should be considered during measurement.

Keywords

• Vitamin D
• seasonal variation
• adolescents