Seasonal variation of total and bioavailable 25-hydroxyvitamin D [25(OH)D] in the healthy adult Slovenian population

Osredkar, Joško (author), Vičič, Vid (author), Hribar, Maša (author), Benedik, Evgen (author), Siuka, Darko (author), Jerin, Aleš (author), Čegovnik Primožič, Urška (author), Fabjan, Teja (author), Kumer, Kristina (author), Pravst, Igor (author), Žmitek, Katja (author)

Objective: The aim of our study was to compare the total 25(OH)D fraction, the bioavailable vitamin fraction, and the free vitamin D fraction in spring and fall in a group of healthy individuals. Methods: In our study, we collected blood samples from healthy participants at the end of both summer and winter, and measured serum levels of albumin, DBP, and 25(OH)D. Utilizing these data, we calculated the percentage of free and bioavailable vitamin D. Our cohort comprised 87 participants, with a maleto- female ratio of 14:73, aged 35.95 ± 12.55 years, ranging from 19 to 70 years. We employed the chemiluminescence method to determine the vitamin 25(OH)D levels, the ELISA method was utilized to determine DBP levels, the albumin BCP Assay was performed using the ADVIA biochemical analyzer (Siemens) and an online calculator was used to determine the free and bioavailable 25(OH)D levels. Results: Our findings indicate significantly lower 25(OH)D levels in winter (44.13 ± 17.82 nmol/L) compared to summer (74.97 ± 22.75 nmol/L; p < 0.001). For vitamin D binding protein there was no significant difference from summer (236.2 ± 164.39 mg/L) to winter (239.86 ± 141.9 mg/L; p = 0.77), albumin levels were significantly higher in summer (49.37 ± 4.15 g/L vs. 47.97 ± 3.91 g/L, p = 0.01), but the magnitude of the change may not be large enough to be solely responsible for the stability of vitamin D levels throughout the year. In the winter season a significantly lower calculated bioavailable 25(OH)D vitamin (7.45 ± 5.66 nmol/L against 13.11 ± 8.27 nmol/L; p < 0.001) was observed, and the free fraction also showed a significant decrease (17.3 ± 12.9 pmol/L versus 29.7 ± 19.1 pmol/L; p < 0.0001). We observed a moderately positive correlation between 25(OH)D and bioavailable percentage in winter (r = 0.680; p < 0.001), in contrast with a lower positive association in summer (r = 0.343; p < 0.001). Conclusion: Our data suggest a positive correlation between total and bioavailable 25(OH)D levels. In addition to the statistically significant variation in 25(OH)D between the two observation periods, there was an additional variation in the free vitamin D percentage. The summertime synthesis of vitamin D in the skin could contribute directly to the free fraction of vitamin D. Standardizing the measurement of free 25(OH)D and clinical studies is necessary to establish reference values before these methods can be implemented in clinical practice.

• Language: English
• Keywords: body mass index, ultraviolet, D3, cholecalciferol, D2, ergocalciferol, total 25(OH)D, 25-hydroxycholecalciferol, calcifediol, calcidiol, 25-hydroxyvitamin, 1, 25-(OH)D, 1, 25-dihydroxyvitamin D, vitamin D binding protein, Odds ratio
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FFA - Faculty of Pharmacy; ZF - Faculty of Health Sciences; BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: 13 str.
• Numbering: Vol. 71
• PID: 20.500.12556/RUL-162184
• UDC: 577.161
• ISSN on article: 1734-154X
• DOI: 10.3389/abp.2024.13108
• COBISS.SI-ID: 207062787
• Publication date in RUL: 19.09.2024

Record is a part of a journal

• Title: Acta Biochimica Polonica
• Shortened title: Acta Biochim. Pol.
• Publisher: Committee of Biochemistry and Biophysics. Polish Academy of Sciences, Polish Biochemical Society
• ISSN: 1734-154X
• COBISS.SI-ID: 524433945

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: indeks telesne mase, ultravijolično, D3, holekalciferol, D2, ergokalciferol, skupaj 25(OH)D, 25-hidroksiholekalciferol, kalcifediol, kalcidiol, 25-hidroksivitamin, 1, 25-(OH)D, 1, 25-dihidroksivitamin D, protein, ki veže vitamin D, razmerje kvot, vitamin D