Vitamin D Status in Young Medical Residents

Evaluation of Vitamin D Status in Young Medical Residents at the Reina Sofia University Hospital in Cordoba

Retrospective, observational, and anonymous study to assess vitamin D status in young medical residents of both sexes who joined the staff of the Reina Sofia University Hospital (HURS) in Cordoba, Spain, in March 2020. Subjects with vitamin D deficiency were treated with calcifediol and reevaluated. The retrospective cohort study was approved (October 29, 2025) by the Provincial Committee on Ethics in Drug Research (CEIm) of Córdoba (Spain), [committee reference number 6337) Communication/application code: SICEIA-2025-002858]. Data Based on the files of the HURS occupational medicine service.

Study Overview

• Status: Completed
• Conditions: Vitamin D Deficiency
• Intervention / Treatment: Drug: Calcifediol (Vitamin D)

Detailed Description

Vitamin D deficiency, expressed as circulating levels of 25-hydroxyvitamin D (25OHD), the sum of 25OHD2 and 25OHD3, is highly prevalent worldwide. Regardless of geographical location and climate, 88% of the world's population has serum 25OHD concentrations below 30 ng/ml; 37% have values below 20 ng/ml and up to 7% have levels below 10 ng/ml. In all regions of Spain, there is a prevalence of vitamin D deficiency similar to that in the rest of the world, which is also high in patients undergoing treatment for osteoporosis. All studies of different population and age subgroups, such as those grouped in the Asturias and Pizarra (Málaga) cohorts, as reported in a recent review , support this fact. It should be noted that the prevalence of 25OHD deficiency is high in winter, even in southern provinces of Spain .

High levels of hypovitaminosis D have been reported in young, healthy adults, medical residents beginning their specialisation training at the Doce de Octubre Hospital in Madrid (Spain), where the majority, aged between 21 and 41, suffered from vitamin D deficiency or insufficiency. Studies with similar characteristics reveal similar data worldwide. A review by McKenna of 117 studies published between 1971 and 1990 on vitamin D concentrations in 27 different regions of the world, 42 of them in young adults, revealed that more than 40% of young adults in Western and Central Europe suffered from vitamin D deficiency during the winter. A study conducted in Boston with healthcare workers aged 18-49 revealed serum concentrations of 25OHD < 20ng/ml in 36% of subjects aged 18-29 at the end of winter (March and April). Another study conducted on internal medicine residents at a hospital in Portland, Oregon, with an average age of 30.1 years for women and 30.6 years for men, revealed 25OHD levels < 20ng/ml in 47% of resident doctors during the months of March and April, and 74% of participants had lower serum 25OHD concentrations in spring than in autumn.

Resident doctors who joined HURS in the spring of 2020 may be vulnerable to low 25OHD levels due to long hours of study preparing for competitive examinations, compounded by lockdown and the subsequent lack of exposure to sunlight The hospital's Occupational Medicine Service assessed vitamin D (25OHD) levels to identify vitamin D deficiency. This deficiency can have functional repercussions in addition to its effects on musculoskeletal metabolism and the innate and adaptive immune systems, among other important functional repercussions. Treatment with calcifediol was initiated in those with deficiencies with the aim of normalising serum 25OHD levels.

Calcifediol offers pharmacokinetic advantages that give it a certain functional superiority over native vitamin D3. It is highly hydrophilic and, therefore, after oral ingestion, it is absorbed through the portal venous system and does not require hydroxylation at position 25, which immediately increases the optimal circulating concentrations of 25(OH)D3. Therefore, when administered orally, it is available in high concentrations within a few hours, and in a stable form, to be a substrate for the synthesis of calcitriol in the kidney and other target organs.

This is not a patient registry. This study is a retrospective observational cohort analysis based on existing occupational health records. No prospective data collection or registry infrastructure was established

• Study Type: Observational
• Enrollment (Actual): 30

Contacts and Locations

Study Locations

• Spain
  • Córdoba, Spain, 14004
    • Hospital Universitario Reina Sofía, Edificio IMIBIC, Avd. Menedez Pidal, s/n

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Medical residents admitted to the Reina Sofia University Hospital Residency Program

Description

Inclusion Criteria:

• Physicians admitted to the Residency Programme at Reina Sofía University Hospital

Exclusion Criteria:

• Subjects for whom there is no data collected in the occupational medicine medical recordrds

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Vitamin D endocrine system	Assess the status of the vitamin D endocrine system	Change from Baseline in the 25OH vitamin D through study completion, an average of 1 year

Collaborators and Investigators

• Sponsor: Maimónides Biomedical Research Institute of Córdoba
• Collaborators: Hospital Universitario Reina Sofia de Cordoba

Publications and helpful links

General Publications

• Quesada-Gomez JM, Bouillon R. Is calcifediol better than cholecalciferol for vitamin D supplementation? Osteoporos Int. 2018 Aug;29(8):1697-1711. doi: 10.1007/s00198-018-4520-y.
• Bouillon R, Quesada Gomez JM. Comparison of calcifediol with vitamin D for prevention or cure of vitamin D deficiency. J Steroid Biochem Mol Biol. 2023 Apr; 228:106248. doi: 10.1016/j.jsbmb.2023.106248.
• Bouillon R, Marcocci C, Carmeliet G, Bikle D, White JH, Dawson-Hughes B, Lips P, Munns CF, Lazaretti-Castro M, Giustina A, Bilezikian J. Skeletal and Extraskeletal Actions of Vitamin D: Current Evidence and Outstanding Questions. Endocr Rev. 2019 Aug 1;40(4):1109-1151. doi: 10.1210/er.2018-00126.
• Haney EM, Stadler D, Bliziotes MM. Vitamin D insufficiency in internal medicine residents. Calcif Tissue Int. 2005 Jan;76(1):11-6. doi: 10.1007/s00223-004-0025-0.
• Tangpricha V, Pearce EN, Chen TC, Holick MF. Vitamin D insufficiency among free-living healthy young adults. Am J Med. 2002 Jun 1;112(8):659-62. doi: 10.1016/s0002-9343(02)01091-4.
• McKenna MJ. Differences in vitamin D status between countries in young adults and the elderly. Am J Med. 1992 Jul;93(1):69-77. doi: 10.1016/0002-9343(92)90682-2.
• Calatayud M, Jódar E, Sánchez R, Guadalix S, Hawkins F. Prevalencia de concentraciones deficientes e insuficientes de vitamina D en una población joven y sana Endocrinol Nutr. 2009 Apr;56(4):164-9. doi: 10.1016/S1575-0922(09)70980-5.
• Mata-Granados JM, Luque de Castro MD, Quesada Gomez JM Niveles séricos inadecuados de retinol, α-tocoferol, 25 hidroxivitamina D3 y 24,25 dihidroxivitamina D3 en adultos españoles sanos: valoración simultánea por HPLC. Clin. Biochem. 2008; 41 : 676-680. doi: 10.1016 / j.clinbiochem.2008.02.00
• Navarro Valverde C, Quesada Gómez JM. Deficiencia de vitamina D en España. ¿Realidad o mito? Rev Osteoporos Metab Miner 2014; 6 (Supl1):S5-10 doi: 10.4321/S1889-836X2014000500002.
• Gómez-Alonso C, Naves-Díaz ML, Fernández-Martín JL, Díaz-López JB, Fernández-Coto MT, Cannata-Andía JB. Vitamin D status and secondary hyperparathyroidism: the importance of 25-hydroxyvitamin D cut-off levels. Kidney Int Suppl. 2003 Jun;(85):S44-8. doi: 10.1046/j.1523-1755.63.s85.11.x.
• González-Molero I, Morcillo S, Valdés S, Pérez-Valero V, Botas P, Delgado E, Hernández D, Olveira G, Rojo G, Gutierrez-Repiso C, Rubio-Martín E, Menéndez E, Soriguer F. Vitamin D deficiency in Spain: a population-based cohort study. Eur J Clin Nutr. 2011; 65: 321-8. doi: 10.1038/ejcn.2010.265.
• Quesada-Gómez JM, Diaz-Curiel M, Sosa-Henriquez M, et al. Low calcium intake and inadequate vitamin D status in postmenopausal osteoporotic women. J Steroid Biochem Mol Biol. 2013; 136: 175-7. doi: 10.1016/j.jsbmb.2012.10.013
• Hilger J, Friedel A, Herr R, et al. A systematic review of vitamin D status in populations worldwide. Br J Nutr. 2014; 111: 23-45. doi: 10.1017/S0007114513001840.
• Giustina A, Bilezikian JP, Adler RA, Banfi G, Bikle DD, Binkley NC, Bollerslev J, Bouillon R, Brandi ML, Casanueva FF, di Filippo L, Donini LM, Ebeling PR, Fuleihan GE, Fassio A, Frara S, Jones G, Marcocci C, Martineau AR, Minisola S, Napoli N, Procopio M, Rizzoli R, Schafer AL, Sempos CT, Ulivieri FM, Virtanen JK. Consensus Statement on Vitamin D Status Assessment and Supplementation: Whys, Whens, and Hows. Endocr Rev. 2024 Sep 12;45(5):625-654. doi: 10.1210/endrev/bnae009.

Study record dates

Study Major Dates

• Study Start (Actual): October 29, 2025
• Primary Completion (Actual): November 1, 2025
• Study Completion (Actual): December 1, 2025

Study Registration Dates

• First Submitted: December 18, 2025
• First Submitted That Met QC Criteria: March 16, 2026
• First Posted (Actual): March 18, 2026

Study Record Updates

• Last Update Posted (Actual): March 18, 2026
• Last Update Submitted That Met QC Criteria: March 16, 2026
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: Vitamin D; Vitamin D3; Cholecalciferol; Calcifediol; Vitamin D endocrine system; VDR Vitamin D; Vitamin D3-sulphate; 25(OH)D3-Sulphate; 25(OH)D- Glucuronide
• Additional Relevant MeSH Terms: Nutrition Disorders; Avitaminosis; Deficiency Diseases; Malnutrition; Nutritional and Metabolic Diseases; Vitamin D Deficiency; Lipids; Polycyclic Compounds; Steroids; Fused-Ring Compounds; Cholestenes; Cholestanes; Sterols; Secosteroids; Membrane Lipids; Hydroxycholecalciferols; Cholecalciferol; Vitamin D; Calcifediol
• Other Study ID Numbers: VitD_6337

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: The information collected will be of public access by request
• IPD Sharing Supporting Information Type: SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No