{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T12:59:22Z","timestamp":1786971562261,"version":"build-2736575974"},"reference-count":29,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2021,6,9]],"date-time":"2021-06-09T00:00:00Z","timestamp":1623196800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>Background: The main source of vitamin D is skin synthesis, which depends on sunlight exposure. During the pandemic, COVID-19 children were obliged to home confinement, which potentially limiting sunlight exposure. The aim of this study was to evaluate whether home confinement led to decreased vitamin D serum levels in children in Warsaw, Poland. Methods: The study included 1472 children who were divided into two groups, based on the date of 25(OH)D level blood sampling: before and during the pandemic. Children under 1 year of age (infants) were analysed separately. Results: A statistically significant decrease in the average level of vitamin D was observed between groups of children over 1 year of age (35 ng\/mL \u00b1 18 vs. 31 ng\/mL \u00b1 14). In infants from both groups, the mean vitamin D levels were within the normal range (Group 1 inf 54 ng\/mL \u00b1 21 vs. Group 2 inf 47 ng\/mL \u00b1 15). The characteristic seasonal variability was observed before the pandemic, with maximal vitamin D levels in summer (40 ng\/mL \u00b1 17) and minimal levels in winter (30 ng\/mL \u00b1 14). During the pandemic, no seasonal variability was observed (summer 30 ng\/mL \u00b1 11 vs. winter 30 ng\/mL \u00b1 19). Conclusions: The COVID-19 pandemic restrictions led to a significant decrease in vitamin D serum levels in children.<\/jats:p>","DOI":"10.3390\/nu13061990","type":"journal-article","created":{"date-parts":[[2021,6,9]],"date-time":"2021-06-09T14:16:04Z","timestamp":1623248164000},"page":"1990","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["The Impact of COVID-19 Pandemic during 2020\u20132021 on the Vitamin D Serum Levels in the Paediatric Population in Warsaw, Poland"],"prefix":"10.3390","volume":"13","author":[{"given":"Agnieszka","family":"Rustecka","sequence":"first","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Justyna","family":"Maret","sequence":"additional","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ada","family":"Drab","sequence":"additional","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michalina","family":"Leszczy\u0144ska","sequence":"additional","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3255-7623","authenticated-orcid":false,"given":"Agata","family":"Tomaszewska","sequence":"additional","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Agnieszka","family":"Lipi\u0144ska-Opa\u0142ka","sequence":"additional","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Agata","family":"B\u0119dzichowska","sequence":"additional","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1606-5100","authenticated-orcid":false,"given":"Boles\u0142aw","family":"Kalicki","sequence":"additional","affiliation":[{"name":"Pediatric, Nephrology and Allergology Clinic, Military Institute of Medicine, 04-141 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2772-5127","authenticated-orcid":false,"given":"Jacek Z.","family":"Kubiak","sequence":"additional","affiliation":[{"name":"Cell Cycle Group, Faculty of Medicine, Institute of Genetics and Development of Rennes, University of Rennes 1, 35000 Rennes, France"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,6,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"54","DOI":"10.5114\/pedm.2019.85814","article-title":"Seasonality of Vitamin D Concentrations and the Incidence of Vitamin D Deficiency in Children and Adolescents from Central Poland","volume":"25","author":"Stawerska","year":"2019","journal-title":"Pediatr. Endocrinol. Diabetes Metab."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"111","DOI":"10.3390\/nu5010111","article-title":"Vitamin D-Effects on Skeletal and Extraskeletal Health and the Need for Supplementation","volume":"5","author":"Wacker","year":"2013","journal-title":"Nutrients"},{"key":"ref_3","first-page":"455","article-title":"Calcium and Vitamin D Supply in Polish Population\u2014Facts and Myths","volume":"21","year":"2014","journal-title":"Ann. Agric. Environ. Med."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1678","DOI":"10.1093\/ajcn\/80.6.1678S","article-title":"Sunlight and Vitamin D for Bone Health and Prevention of Autoimmune Diseases, Cancers, and Cardiovascular Disease","volume":"80","author":"Holick","year":"2018","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"226","DOI":"10.1007\/s13668-020-00322-4","article-title":"Role of Vitamins in Skin Health: A Systematic Review","volume":"9","author":"Dattola","year":"2020","journal-title":"Curr. Nutr. Rep."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1007\/s11154-017-9424-1","article-title":"The Vitamin D Deficiency Pandemic: Approaches for Diagnosis, Treatment and Prevention","volume":"18","author":"Holick","year":"2017","journal-title":"Rev. Endocr. Metab. Disord."},{"key":"ref_7","first-page":"2015","article-title":"The Impact of Seasonality and Other Determinants on Vitamin D Concentration in Childhood and Adulthood: Still an Unresolved Issue","volume":"4","author":"Lippi","year":"2016","journal-title":"Ann. Transl. Med."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1","DOI":"10.3389\/fendo.2018.00373","article-title":"Rationale and Plan for Vitamin D Food Fortification: A Review and Guidance Paper","volume":"9","author":"Pilz","year":"2018","journal-title":"Front. Endocrinol."},{"key":"ref_9","unstructured":"(2021, April 24). World Health Organization Coronavirus Disease (COVID-19) Situation-Report-51. Available online: https:\/\/www.who.int\/docs\/default-source\/coronaviruse\/situation-reports\/20200311-sitrep-51-covid-19.pdf?sfvrsn=1ba62e57_10."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Bartoszek, A., Walkowiak, D., Bartoszek, A., and Kardas, G. (2020). Mental Well-Being (Depression, Loneliness, Insomnia, Daily Life Fatigue) during COVID-19 Related Home-Confinement\u2014A Study from Poland. Int. J. Environ. Res. Public Health, 17.","DOI":"10.3390\/ijerph17207417"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1","DOI":"10.3389\/fendo.2018.00246","article-title":"Vitamin D Supplementation Guidelines for General Population and Groups at Risk of Vitamin D Deficiency in Poland\u2014Recommendations of the Polish Society of Pediatric Endocrinology and Diabetes and the Expert Panel with Participation of National Specialist C","volume":"9","author":"Rusinska","year":"2018","journal-title":"Front. Endocrinol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2669","DOI":"10.2147\/RMHP.S282495","article-title":"Effect of Pandemic-Related Confinement on Vitamin D Status among Children Aged 0\u20136 Years in Guangzhou, China: A Cross-Sectional Study","volume":"13","author":"Yu","year":"2020","journal-title":"Risk Manag. Healthc. Policy"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"667","DOI":"10.1530\/EC-17-0193","article-title":"Variations in Infant and Childhood Vitamin D Supplementation Programmes across Europe and Factors Influencing Adherence","volume":"6","author":"Uday","year":"2017","journal-title":"Endocr. Connect."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1041","DOI":"10.1515\/jpem-2017-0132","article-title":"Do Sufficient Vitamin D Levels at the End of Summer in Children","volume":"30","author":"Shakeri","year":"2017","journal-title":"J. Pediatr. Endocrinol. Metab."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Hansen, L., Tj\u00f8nneland, A., K\u00f8ster, B., Brot, C., Andersen, R., Cohen, A.S., Frederiksen, K., and Olsen, A. (2018). Vitamin D Status and Seasonal Variation among Danish Children and Adults: A Descriptive Study. Nutrients, 10.","DOI":"10.3390\/nu10111801"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/1824-7288-40-54","article-title":"Prevalence of Hypovitaminosis D and Predictors of Vitamin D Status in Italian Healthy Adolescents","volume":"40","author":"Vierucci","year":"2014","journal-title":"Ital. J. Pediatr."},{"key":"ref_17","first-page":"10","article-title":"Lifestyle and Body Weight Consequences of the COVID-19 Pandemic in Children: Increasing Disparity","volume":"1","author":"Koletzko","year":"2021","journal-title":"Ann. Nutr. Metab."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1111\/ijpo.12731","article-title":"Changes in Lifestyle Behaviours during the COVID-19 Confinement in Spanish Children: A Longitudinal Analysis from the MUGI Project","volume":"16","author":"Medrano","year":"2021","journal-title":"Pediatr. Obes."},{"key":"ref_19","first-page":"1","article-title":"Health-Related Behaviors Among School-Aged Children and Adolescents During the Spanish Covid-19 Confinement","volume":"8","author":"Calatayud","year":"2020","journal-title":"Front. Pediatr."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Sidor, A., and Rzymski, P. (2020). Dietary Choices and Habits during COVID-19 Lockdown: Experience from Poland. Nutrients, 12.","DOI":"10.3390\/nu12061657"},{"key":"ref_21","first-page":"1","article-title":"Systematic Review of the Literature About the Effects of the COVID-19 Pandemic on the Lives of School Children","volume":"11","year":"2020","journal-title":"Front. Psychol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1","DOI":"10.3389\/fpsyt.2020.570164","article-title":"Psychological Symptoms and Behavioral Changes in Children and Adolescents During the Early Phase of COVID-19 Quarantine in Three European Countries","volume":"11","author":"Francisco","year":"2020","journal-title":"Front. Psychiatry"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Martineau, A.R., Jolliffe, D.A., Hooper, R.L., Greenberg, L., Aloia, J.F., Bergman, P., Dubnov-Raz, G., Esposito, S., Ganmaa, D., and Ginde, A.A. (2017). Vitamin D Supplementation to Prevent Acute Respiratory Tract Infections: Systematic Review and Meta-Analysis of Individual Participant Data. BMJ, 356.","DOI":"10.1136\/bmj.i6583"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"3595","DOI":"10.1002\/ppul.25106","article-title":"Is Vitamin D Deficiency a Risk Factor for COVID-19 in Children?","volume":"55","year":"2020","journal-title":"Pediatr. Pulmonol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1007\/s40618-020-01327-0","article-title":"Possible Role of Vitamin D in Covid-19 Infection in Pediatric Population","volume":"44","author":"Panfili","year":"2021","journal-title":"J. Endocrinol. Investig."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2492","DOI":"10.2174\/1381612826666200310145935","article-title":"Vitamin D and Sleep Regulation: Is there a Role for Vitamin D?","volume":"26","author":"Romano","year":"2020","journal-title":"Curr. Pharm. Des."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Barrea, L., Frias-Toral, E., Pugliese, G., Garcia-Velasquez, E., Carignano, M.D.L.A., Savastano, S., Colao, A., and Muscogiuri, G. (2020). Vitamin D in obesity and obesity-related diseases: An overview. Minerva Endocrinol., 2020.","DOI":"10.23736\/S2724-6507.20.03299-X"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1007\/s00204-016-1804-x","article-title":"Vitamin D and chronic diseases: The current state of the art","volume":"91","author":"Muscogiuri","year":"2017","journal-title":"Arch. Toxicol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"850","DOI":"10.1038\/s41430-020-0635-2","article-title":"Nutritional recommendations for CoVID-19 quarantine","volume":"74","author":"Muscogiuri","year":"2020","journal-title":"Eur. J. Clin. Nutr."}],"container-title":["Nutrients"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-6643\/13\/6\/1990\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:12:40Z","timestamp":1760163160000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-6643\/13\/6\/1990"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,6,9]]},"references-count":29,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2021,6]]}},"alternative-id":["nu13061990"],"URL":"https:\/\/doi.org\/10.3390\/nu13061990","relation":{},"ISSN":["2072-6643"],"issn-type":[{"value":"2072-6643","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,6,9]]}}}