{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,4]],"date-time":"2026-09-04T18:07:43Z","timestamp":1788545263170,"version":"build-2803163510"},"reference-count":38,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2021,7,31]],"date-time":"2021-07-31T00:00:00Z","timestamp":1627689600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>Background: There is no consensus regarding vitamin sufficiency status with either 20 ng\/mL or 30 ng\/mL sufficiency cut-off. We assessed the effects of summer sunshine exposure on vitamin D status. Participants: We measured vitamin D concentrations, PTH, creatinine, and total calcium in 132 healthy subjects, age 29.36 \u00b1 13.57 years, in spring and autumn. Results: There was an overall increase in vitamin D concentrations from spring to autumn from 18.1 \u00b1 7.39 ng\/mL to 24.58 \u00b1 7.72 ng\/mL, (p &lt; 0.001), accompanied by a decrease in PTH from 44.4 \u00b1 17.76 pg\/mL to 36.6 \u00b1 14.84 pg\/mL, (p &lt; 0.001). In spring, only 5.3% of individuals were vitamin D sufficient for a 30 ng\/mL cut-off, increasing to 23.2% in autumn (p &lt; 0.001). In contrast, when a 20 ng\/mL cut-off was employed, vitamin D sufficiency was found in 34.1% in spring and 66.4% individuals in autumn, respectively, (p &lt; 0.001). In multiple regression analysis, holiday leave was the only significant determinant of vitamin D increase (p &lt; 0.001). Conclusions: Holiday leave is the strongest determinant of an increase in vitamin D. The majority of healthy individuals fail to reach a 30 ng\/mL vitamin D cut-off after summer sunshine exposure. This raises the question, whether such a cut-off is indeed suitable for the Polish population.<\/jats:p>","DOI":"10.3390\/ijerph18158116","type":"journal-article","created":{"date-parts":[[2021,8,1]],"date-time":"2021-08-01T21:51:07Z","timestamp":1627854667000},"page":"8116","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Effect of Summer Sunshine Exposure on Vitamin D Status in Young and Middle Age Poles: Is 30 ng\/mL Vitamin D Cut-Off Really Suitable for the Polish Population?"],"prefix":"10.3390","volume":"18","author":[{"given":"Magdalena","family":"Basi\u0144ska-Lewandowska","sequence":"first","affiliation":[{"name":"\u201cYour Family Doctor\u201d, General Practice Surgery, 93-324 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrzej","family":"Lewi\u0144ski","sequence":"additional","affiliation":[{"name":"Department of Endocrinology and Metabolic Diseases, Polish Mother\u2019s Memorial Hospital\u2014Research Institute, 93-338 Lodz, Poland"},{"name":"Department of Endocrinology and Metabolic Diseases, Medical University of Lodz, 90-419 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wojciech","family":"Horzelski","sequence":"additional","affiliation":[{"name":"Department of Mathematics and Computer Science, University of Lodz, 90-238 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0019-4269","authenticated-orcid":false,"given":"El\u017cbieta","family":"Skowro\u0144ska-J\u00f3\u017awiak","sequence":"additional","affiliation":[{"name":"Department of Endocrinology and Metabolic Diseases, Polish Mother\u2019s Memorial Hospital\u2014Research Institute, 93-338 Lodz, Poland"},{"name":"Department of Endocrinology and Metabolic Diseases, Medical University of Lodz, 90-419 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,7,31]]},"reference":[{"key":"ref_1","first-page":"83","article-title":"Prevalence of vitamin D deficiency in healthy Iranian children: A systematic review and meta-analysis","volume":"32","author":"Jazayeri","year":"2018","journal-title":"Med. 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