Vitamin D: State of Knowledge and Optimal Dosing — A Swiss Perspective

Bilingual scientific review (French / English) on vitamin D, with a Swiss focus. This document synthesizes the current state of scientific evidence on vitamin D, integrating major recent randomized controlled trials (VITAL, D2d, DO-HEALTH), landmark meta-analyses (Martineau, 2017), and Swiss epidemiological data (Benhamou, 2021; Patriota, 2022; Kingston, 2024). It is based on 25 references individually verified on PubMed (NIH / NLM). Eleven chapters cover: metabolism and physiology, status assessment (25(OH)D marker and thresholds), Swiss epidemiology, optimal dosing, clinical benefits, the DO-HEALTH trial led from Zurich, safety, practical recommendations adapted to the Swiss context, controversies, and research perspectives. Key Swiss figures: 51% of Basel inpatients with 25(OH)D < 50 nmol/L (Benhamou et al., 2021, n=8,861); 82.1% deficiency in orthopaedic patients before elective surgery (Kingston et al., 2024); approximately CHF 90 million annual cost of vitamin D screening for mandatory insurance in 2018 (Essig et al., 2020); the DO-HEALTH trial led from Zurich (Bischoff-Ferrari et al., JAMA 2020, n=2,157). Available versions: French (vitamine_d_zenodo.pdf, 38 pages) and English (vitamin_d_zenodo_en.pdf, 37 pages). Both versions share identical scientific content and were subjected to an independent Chain-of-Verification (CoVe) audit with 100% conformity to PubMed-indexed primary sources. Conflicts of interest disclosure: The author is the founder of Swilab, a Swiss dietary supplements company. This document was prepared for informational and educational purposes only, without promotional or commercial intent. It does not cite, recommend, or promote any product, brand, or formulation, including those of Swilab. All recommendations are based on internationally recognized guidelines (Endocrine Society 2024) and independent clinical studies published and indexed in PubMed. AI use disclosure: In accordance with current editorial recommendations on scientific transparency, the author declares having used a generative artificial intelligence assistant to support writing and document structuring.