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Schoenmakers, Inez, Forbes, Alastair 
ORCID: https://orcid.org/0000-0001-7416-9843 and Jones, Kerry S.
(2026)
Alterations of vitamin D metabolism and requirements in clinical conditions with impaired gastro-intestinal and renal function and in critical illness.
The Journal of Steroid Biochemistry and Molecular Biology, 257.
Abstract
Many studies show inverse relationships between the prevalence and severity of clinical conditions and vitamin D status. This may be partly due to reverse causality because of altered organ function, influencing vitamin D metabolism and bioavailability. Here we provide a narrative review of the impact of clinical conditions on vitamin D metabolism reviewing intestinal absorption, vitamin D binding protein (DBP) function and renal metabolism. Dietary vitamin D absorption is dependent on its incorporation in fat droplets in chylomicrons. Gastrointestinal inflammation and impaired fat digestion and absorption lead to decreased vitamin D bioavailability, whereas the hydroxylated form, 25-hydroxyvitamin D (25(OH)D), is less dependent on these factors. Vitamin D metabolites circulate predominantly bound to DBP which facilitates transportation, cellular uptake and regulates hydroxylation into 1,25-dihydroxy vitamin D (1,25(OH)2D) and catabolic products. DBP also plays a key role in scavenging of actin upon cellular damage and inflammation and activation of the innate immune response. A decline in DBP due to actin-scavenging leads to alterations in vitamin D binding, bioavailability and metabolism. The kidney has several roles in vitamin D metabolism: internalisation and hydroxylation of 25(OH)D into 1,25(OH)2D and catabolites and reabsorption of DBP-vitamin D metabolite complex from the glomerular filtrate. Renal damage leads to impairment of these functions. Specific guidance on vitamin D requirements accounting for alterations in vitamin D physiology with many clinical conditions is lacking, except for chronic kidney disease. Understanding how clinical conditions alter organ function and vitamin D metabolism is essential for management of vitamin D status and function.
| Item Type: | Article |
|---|---|
| Additional Information: | Publisher Copyright: © 2025 The Authors |
| Uncontrolled Keywords: | chronic kidney disease,intestinal absorption,vitamin d,vitamin d binding protein,vitamin d requirements,endocrinology,molecular medicine,molecular biology,biochemistry,clinical biochemistry,endocrinology, diabetes and metabolism,cell biology ,/dk/atira/pure/subjectarea/asjc/1300/1310 |
| Faculty \ School: | Faculty of Medicine and Health Sciences > Norwich Medical School |
| UEA Research Groups: | Faculty of Medicine and Health Sciences > Research Groups > Nutrition and Preventive Medicine Faculty of Medicine and Health Sciences > Research Groups > Musculoskeletal Medicine Faculty of Medicine and Health Sciences > Research Centres > Metabolic Health Faculty of Medicine and Health Sciences > Research Centres > Norwich Institute for Healthy Aging Faculty of Medicine and Health Sciences > Research Groups > Gastroenterology and Gut Biology |
| Related URLs: | |
| Depositing User: | LivePure Connector |
| Date Deposited: | 30 Apr 2026 07:50 |
| Last Modified: | 18 Jun 2026 20:50 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/102841 |
| DOI: | 10.1016/j.jsbmb.2025.106909 |
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