Vitamin D in the blood encounters many restrictions in getting to the cells
Clinical Significance of Analysis of Vitamin D Status in Various Diseases
Nutrients 2020, 12(9), 2788; https://doi.org/10.3390/nu12092788
by Magdalena Kowalówka 1OrcID,Anna K. Główka 1OrcID,Marta Karaźniewicz-Łada 2,* and Grzegorz Kosewski 1
1 Department of Bromatology, Poznan University of Medical Sciences, 42 Marcelińska Street, 60-354 Poznań, Poland
2 Department of Physical Pharmacy and Pharmacokinetics, Poznan University of Medical Sciences, 6 Święcickiego Street, 60-781 Poznań, Poland

VitaminDWiki suspects about half of the people with Vitamin D deficient diseases
have enough Vitamin D in their blood, but not in their cells
For many it is more important to increase vitamin D and D getting to cells than to get a Vitamin D test
Genes - some of which can be improved by supplements
CYP27B1 category listing contains the following
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Cancers might alter CYP24A1 gene
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Vitamin D Binding Protein category listing has items and the following introduction
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Vitamin D Binding Protein has a list of health problems
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Vitamin D Receptor
Vitamin D Receptor is associated in over 58 autoimmune studies
A poor Vitamin D Receptor is associated with many cancers (oral cancer in this case) – Jan 2019
studies have found 50 Cancers associated with poor Vitamin D Receptor
- Some studies found that a Cancer has "learned" how to deactivate the Vitamin D receptor
The activation of the Vitamin D receptor decreases with age 6 studies as of Sept 2020
Additional information on the Genes in VitaminDWiki
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Cofactors (in addition to Vitamin D Receptor supplements)
Vitamin D Cofactors in a nutshell table show the importance of each
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📄 Download the PDF from VitaminDWiki
Vitamin D plays a role not only in the proper functioning of the skeletal system and the calcium-phosphate equilibrium, but also in the immune system, the cardiovascular system and the growth and division of cells. Although numerous studies have reported on the analysis of vitamin D status in various groups of patients, the clinical significance of measurements of vitamin D forms and metabolites remains ambiguous. This article reviews the reports analyzing the status of vitamin D in various chronic states. Particular attention is given to factors affecting measurement of vitamin D forms and metabolites. Relevant papers published during recent years were identified by an extensive PubMed search using appropriate keywords. Measurement of vitamin D status proved to be a useful tool in diagnosis and progression of metabolic syndrome, neurological disorders and cancer. High performance liquid chromatography coupled with tandem mass spectrometry has become the preferred method for analyzing the various forms and metabolites of vitamin D in biological fluids. Factors influencing vitamin D concentration, including socio-demographic and biochemical factors as well as the genetic polymorphism of the vitamin D receptor, along with vitamin D transporters and enzymes participating in vitamin D metabolism should be considered as potential confounders of the interpretation of plasma total 25(OH)D concentrations.