- GeneVDR, the vitamin D receptor
- Variants testedrs2228570 (FokI), rs1544410 (BsmI), rs7975232 (ApaI), rs2107301
- What it controlsHow strongly your cells respond to the vitamin D you have
- If reducedA higher blood level is needed for the same biological effect
- What changesVitamin D3 dose informed by genotype, paired with K2 and magnesium
What the gene does
The vitamin D receptor is a transcription factor. Vitamin D binds it, and the receptor then switches on a large set of genes involved in bone, immune function and calcium handling. Without a responsive receptor, circulating vitamin D has nowhere to act.
This is why a blood level alone is an incomplete picture. Two people can carry the same serum 25-hydroxyvitamin D and get different amounts of biological work out of it.
What the variants change
FokI is the one that alters the protein directly. It shifts the start codon, producing a receptor three amino acids longer that is measurably less active in transcription assays. BsmI, ApaI and the regulatory site at rs2107301 sit outside the coding region and are thought to act through messenger RNA stability and linkage with nearby functional sites, which is why their effects vary more between populations.
A systematic review of 77 studies found vitamin D pathway variants associated with muscle mass and function rather than with circulating level alone. A separate meta-analysis pooled 26 studies on BsmI and bone density.
What it means for you
Reduced receptor response doesn't mean vitamin D stops working for you. It means the level needed to produce a given amount of activity is higher than average. The practical consequence is a starting dose informed by genotype rather than a population default, then confirmed against an actual blood test.
Two companions matter here. Vitamin K2 activates the proteins that direct absorbed calcium into bone rather than soft tissue, and that matters more at higher vitamin D doses. Magnesium is the cofactor for the enzymes that hydroxylate vitamin D into its active form, so low magnesium quietly limits how much of a dose becomes usable.
What your formula does
Where the genotype predicts reduced receptor response, your formula starts vitamin D3 above the population default and pairs it with K2 and magnesium. Your report shows the genotype behind the number, so you can see the reasoning rather than just the dose.
The full literature review. VDR variation and the vitamin D dose response, covering all four sites in the panel and fourteen published studies. Read it (14 references)
Find out which version you carry
One saliva test reads all four VDR sites alongside 53 other nutritional markers.
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