VDR TaqI and BsmI: Why There's No Genotype-Based Bone Protocol

If you carry the VDR TaqI or BsmI variants and you're looking for the vitamin D dose that matches your genotype, the honest answer is that no such dose exists. The largest and best-designed study of this question — 26,242 people, analysed at the individual level rather than pooled from published summaries — found that FokI, BsmI, ApaI and TaqI are not associated with bone mineral density or with fractures. Your genotype at these positions does not tell you what to take. A measured 25-hydroxyvitamin D level and a bone density scan do.

Key Takeaway

VDR TaqI (rs731236) and BsmI (rs1544410) are two of the most-discussed variants in the consumer genetics world, and there is a large literature attaching them to bone density. That literature does not hold up. The definitive study, the GENOMOS consortium's participant-level meta-analysis, measured bone density by DXA in 26,242 people across nine European research teams and found genotype differences smaller than 0.011 g/cm² — statistically indistinguishable from zero — with fracture odds ratios between 0.98 and 1.02. Smaller meta-analyses built from published summaries do report significant findings, but they contradict each other, including on which allele is supposed to be the bad one. Because of this, no evidence-based vitamin D, calcium or exercise protocol can be keyed to your TaqI or BsmI result. What the evidence does support is unglamorous: meet the established dietary reference intakes, don't exceed the tolerable upper limit on your own, and let measured blood levels and clinical risk factors — not a genotype — drive any decision to do more.

What TaqI and BsmI Are

The vitamin D receptor gene encodes the nuclear receptor that mediates the effects of active vitamin D. TaqI (rs731236) and BsmI (rs1544410) sit near the 3' end of the gene. Neither changes the amino acid sequence of the receptor protein; both were originally identified by the restriction enzymes that cut at their sites, which is why they carry enzyme names rather than being referred to by rsID.

The two are in strong linkage disequilibrium — they tend to be inherited together. A 2004 haplotype meta-analysis by Thakkinstian and colleagues in Osteoporosis International found that the most common VDR haplotype in every ancestry examined was baT, followed by BAt and bAT in Europeans, and bAT and BaT in East Asians (PMID 15057510).

This detail matters more than it looks. Look at which alleles share a chromosome in those haplotypes: baT, BAt, bAT, BaT. Not one of them carries b and t together. A person who is simultaneously "tt" and "bb" would have to carry two copies of a haplotype pairing t with b — and no such haplotype appears among the common ones reported in either Europeans or East Asians. Protocols organised around a combined "TaqI tt plus BsmI bb" genotype are therefore built on a configuration that the linkage data says is uncommon to begin with.

The Study That Settles It

In 2006, the Genetic Markers for Osteoporosis (GENOMOS) consortium published a participant-level meta-analysis in Annals of Internal Medicine (PMID 16908916). Its design is what makes it decisive:

• 26,242 participants (18,405 women) from nine European research teams.
• Prospective and participant-level. Rather than pooling numbers out of published papers, the investigators analysed the raw individual data with a shared protocol — which removes the publication bias and analytic inconsistency that dog conventional meta-analyses of genetic associations.
• Directly measured outcomes. Bone mineral density at the femoral neck and lumbar spine by dual-energy X-ray absorptiometry, plus fracture history. 6,067 participants reported a fracture; 2,088 had vertebral fractures.
• All the usual variants at once: Cdx2, FokI, BsmI, ApaI and TaqI.

The results:

The authors' conclusion is unambiguous: the FokI, BsmI, ApaI and TaqI polymorphisms are not associated with BMD or with fractures.

A null result is often weak evidence, because a small study can fail to find an effect that is really there. That is not the situation here. With confidence intervals as narrow as 0.94 to 1.07, this is a precisely estimated null: the study was large enough to rule out even a small effect. Anything big enough to justify changing your vitamin D dose would have been visible.

Why Other Meta-Analyses Say Otherwise — And Contradict Each Other

Search PubMed and you will find plenty of meta-analyses reporting significant VDR–bone associations. It's worth looking at what they actually say when you line them up, because they do not agree — including on the basic question of which allele is unfavourable.

Read down that column. Four of these analyses point at the B allele as the unfavourable one — either directly (Cooper, Thakkinstian) or by finding bb protective, which is the same claim stated the other way round (Ji, Jia). Two find nothing at all (Uitterlinden, Wang). One reports that heterozygotes do best, which is not an allelic direction at all (Li). One reports two findings that point opposite ways for the same variant within the same paper (Pakpahan). One finds a single modest signal in one genetic model in one region (Al-Barazenji).

Notice what that does to the popular framing. The genotype-based protocols circulating online — including the earlier version of this article — treat "bb" as the risk genotype requiring higher doses. Four of the nine analyses above say the opposite: that bb is the favourable one. The direction of the supposed effect is not settled even among the studies that claim an effect exists.

This is the signature of a literature made of small studies where the significant results get published and the null ones don't. It is exactly the pattern that participant-level analysis was invented to cut through — and when GENOMOS cut through it, the effect disappeared.

Three further cautions about this literature:

• One prominent meta-analysis has been retracted. Zhang et al., "Associations between VDR Gene Polymorphisms and Osteoporosis Risk and Bone Mineral Density in Postmenopausal Women" (Scientific Reports 2018), is frequently cited in support of genotype-specific bone advice. It was retracted in 2021 (retraction notice, PMID 33883680). If you find a source leaning on it, that source has not checked its references.
• Findings often don't survive leaving their population. The 2025 MENA analysis found its one signal only in that region; the 2013 analysis of Asian populations found FokI but not BsmI or ApaI; Ji et al. studied Europeans exclusively. Associations that reverse or vanish across populations are usually artefacts, not ancestry-specific biology.
• Even the positive findings are small, and none of them is a dosing instruction. Where the positive studies report a BMD difference as a percentage, it runs to roughly 2–3% at the hip or spine. More importantly, not one of these papers tested whether changing vitamin D dose by genotype improves any outcome. Association is not a protocol.

What the Genetics of Bone Density Actually Looks Like

Bone density is genuinely heritable — the mistake is thinking that heritability lives in a handful of nameable variants.

The largest genome-wide study to date assessed bone density — estimated by heel quantitative ultrasound — in 426,824 individuals and identified 518 genome-wide significant loci, which together explain about 20% of the variance (Morris et al., Nature Genetics 2019, PMID 30598549). An earlier genome-wide meta-analysis identified 56 BMD loci, of which 14 were also associated with fracture risk, clustering in the RANK–RANKL–OPG, Wnt signalling, mesenchymal stem cell differentiation and endochondral ossification pathways — including LRP5, DKK1, SPTBN1 and MEPE (Estrada et al., Nature Genetics 2012, PMID 22504420).

Two things follow. First, 518 loci accounting for 20% of variance means the average locus contributes a vanishingly small amount — there is no single common variant with enough leverage to key a supplement dose to. Second, the genes these studies actually highlight are not VDR. The bone-density signal in the human genome is real, massively polygenic, and concentrated in different biology than the one consumer reports focus on.

What the Evidence Says About Dosing

Genotype-tiered protocols circulating online — including an earlier version of this page — reach as high as 15,000 IU per day of vitamin D, 2,000 mg of calcium, and 25(OH)D targets of 60–80 ng/mL. None of that is supported by the evidence. Here is what is.

The established intakes

The Institute of Medicine's dietary reference intakes remain the reference standard (Ross et al., J Am Diet Assoc 2011, PMID 21443983; Ross et al., J Clin Endocrinol Metab 2011, PMID 21118827):

The IOM committee also noted that higher 25(OH)D levels were not consistently associated with greater benefit, and that for some outcomes the association was U-shaped, with risk at both low and high levels. The committee's judgement was that vitamin D inadequacy in North America has been overestimated, not underestimated.

Supplementation and fractures

• 81 randomised trials, 53,537 participants. Vitamin D had no effect on total fracture (RR 1.00, 95% CI 0.93–1.07), hip fracture (RR 1.11, 0.97–1.26) or falls (RR 0.97, 0.93–1.02). Bone density differences across all sites ranged from −0.16% to +0.76% over one to five years. Results were the same in trials of high versus low dose and in trials using more than 800 IU/day (Bolland et al., Lancet Diabetes Endocrinol 2018, PMID 30293909).
• VITAL, 25,871 participants, median 5.3 years. 2,000 IU/day of vitamin D3 versus placebo produced no significant effect on total fractures (HR 0.98, 95% CI 0.89–1.08), non-vertebral fractures (HR 0.97) or hip fractures (HR 1.01, 0.70–1.47). Crucially, the effect was not modified by baseline 25(OH)D level (LeBoff et al., N Engl J Med 2022, PMID 35939577).

Both trials enrolled people who were not selected for deficiency, and that limitation is real: vitamin D genuinely matters for people who are actually deficient, and nutritional rickets is a real disease. The point is narrower and firmer — supplementing beyond the reference intake, in people who aren't deficient, doesn't protect bone.

More is not better — and may be worse

This is where the old article's advice was not merely unsupported but pointed the wrong way.

• Higher doses lowered bone density. In a three-year randomised trial, 311 healthy adults aged 55–70 received 400, 4,000 or 10,000 IU/day. Radial volumetric BMD fell by 1.2%, 2.4% and 3.5% respectively — a dose-dependent loss, greatest in the highest-dose group. Tibial BMD was also significantly lower at 10,000 IU/day. There was no gain in bone strength at any dose (Burt et al., JAMA 2019, PMID 31454046).
• A megadose caused harm. In 2,256 women aged 70 and over, a single annual 500,000 IU dose increased falls (incidence rate ratio 1.15, 95% CI 1.02–1.30) and fractures (IRR 1.26, 95% CI 1.00–1.59) compared with placebo (Sanders et al., JAMA 2010, PMID 20460620).

A daily intake of 15,000 IU sits well above the tolerable upper intake level, which was set on the basis of hypercalcaemia risk. There is no genotype that makes it appropriate, and no study has ever tested it as a genotype-matched strategy.

What a current guideline says

The Endocrine Society's 2024 clinical practice guideline (Demay et al., J Clin Endocrinol Metab 2024, PMID 38828931) suggests:

• Against empiric vitamin D supplementation above the dietary reference intake to lower disease risk in healthy adults under 75.
• Against routine 25(OH)D screening in the general population — including in people with obesity or dark skin complexion — in the absence of an established indication, because no trial evidence supports it and no optimal target level has been established for disease prevention.
• For daily rather than intermittent high-dose administration in people over 50 for whom vitamin D is indicated.

Note the tension with popular advice: the guideline does not tell healthy adults to chase a high 25(OH)D number, and does not recommend testing everybody. Whether you have an indication to test or treat is a clinical question, and that is genuinely a conversation for a provider rather than a decision to make from a raw data file.

So What Should You Actually Do?

If bone health is your concern, the useful moves are not genetic:

1. Measure the thing itself, if it's indicated. Bone density is directly measurable by DXA — it's what every study above used as the outcome. A measured value beats an inference from genotype, and the inference has been shown not to work.
2. Ask about testing rather than assuming. If you have risk factors — prior fracture, long-term glucocorticoids, malabsorption, early menopause, low body weight, a family history of hip fracture — those are what drive assessment, and they're worth raising with a clinician. A TaqI or BsmI result is not.
3. Meet the reference intake, don't chase a number above it. 600 IU/day up to age 70, 800 IU/day after, with calcium from food where possible.
4. Stay under the upper limit unless a clinician has a reason. 4,000 IU/day is the ceiling of the IOM's tolerable range for a reason, and the trial evidence above shows the downside is real rather than theoretical.
5. Load the skeleton. Weight-bearing and resistance exercise remains standard advice for bone health. It is not genotype-dependent, and nothing in the VDR literature justifies prescribing a different training volume by genotype.

FAQ

How do I find my VDR TaqI and BsmI genotype? Search your 23andMe or AncestryDNA raw data for rs731236 (TaqI) and rs1544410 (BsmI) — the rsIDs, not the enzyme names. Whether either is present depends on which chip version generated your file. Finding them is easy; the problem is that the result doesn't support a decision.

I already know I'm "tt" or "bb". Does that mean I'm at risk? No. In the 26,242-participant analysis, fracture odds ratios for all VDR alleles fell between 0.98 and 1.02 — that is, indistinguishable from average risk. Separately, none of the commonly reported VDR haplotypes carries b and t on the same chromosome, so a combined "tt plus bb" genotype is not a common configuration in the first place.

Then why do so many articles give genotype-specific vitamin D doses? Because a large literature of small studies reports significant associations, and it is easy to summarise those without noticing that they contradict each other, that one influential one was retracted, or that the definitive participant-level study found nothing. No study has ever tested genotype-matched dosing against standard dosing for any bone outcome.

Should I target 60–80 ng/mL of 25(OH)D? There is no evidence base for that target. The IOM found that 20 ng/mL or more meets the requirement of at least 97.5% of the population, that higher levels were not consistently associated with greater benefit, and that some outcomes showed U-shaped risk. The 2024 Endocrine Society guideline explicitly declined to define an optimal target for disease prevention.

Is 5,000–10,000 IU daily safe long-term? It is above the tolerable upper intake level, and it has been directly tested. Over three years, 10,000 IU/day produced 3.5% loss of radial bone density versus 1.2% on 400 IU/day, with no gain in bone strength. That is a reason not to self-prescribe it, whatever your genotype.

Does VDR genotype at least affect how much my blood level rises per dose? No trial has demonstrated a genotype-dependent dose–response that would change what you should take. And the underlying premise is weak: in VITAL, the fracture effect of supplementation was not modified even by baseline 25(OH)D level — an actual measurement of vitamin D status, which is far more informative than a receptor genotype.

Is any VDR variant associated with anything bone-related? The one borderline signal in the definitive study was the Cdx2 promoter variant, associated with a 9% reduction in vertebral fracture risk (95% CI, 0% to 18%; P = 0.039). Note that the confidence interval touches zero and the direction is protective. It is not TaqI, not BsmI, and it is not a basis for taking anything.

Is genetic testing useless for bone health, then? For these particular variants, yes. Bone density is strongly genetic overall — but it's spread across hundreds of loci that together explain about 20% of variance, in different pathways than VDR. That is a real scientific finding and a poor consumer product: no small panel of variants can currently tell you what to take.

Educational Content Disclaimer

This article provides educational information about genetic variants and is not intended as medical advice. It does not diagnose any condition. Decisions about vitamin D testing, supplementation, bone density screening or treatment should be made with a qualified healthcare provider who can weigh your medical history and risk factors. Do not start, stop or change supplementation on the basis of a raw genetic data file.