Do vitamin D supplements prevent fractures?

For most healthy adults, no. Three large randomised trials and a pooled analysis of 81 trials all point the same way, and the pooled result is close enough to zero that the statisticians can rule out even a five per cent reduction. For two specific groups the answer is different, and that is what the rest of this page is about.

Established. Vitamin D deficiency causes real bone disease. Rickets in children and osteomalacia in adults are not in dispute, and preventing them is the reason vitamin D matters at all. The question on this page is narrower: whether taking a supplement when you are not deficient prevents the fractures that ordinary people actually get.

The question that decides your answer

Almost every argument about vitamin D happens because two different questions are being answered at once.

The first is whether correcting a deficiency helps bone. It does. The second is whether adding a supplement to a body that already has enough helps bone. That is the one the big trials tested, and the answer there is close to a flat no.

So before reading any number below, work out which side of that line you are on. Adequate is usually taken as a blood level of at least 50 nmol/L (20 ng/mL), and deficiency as below 30 nmol/L (12 ng/mL). If nobody has measured yours, the honest position is that you do not know.

What the three biggest trials found

These are not small studies with surrogate outcomes. They counted broken bones in tens of thousands of people over five years.

VITAL is the one worth sitting with. It was designed to find an effect, it ran for over five years, it had nearly 2,000 fractures to count, and it looked specifically for subgroups where the supplement might work. It found none. The authors checked age, sex, race, body mass index and starting blood level of vitamin D, and the answer did not change in any of them.

What happens when you add up every trial ever done

Single trials can be unlucky. So a group in New Zealand and Scotland pooled 81 randomised trials covering 53,537 people and asked the question again.

Total fractures came out at a relative risk of 1.00, with a confidence interval from 0.93 to 1.07. Falls came out at 0.97 (0.93 to 1.02). Bone density moved between minus 0.16 per cent and plus 0.76 per cent over one to five years, which is a rounding error in a bone.

The interesting part is what they did next. They ran a trial sequential analysis, which is the statistical way of asking whether more research could still change the answer. For fractures and falls the estimate sat inside the futility boundary for reductions of 15 per cent, 10 per cent and 7.5 per cent, and for total fractures also 5 per cent. In plain terms: we now have enough evidence to say that vitamin D on its own does not cut fractures even by small amounts, and running more trials of the same kind would not be a good use of anyone's money.

The Cochrane review, working from 53 trials and 91,791 participants, reached the same place and rated its own certainty as high. Vitamin D alone did not prevent hip fracture (RR 1.12, 0.98 to 1.29) or any new fracture (RR 1.03, 0.96 to 1.11).

Myth. The claim that vitamin D builds stronger bones in healthy adults is the one this evidence retires. It does not raise bone density to any degree a person would notice, and it does not reduce the fractures that bone density is supposed to predict.

Where supplements genuinely work

Now the other half, and it is the half that usually gets left out of headlines in both directions.

The same Cochrane review found that vitamin D taken together with calcium does reduce hip fractures, with a relative risk of 0.84 (0.74 to 0.96). That is a real result, rated high quality. The question is what it means for a given person, and the answer depends entirely on how likely that person was to break a hip in the first place.

For someone living at home, this is one hip fracture prevented for every thousand people who take the supplement for a year, and the confidence interval reaches down to zero. For someone living in a care home, it is nine per thousand per year. Same pills, same relative risk, an outcome nine times more worthwhile in the second group.

The trial that shows this most clearly is also the oldest. In 1992, 3,270 French women with an average age of 84, living in care homes and low in vitamin D, took 800 IU of vitamin D3 with 1.2 g of calcium daily. Hip fractures fell by 43 per cent and all non-vertebral fractures by 32 per cent. Those women were deficient, frail and indoors. They are not the same people as the VITAL participants, and the results should not be swapped between them.

Not for everyone. If you are over 80, live in residential care, rarely go outside, or have had a fracture already, the evidence on this page does not say your supplement is pointless. It says the opposite. This is the group where vitamin D with calcium has the best case in all of nutrition.

More is not better, and past a point it is worse

The instinct when a supplement does not work is to take more of it. Three trials tested that directly, and all three found harm rather than benefit.

Over three years, healthy adults aged 55 to 70 who took 4,000 IU a day ended up with bone density at the wrist 3.9 mg HA/cm³ lower than those on 400 IU, and those on 10,000 IU ended up 7.5 mg lower. The dose-response ran the wrong way. In 200 older people who had already fallen, monthly doses of 60,000 IU produced falls in 66.9 per cent of them against 47.9 per cent on 24,000 IU. And 2,256 Australian women given a single 500,000 IU dose once a year had more falls (rate ratio 1.15, 1.02 to 1.30) and more fractures (1.26, 1.00 to 1.59) than women on placebo, with the excess concentrated in the three months right after each dose.

Unsettled. The picture on large intermittent doses is not clean, and we are not going to pretend it is. D-Health gave 60,000 IU monthly to 20,326 people and found no sign of harm at all, and its authors said so plainly. The trials that found harm were smaller, and two of them used much larger or differently timed doses. What can be said is that no trial has found large doses to be better, and several have found them worse.

Pooling those trials rather than reading them one at a time gives the same answer in fewer words. Large occasional doses prevent neither falls nor fractures, and on falls the pooled estimate leans towards more of them rather than fewer. The spacing of the dose is doing something the total amount does not capture.

Sorting the trials by daily dose is where the shape of this becomes obvious. Between 800 and 1,000 IU a day, vitamin D lowered fractures and falls. Above 1,000 IU a day it did nothing. A sensible dose-response curve rises with the dose. This one rises, flattens, and in the intermittent trials turns over.

The clearest single demonstration comes from broken wrists, where the outcome is the bone itself rather than a count of events. Given after a wrist fracture, the equivalent of 1,800 IU a day left the healing bone measurably weaker. The equivalent of 700 IU changed nothing in either direction. The larger dose was the worse one, in the one setting where everybody expects vitamin D to help.

The falls result has a twist worth seeing

Falls are half of the fracture story, and the way they respond does not match the explanation everyone reaches for.

Unsettled. Active vitamin D analogues, which are prescription forms rather than the capsules on a shop shelf, cut falls in older people by about a fifth. The same trials measured grip strength, back extensor strength and overall muscle strength, and none of the three changed. So the falls did fall, and muscle strength is not the route by which it happened. That leaves the mechanism unexplained, and it is a good reason to be careful about carrying a result from a prescription analogue across to a bottle of ordinary vitamin D.

Where the expert bodies stand

The US Preventive Services Task Force recommends against daily supplementation with 400 IU or less of vitamin D and 1,000 mg or less of calcium for preventing fractures in postmenopausal women living at home. That is a grade D, which in their language means do not do this. For men, for premenopausal women and for higher doses they say the evidence is insufficient. That statement is from 2018 and the task force lists the topic as being updated, so it may change.

The Endocrine Society, in its 2024 guideline, suggests against routine supplementation beyond the reference intake for healthy people aged 50 to 74, and against routinely measuring vitamin D in the blood of healthy adults. Both are conditional recommendations rather than strong ones.

There is one comparison on the task force's own pages that says more than any of the numbers above. For preventing falls in people over 65, exercise carries a grade B recommendation, which means do it. Vitamin D was pulled out of that 2024 falls update entirely and sent to a separate review that is still unfinished. One of those two interventions has the evidence behind it, and it is not the one sold in a bottle.

So what should you actually do

If you eat oily fish a couple of times a week and spend some time outdoors, this page does not ask anything of you. Very few foods contain vitamin D naturally, and fortified milk carries about 3 micrograms a cup, so most people get a modest amount and that is normal.

If you think you might be low

Get the blood test rather than guessing. Ask for it directly if you have a BMI of 30 or more, have had gastric bypass surgery, keep your skin covered, or have a condition that stops you absorbing fat. Those groups run low reliably, whatever they eat.

If you take orlistat or a statin

Orlistat reduces absorption of vitamin D from food and supplements, so levels fall rather than rise. Statins cut cholesterol production, and the body builds vitamin D from cholesterol, so they may reduce how much it makes. Neither is a reason to stop a medicine, and both are a reason to measure rather than assume.

If you already take a supplement

The reference intake is 15 micrograms (600 IU) a day up to age 70 and 20 micrograms (800 IU) after that, and the upper limit is 100 micrograms (4,000 IU). Signs of toxicity are unlikely below 250 micrograms (10,000 IU) a day, so an ordinary supplement is not dangerous. It is simply unlikely to do what you are buying it for, unless you were short to begin with.

That ceiling is an adult ceiling, which is easy to miss when one bottle serves a household. In Europe the limit is set by age: 100 micrograms a day for adults and adolescents, and half that, 50 micrograms, for children aged one to ten.

For a sense of what any of these doses does to the thing the trials measured, fortified food gives the cleanest exchange rate anyone has pooled. Across 34 publications in 2,398 adults and 1,532 children, an average of 16 micrograms a day raised blood levels by 21 nmol/L, with a larger rise in people who started below 50 nmol/L and a curve that flattens near 21 micrograms a day. D3 moved the level more than D2 did. That is the size of the lever. Every trial on this page pulled it and counted the fractures anyway.

If your goal is actually fewer broken bones

Then the evidence points at exercise, at not falling, and at treating osteoporosis when it is diagnosed. Vitamin D is a small part of a bigger answer, and for most people it is the part that has already been taken care of.

What would change this answer

We are not neutral about being wrong, so here is what we are watching.

• The US Preventive Services Task Force review is unfinished. A draft posted in December 2024 proposed recommending against vitamin D for both fractures and falls, and a draft is not a recommendation. When the final version appears, this page changes.
• Almost every large trial enrolled people who were not deficient. A trial that recruits only people below 30 nmol/L would answer a question none of these trials answered, and the Chapuy result suggests it might answer it differently.
• The hip fracture estimate for vitamin D alone still has a wide interval and sits slightly above one. The pooled analysis says plainly that uncertainty remains about whether it might increase hip fractures. That is an open question, not a settled harm.

How we searched

Sources

1. vitd-b01 · Randomised controlled trial(s) · randomised controlled trial · n = 25,871
   Supplemental vitamin D₃, as compared with placebo, did not have a significant effect on total fractures (which occurred in 769 of 12,927 participants in the vitamin D group and in 782 of 12,944 participants in the placebo group; hazard ratio, 0.98; 95% confidence interval [CI], 0.89 to 1.08; P = 0.70), nonvertebral fractures (hazard ratio, 0.97; 95% CI, 0.87 to 1.07; P = 0.50), or hip fractures (hazard ratio, 1.01; 95% CI, 0.70 to 1.47; P = 0.96).
   
   Who: men 50+ and women 55+ in the United States, not recruited on the basis of vitamin D deficiency, low bone mass or osteoporosis
   Effect: total fractures hazard ratio 0.98 (95% CI 0.89 to 1.08); nonvertebral 0.97 (0.87 to 1.07); hip 1.01 (0.70 to 1.47)
   Certainty: single large trial, pre-specified primary end points
   LeBoff et al., New England Journal of Medicine, 2022 · checked 2026-09-16 · we read the abstract
2. vitd-b02 · Randomised controlled trial(s) · randomised controlled trial (fractures were a tertiary outcome) · n = 20,326 analysed
   Over a median follow-up of 5·1 years (IQR 5·1-5·1), 568 (5·6%) participants in the vitamin D group and 603 (5·9%) in the placebo group had one or more fractures. There was no effect on fracture risk overall (HR 0·94 [95% CI 0·84-1·06]), and the interaction between randomisation group and time was not significant (p=0·14).
   
   Who: adults aged 60 to 84 living in Australia, mean age 69.3 years, 45.7% women
   Effect: total fractures hazard ratio 0.94 (95% CI 0.84 to 1.06); non-vertebral 0.96 (0.85 to 1.08); major osteoporotic 1.00 (0.85 to 1.18); hip 1.11 (0.86 to 1.45)
   Certainty: tertiary outcome of a large trial; authors call for more research
   Waterhouse et al., The Lancet Diabetes & Endocrinology, 2023 · checked 2026-09-16 · we read the abstract
3. vitd-b03 · Randomised controlled trial(s) · randomised controlled trial · n = 20,326 analysed
   These findings do not support concerns that bolus doses of vitamin D administered monthly increase fracture risk.
   
   Who: adults aged 60 to 84 living in Australia
   Effect: no increase in fracture risk with monthly 60,000 IU dosing
   Certainty: authors' own interpretation of a tertiary outcome
   Waterhouse et al., The Lancet Diabetes & Endocrinology, 2023 · checked 2026-09-16 · we read the abstract
4. vitd-b04 · Meta-analysis or systematic review · systematic review, meta-analysis and trial sequential analysis of randomised trials · n = 53,537 across 81 trials
   In pooled analyses, vitamin D had no effect on total fracture (36 trials; n=44 790, relative risk 1·00, 95% CI 0·93-1·07), hip fracture (20 trials; n=36 655, 1·11, 0·97-1·26), or falls (37 trials; n=34 144, 0·97, 0·93-1·02). Results were similar in randomised controlled trials of high-dose versus low-dose vitamin D and in subgroup analyses of randomised controlled trials using doses greater than 800 IU per day. In pooled analyses, there were no clinically relevant between-group differences in bone mineral density at any site (range -0·16% to 0·76% over 1-5 years).
   
   Who: adults over 18, all settings; trials of hydroxylated analogues excluded
   Effect: total fracture relative risk 1.00 (95% CI 0.93 to 1.07, 36 trials, n=44,790); hip fracture 1.11 (0.97 to 1.26, 20 trials, n=36,655); falls 0.97 (0.93 to 1.02, 37 trials, n=34,144); bone density change between groups −0.16% to 0.76% over 1 to 5 years
   Certainty: trial sequential analysis placed the estimate inside the futility boundary for reductions of 15%, 10%, 7.5% and 5%
   Bolland, Grey and Avenell, The Lancet Diabetes & Endocrinology, 2018 · checked 2026-09-16 · we read the abstract
5. vitd-b05 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis, GRADE assessed · n = 91,791 across 53 trials
   There is high quality evidence that vitamin D alone, in the formats and doses tested, is unlikely to be effective in preventing hip fracture (11 trials, 27,693 participants; risk ratio (RR) 1.12, 95% confidence intervals (CI) 0.98 to 1.29) or any new fracture (15 trials, 28,271 participants; RR 1.03, 95% CI 0.96 to 1.11).
   
   Who: post-menopausal women and older men in community, nursing home and hospital settings
   Effect: vitamin D alone: hip fracture relative risk 1.12 (95% CI 0.98 to 1.29, 11 trials, n=27,693); any new fracture 1.03 (0.96 to 1.11, 15 trials, n=28,271)
   Certainty: high quality evidence (GRADE)
   Avenell et al., Cochrane Database of Systematic Reviews, 2014 · checked 2026-09-16 · we read the abstract
6. vitd-b06 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis, GRADE assessed · n = 49,853 across nine trials
   There is high quality evidence that vitamin D plus calcium results in a small reduction in hip fracture risk (nine trials, 49,853 participants; RR 0.84, 95% confidence interval (CI) 0.74 to 0.96; P value 0.01). In low-risk populations (residents in the community: with an estimated eight hip fractures per 1000 per year), this equates to one fewer hip fracture per 1000 older adults per year (95% CI 0 to 2). In high risk populations (residents in institutions: with an estimated 54 hip fractures per 1000 per year), this equates to nine fewer hip fractures per 1000 older adults per year (95% CI 2 to 14).
   
   Who: post-menopausal women and older men; community residents versus institution residents
   Effect: hip fracture relative risk 0.84 (95% CI 0.74 to 0.96); absolute effect one fewer hip fracture per 1,000 per year in the community (95% CI 0 to 2) and nine fewer per 1,000 per year in institutions (95% CI 2 to 14)
   Certainty: high quality evidence (GRADE)
   Avenell et al., Cochrane Database of Systematic Reviews, 2014 · checked 2026-09-16 · we read the abstract
7. vitd-b07 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis · n = up to 71,032 participants depending on the outcome
   Hypercalcaemia, which was usually mild (2.6 to 2.8 mmol/L), was more common in people receiving vitamin D or an analogue, with or without calcium (21 trials, 17,124 participants, RR 2.28, 95% CI 1.57 to 3.31)... There was also a small increased risk of gastrointestinal symptoms (15 trials, 47,761 participants, RR 1.04, 95% CI 1.00 to 1.08)... and a significant increase in renal disease (11 trials, 46,548 participants, RR 1.16, 95% CI 1.02 to 1.33).
   
   Who: post-menopausal women and older men in trials of vitamin D with or without calcium
   Effect: renal disease relative risk 1.16 (95% CI 1.02 to 1.33, 11 trials, n=46,548); hypercalcaemia 2.28 (1.57 to 3.31, 21 trials, n=17,124); gastrointestinal symptoms 1.04 (1.00 to 1.08); mortality 0.97 (0.93 to 1.01)
   Certainty: not separately graded in the abstract
   Avenell et al., Cochrane Database of Systematic Reviews, 2014 · checked 2026-09-16 · we read the abstract
8. vitd-b08 · Randomised controlled trial(s) · randomised controlled trial · n = 3,270
   Among the women who completed the 18-month study, the number of hip fractures was 43 percent lower (P = 0.043) and the total number of nonvertebral fractures was 32 percent lower (P = 0.015) among the women treated with vitamin D3 and calcium than among those who received placebo.
   
   Who: healthy ambulatory women in nursing homes and apartment houses for the elderly in France, mean age 84 (SD 6), with low vitamin D status and raised parathyroid hormone
   Effect: hip fractures 43% lower (P = 0.043); all non-vertebral fractures 32% lower (P = 0.015); no confidence intervals reported in the abstract
   Certainty: single trial from 1992, reported without confidence intervals
   Chapuy et al., New England Journal of Medicine, 1992 · checked 2026-09-16 · we read the abstract
9. vitd-b09 · Randomised controlled trial(s) · randomised controlled trial · n = 36,282
   Intention-to-treat analysis indicated that participants receiving calcium plus vitamin D supplementation had a hazard ratio of 0.88 for hip fracture (95 percent confidence interval, 0.72 to 1.08), 0.90 for clinical spine fracture (0.74 to 1.10), and 0.96 for total fractures (0.91 to 1.02). The risk of renal calculi increased with calcium plus vitamin D (hazard ratio, 1.17; 95 percent confidence interval, 1.02 to 1.34). Censoring data from women when they ceased to adhere to the study medication reduced the hazard ratio for hip fracture to 0.71 (95 percent confidence interval, 0.52 to 0.97).
   
   Who: postmenopausal women aged 50 to 79 in the Women's Health Initiative
   Effect: hip fracture hazard ratio 0.88 (95% CI 0.72 to 1.08); total fractures 0.96 (0.91 to 1.02); kidney stones 1.17 (1.02 to 1.34); hip fracture 0.71 (0.52 to 0.97) when data are censored at the point women stopped taking the tablets
   Certainty: single large trial; the adherence analysis is secondary
   Jackson et al., New England Journal of Medicine, 2006 · checked 2026-09-16 · we read the abstract
10. vitd-b10 · Randomised controlled trial(s) · randomised controlled trial, three doses · n = 311 randomised, 287 completed
    At trial end, radial volumetric BMD was lower for the 4000 IU group (-3.9 mg HA/cm3 [95% CI, -6.5 to -1.3]) and 10 000 IU group (-7.5 mg HA/cm3 [95% CI, -10.1 to -5.0]) compared with the 400 IU group with mean percent change in volumetric BMD of -1.2% (400 IU group), -2.4% (4000 IU group), and -3.5% (10 000 IU group).
    
    Who: 311 community-dwelling healthy adults aged 55 to 70 in Calgary, Canada, with baseline 25(OH)D of 30 to 125 nmol/L
    Effect: radial bone density versus the 400 IU group: −3.9 mg HA/cm³ (95% CI −6.5 to −1.3) at 4,000 IU and −7.5 mg HA/cm³ (−10.1 to −5.0) at 10,000 IU; no significant difference in bone strength
    Certainty: single trial; authors say further research is needed to know whether it is harmful
    Burt et al., JAMA, 2019 · checked 2026-09-16 · we read the abstract
11. vitd-b11 · Randomised controlled trial(s) · randomised controlled trial, three arms · n = 200
    Although higher monthly doses of vitamin D were effective in reaching a threshold of at least 30 ng/mL of 25-hydroxyvitamin D, they had no benefit on lower extremity function and were associated with increased risk of falls compared with 24,000 IU.
    
    Who: community-dwelling men and women aged 70 and older in Zurich with a previous fall; mean age 78; 58% vitamin D deficient at baseline
    Effect: falls over 12 months: 66.9% (95% CI 54.4 to 77.5) on 60,000 IU monthly against 47.9% (35.8 to 60.3) on 24,000 IU monthly (P = .048)
    Certainty: falls were a secondary end point in a small trial
    Bischoff-Ferrari et al., JAMA Internal Medicine, 2016 · checked 2026-09-16 · we read the abstract
12. vitd-b12 · Randomised controlled trial(s) · randomised controlled trial · n = 2,256
    Women in the cholecalciferol (vitamin D) group had 171 fractures vs 135 in the placebo group; 837 women in the vitamin D group fell 2892 times (rate, 83.4 per 100 person-years) while 769 women in the placebo group fell 2512 times (rate, 72.7 per 100 person-years; incidence rate ratio [RR], 1.15; 95% confidence interval [CI], 1.02-1.30; P = .03). The incidence RR for fracture in the vitamin D group was 1.26 (95% CI, 1.00-1.59; P = .047) vs the placebo group (rates per 100 person-years, 4.9 vitamin D vs 3.9 placebo).
    
    Who: community-dwelling women aged 70 and older at high risk of fracture in Australia; median baseline 25(OH)D 49 nmol/L
    Effect: falls incidence rate ratio 1.15 (95% CI 1.02 to 1.30); fractures 1.26 (1.00 to 1.59); the excess of falls was concentrated in the three months after each dose
    Certainty: single trial; the timing analysis was post hoc
    Sanders et al., JAMA, 2010 · checked 2026-09-16 · we read the abstract
13. vitd-b13 · Position of an expert body · expert body recommendation · n = evidence synthesis
    The USPSTF recommends against daily supplementation with 400 IU or less of vitamin D and 1000 mg or less of calcium for the primary prevention of fractures in community-dwelling, postmenopausal women.
    
    Who: community-dwelling adults without osteoporosis, vitamin D deficiency or a previous fracture
    Effect: grade D for postmenopausal women at these doses; grade I (insufficient evidence) for men, premenopausal women, and for higher doses
    Certainty: USPSTF grade D; the topic is listed as being updated, and the 2018 statement remains the published one
    U.S. Preventive Services Task Force, final recommendation statement, 2018 · checked 2026-09-16 · we read the full text
14. vitd-b14 · Position of an expert body · expert body recommendation · n = evidence synthesis
    The current recommendation does not address the use of vitamin D to prevent falls; this evidence will be reviewed in a separate USPSTF recommendation (in progress).
    
    Who: community-dwelling adults 65 and older at increased risk of falls
    Effect: exercise interventions grade B; multifactorial interventions grade C; vitamin D not addressed
    Certainty: USPSTF grades B and C
    U.S. Preventive Services Task Force, falls prevention in community-dwelling older adults, 2024 · checked 2026-09-16 · we read the full text
15. vitd-b15 · Position of an expert body · clinical practice guideline, GRADE based · n = evidence synthesis
    In the general population aged 50 to 74 years, we suggest against routine vitamin D supplementation beyond the recommended Dietary Reference Intake for this population. (2 | ⊕⊕⊕◯)
    
    Who: general population by age band
    Effect: conditional recommendation against routine supplementation for ages 50 to 74 (moderate certainty); conditional recommendation against routine 25(OH)D screening in healthy adults (very low certainty)
    Certainty: both are conditional recommendations, marked 2 in GRADE terms
    Demay et al., Endocrine Society clinical practice guideline, Journal of Clinical Endocrinology & Metabolism, 2024 · checked 2026-09-16 · we read the abstract
16. vitd-04 · Position of an expert body
    ≥50 nmol/L or ≥20 ng/mL are generally considered adequate for bone and overall health in healthy individuals
    
    Who: healthy individuals
    Effect: ≥50 nmol/L adequate, <30 nmol/L deficient
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
17. vitd-05 · Position of an expert body
    In children, vitamin D deficiency is manifested as rickets, a disease characterized by a failure of bone tissue to become properly mineralized, resulting in soft bones and skeletal deformities.
    
    Who: children
    Effect: rickets
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
18. vitd-06 · Position of an expert body
    In adults and adolescents, vitamin D deficiency can lead to osteomalacia, in which existing bone is incompletely or defectively mineralized during the remodeling process, resulting in weak bones.
    
    Who: adults and adolescents
    Effect: osteomalacia
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
19. vitd-13 · Position of an expert body
    Individuals with a body mass index (BMI) of 30 or more have lower serum 25(OH)D levels
    
    Who: adults with obesity or bypass surgery
    Effect: lower serum 25(OH)D
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
20. vitd-14 · Position of an expert body
    Few foods naturally contain vitamin D. The flesh of fatty fish (such as trout, salmon, tuna, and mackerel) and fish liver oils are among the best sources.
    
    Who: general
    Effect: limited natural food sources
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
21. vitd-16 · Position of an expert body
    Fortified foods provide most of the vitamin D in American diets. For example, almost all of the U.S. milk supply is voluntarily fortified with about 3 mcg/cup (120 IU), usually in the form of vitamin D3.
    
    Who: US population
    Effect: fortification is the main dietary source
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
22. vitd-02 · Position of an expert body
    Adults 19-50 years: 15 mcg (600 IU); Adults >70 years: 20 mcg (800 IU)
    
    Who: adults
    Effect: 600 IU to age 70, 800 IU from 71
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
23. vitd-03 · Position of an expert body
    Tolerable Upper Intake Level (adults 19-70 and >70): 100 mcg (4,000 IU)
    
    Who: adults 19+
    Effect: UL 4,000 IU/day
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
24. vitd-12 · Position of an expert body
    Signs and symptoms of toxicity are unlikely at daily intakes below 250 mcg (10,000 IU)
    
    Who: adults
    Effect: toxicity unlikely <10,000 IU/day
    NIH Office of Dietary Supplements, Health Professional Fact Sheet: Vitamin D · checked 2026-09-15
25. vitd-17 · Position of an expert body
    The weight-loss drug orlistat (Xenical and alli), together with a reduced-fat diet, can reduce the absorption of vitamin D from food and supplements, leading to lower 25(OH)D levels.
    
    Who: people taking orlistat with a reduced-fat diet
    Effect: lower 25(OH)D levels
    NIH Office of Dietary Supplements, Vitamin D - Health Professional Fact Sheet · checked 2026-09-16 · we read the full text
26. vitd-18 · Position of an expert body
    Statin medications reduce cholesterol synthesis. Because endogenous vitamin D is derived from cholesterol, statins may also reduce vitamin D synthesis.
    
    Who: people taking statins
    Effect: possible reduction in vitamin D synthesis
    NIH Office of Dietary Supplements, Vitamin D - Health Professional Fact Sheet · checked 2026-09-16 · we read the full text
27. vitd-x1 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised controlled trials of intermittent or single high-dose vitamin D supplementation · n = 15 randomised trials out of 527 screened articles
    In a meta-analysis of RCTs, intermittent or single high-dose vitamin D supplementation showed no significant beneficial effect in the prevention of either falls (RR, 1.03 [95% CI, 0.98-1.09]; I2 = 56.6%; n = 11) or fractures (RR, 0.99 [95% CI, 0.87-1.14]; I2 = 48.3%; n = 11)...In contrast, intermittent or single high-dose vitamin D3 supplementation increased the risk of falls on the borderline of statistical significance (RR, 1.06 [95% CI 0.99-1.15]; P = 0.051; I2 = 50.0%; n = 7).
    
    Who: adults in 15 randomised trials, 11 contributing to the falls analysis and 11 to the fracture analysis
    Effect: falls relative risk 1.03 (95% CI 0.98 to 1.09) and fractures 0.99 (95% CI 0.87 to 1.14); for vitamin D3 specifically, falls 1.06 (95% CI 0.99 to 1.15, p = 0.051)
    Certainty: the increase in falls is borderline rather than established; the apparent fracture benefit in trials under 1,000 participants (RR 0.74, 95% CI 0.57 to 0.96) vanished in larger trials (RR 1.06, 95% CI 0.92 to 1.21), which is the classic signature of small-study bias
    Osteoporosis International, 2023 · checked 2026-09-17 · we read the abstract
28. vitd-x2 · Meta-analysis or systematic review · meta-analysis of randomised controlled trials stratified by daily dose and by dosing interval, excluding ergocalciferol, calcitriol, trials with 10 or fewer events and follow-up under six months · n = 32 studies
    Vitamin D supplementation with daily dose of 800 to 1,000 mg was associated with lower risks of osteoporotic fracture and fall (pooled relative risk [RR], 0.87; 95% confidence interval [CI], 0.78 to 0.97 and RR, 0.91; 95% CI, 0.85 to 0.98), while studies with <800 or >1,000 mg/day did not.
    
    Who: adults in 32 randomised trials reporting fractures or falls
    Effect: at 800 to 1,000 units a day, osteoporotic fracture relative risk 0.87 (95% CI 0.78 to 0.97) and falls 0.91 (95% CI 0.85 to 0.98); studies below 800 or above 1,000 a day showed neither
    Certainty: subgroup comparison across trials, not a randomised dose comparison, so the band is suggestive; note that the results section of the abstract prints the unit as 'mg' where the conclusion of the same paper says 'IU' — the quote is reproduced exactly as published, and 800 to 1,000 IU is what is meant
    Endocrinology and Metabolism (Seoul), 2022 · checked 2026-09-17 · we read the abstract
29. vitd-x3 · Randomised controlled trial(s) · randomised controlled trial with a six-week bolus dose in two intervention groups and an unsupplemented control group, with high-resolution peripheral quantitative CT of the fractured radius at four visits over twelve weeks · n = 32 participants, 10 on low dose, 11 on high dose and 11 controls
    Compared with the control group, high-dose vitamin D3 supplementation resulted in a decreased trabecular number (regression coefficient β: -0.22; p < 0.01) and lower compression stiffness (B: -3.63; p < 0.05, together with an increase in the bone resorption marker CTX (B: 0.062; p < 0.05). No statistically significant differences were observed between the control and low-dose intervention group.
    
    Who: people with a distal radius fracture in a Western postmenopausal population; a third had baseline 25(OH)D below 50 nmol/L and 70 per cent below 75 nmol/L
    Effect: against control, the high dose gave a lower trabecular number (regression coefficient -0.22, p < 0.01), lower compression stiffness (-3.63, p < 0.05) and higher bone resorption marker CTX (0.062, p < 0.05); the low dose differed from control on nothing
    Certainty: a very small trial, 32 people in three arms, with imaging and biochemical outcomes rather than clinical ones; it cannot establish harm on its own, but it points the same way as the trials in which 4,000 and 10,000 IU a day lowered bone density
    Journal of Bone and Mineral Research, 2021 · checked 2026-09-17 · we read the abstract
30. vitd-c05 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised controlled trials of calcitriol, alfacalcidol and eldecalcitol · n = 771 participants in the three fall trials and 2,431 in the ten muscle-strength trials
    The results showed that in the pooled analysis of three active vitamin D analogues, active vitamin D analogues reduced the risk of fall by 19%. Due to a lack of sufficient data, no separate subgroup analysis was conducted on the effect of each active vitamin D analogue on falls. In the pooled and separate analysis of active vitamin D analogues, no significant effects were found on global muscle, hand grip, and back extensor strength.
    
    Who: elderly people at risk of falls
    Effect: risk of fall reduced by 19% in the pooled analysis of three analogues; no significant effect on global muscle, hand grip or back extensor strength, with only quadriceps strength improving
    Certainty: these are prescription analogues of vitamin D, not ordinary cholecalciferol supplements; few trials per analogue, and no separate subgroup analysis of falls was possible
    Xiong et al., Frontiers in Endocrinology, 2024 · checked 2026-09-17 · we read the abstract
31. vitd-e2-06 · Meta-analysis or systematic review · systematic review and meta-analysis of randomised controlled trials of at least 4 weeks with a placebo food control, quality scored on the Jadad scale · n = 3 930 across 34 publications
    Random-effects meta-analysis of all studies combined (mean dose 16.2 μg/d) indicated a pooled treatment effect of 21.2 nmol/L (95% CI: 16.2, 26.2), with a greater effect for studies using cholecalciferol than ergocalciferol.
    
    Who: 2 398 adults and 1 532 children across 34 publications, all free of illness affecting vitamin D absorption
    Effect: pooled effect 21.2 nmol/L (95% CI 16.2 to 26.2), larger below a baseline 25(OH)D of 50 nmol/L and at doses of 10 mcg a day or more, with a nonlinear dose response that flattened near 21 mcg a day
    Certainty: heterogeneity was high, above 75 per cent, so the pooled number describes a spread of trials rather than a reliable single answer. A calcium dose 500 mg higher in the intervention arm made the effect smaller
    Dunlop et al., The Journal of Nutrition, 2021 · checked 2026-09-18 · we read the abstract
32. vitd-e2-09 · Position of an expert body
    the UL for children aged 1-10 has been increased from 25µg a day to 50µg a day
    
    Who: European Union population by age group
    Effect: tolerable upper intake level raised in 2012 from 50 to 100 mcg a day for adults and adolescents, and from 25 to 50 mcg a day for children aged 1 to 10
    Certainty: an upper level is the amount unlikely to cause harm over a lifetime, not a target and not a dose anybody needs to reach. These are the values EFSA re-affirmed in its 2023 review, which also set separate levels of 25 mcg for infants under 6 months and 35 mcg for 7 to 11 months
    Upper intake levels reviewed for vitamin D and calcium, European Food Safety Authority, 2012 · checked 2026-09-18 · we read the full text