Question explored with the scientific record
Conversation so far
- 1 Recommended dosage Vitamin D supplement for elderly for bone health
- 2 What is 800 IU in micrograms?
- 3 How about Vitamin D + Vitamin K
Answered on this page ↓
How about Vitamin D + Vitamin K
The short version: vitamin D alone does not prevent fractures in healthy older adults; the benefit appears only when calcium is added, and the evidence for vitamin K is absent from this retrieval.
The retrieval here is thin on the exact question. It covers vitamin D dosing and fracture outcomes in older adults, but it contains no studies of vitamin K at all. That absence is a fact about the search, not proof that vitamin K does nothing. The mechanism is plausible: vitamin K helps proteins that bind calcium into bone, but no record here tests it.
What the records do show is that vitamin D alone is weak. A Cochrane review of about 28,000 people found vitamin D alone did not reduce hip fractures, with a risk ratio of 1.12 [5]. Another meta-analysis of about 9,000 people found the same, a risk ratio of 1.1 [6]. But vitamin D plus calcium did reduce hip fractures: risk ratio 0.84 in about 50,000 people [5], and 0.82 in about 46,000 people [6]. The pattern is consistent across reviews [3][4].
The dose matters. A 2021 systematic review recommends 1,000–2,000 IU daily to keep blood levels above 30 ng/mL [1]. That is 25–50 micrograms. But high-dose boluses are not harmless: one trial of 500,000 IU once a year in 2,317 elderly women found more falls and fractures, not fewer [2].
| Group | Hip fracture risk ratio | People studied |
|---|---|---|
| Vitamin D alone | 1.12 [5] | ~28,000 |
| Vitamin D alone | 1.1 [6] | ~9,000 |
| Vitamin D + calcium | 0.84 [5] | ~50,000 |
| Vitamin D + calcium | 0.82 [6] | ~46,000 |
The evidence is observational for the vitamin K half, and the trials that exist were not retrieved here. What is proven: if you supplement, use daily doses of 1,000–2,000 IU with calcium, not annual megadoses [1][2]. Whether adding vitamin K helps is not answered by these records.
My call: vitamin D alone is not worth it for fracture prevention; vitamin D with calcium is, and vitamin K is unproven here. Confidence: moderate.
Sources used 6
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Major Approaches to the Dosage of Vitamin D in the Elderly: A Systematic Review
A systematic review of vitamin D dosing in the elderly finds that maintaining serum 25(OH)D above 30 ng/mL with 1,000-2,000 IU daily reduces falls, fractures, and may improve COVID-19 outcomes.
DOI: 10.34256/mdnt2131 -
Role of vitamin D in acquired immune and autoimmune diseases
This narrative review concludes that observational data associate low vitamin D with immune and autoimmune diseases but that inconsistent RCTs and design caveats mean long-term, large, double-blind placebo-controlled trials are still needed to confirm causal effects of supplemen…
DOI: 10.3109/10408363.2014.901291 -
Vitamin D supplementation –Is it the time to stop wasting money on vitamin D?
An editorial synthesizing recent meta-analyses and major randomized trials, arguing that vitamin D supplementation alone provides little or no benefit for fracture prevention, falls, or cancer/cardiovascular disease outcomes in the general population, with marginal or uncertain …
DOI: 10.33883/jms.v22i1.442 -
Vitamin D and vitamin D analogues for preventing fractures associated with involutional and post-menopausal osteoporosis
This systematic review evaluates the efficacy of vitamin D and its analogues in preventing fractures in older adults, concluding that vitamin D alone is unlikely to prevent fractures, while vitamin D combined with calcium may reduce hip fractures in institutionalized older adult…
DOI: 10.1002/14651858.CD000227.pub2 -
Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men
This systematic review evaluates the effectiveness of vitamin D and its analogues in preventing fractures among post-menopausal women and older men, concluding that while vitamin D alone is unlikely to prevent fractures, its combination with calcium may reduce the risk of hip an…
DOI: 10.1002/14651858.CD000227.pub4 -
Need for Additional Calcium to Reduce the Risk of Hip Fracture with Vitamin D Supplementation: Evidence from a Comparative Metaanalysis of Randomized Controlled Trials
This study extends previous meta-analyses by demonstrating that vitamin D supplementation reduces the risk of hip fractures in elderly individuals only when combined with additional calcium supplementation.
DOI: 10.1210/jc.2006-1404