Vitamin D Prevents Fractures: Meta-Analysis Evidence
Quick Summary: A large study showed that taking a higher dose of vitamin D (700-800 IU daily) can significantly reduce the risk of bone fractures, especially in older adults. Lower doses didn't have the same effect.
What The Research Found
This research looked at several studies together to see if vitamin D helps prevent broken bones. The results showed that people taking 700-800 IU of vitamin D daily had fewer fractures. This was especially true for hip and other non-spine fractures.
Study Details
- Who was studied: Mostly older adults (average age 70+) and many women.
- How long: The studies followed people for about 2-3 years.
- What they took: Vitamin D supplements, with some also taking calcium. The effective dose was 700-800 IU per day.
What This Means For You
If you're an older adult, especially if you're at risk for falls or have weak bones, taking at least 700-800 IU of vitamin D daily could help prevent fractures. Many multivitamins contain lower doses, so check the label. Talk to your doctor about the right dose for you.
Study Limitations
The study mainly looked at older people, so the results might not be the same for younger adults. Also, some studies used different ways of giving vitamin D, which could affect the results.
Technical Analysis Details
Key Findings
This meta-analysis concluded that oral vitamin D supplementation at doses of 700–800 IU/day significantly reduced nonvertebral and hip fracture risk in older adults. Lower doses (≤400 IU/day) showed no benefit. The fracture risk reduction was dose-dependent, with statistically significant effects only observed at higher daily intakes.
Study Design
The study analyzed 12 randomized controlled trials (RCTs) involving 42,279 participants (median age 70+ years; 70–80% female). Trials compared vitamin D (with or without calcium) against placebo or calcium alone. Median follow-up duration was 2–3 years. Participants were predominantly community-dwelling or institutionalized elderly individuals, many with prior fractures or osteoporosis.
Dosage & Administration
Doses ranged from 300–1,200 IU/day of vitamin D₂ or D₃. Most effective regimens used 700–800 IU/day administered orally, either daily or intermittently (e.g., 100,000 IU every 4 months). Lower doses (≤400 IU/day) were ineffective. Calcium co-supplementation (median 1,000 mg/day) was used in 10 trials but did not alter vitamin D’s dose-dependent efficacy.
Results & Efficacy
At 700–800 IU/day, vitamin D reduced:
- Nonvertebral fractures by 26% (relative risk [RR] 0.74; 95% CI 0.61–0.88; p=0.001).
- Hip fractures by 23% (RR 0.77; 95% CI 0.61–0.97; p=0.02).
Doses ≤400 IU/day showed no significant effect (nonvertebral fracture RR 0.88; 95% CI 0.75–1.03; p=0.11). Heterogeneity was low (I²=0–25%), supporting result reliability.
Limitations
The analysis was limited to elderly populations, reducing generalizability to younger adults. Baseline vitamin D status was inconsistently measured, and intermittent high-dose regimens (e.g., bolus injections) may not reflect daily supplementation efficacy. Calcium co-administration in most trials complicates isolating vitamin D’s independent effects. Future research should clarify optimal dosing in diverse age groups and baseline deficiency states.
Clinical Relevance
For supplement users—particularly adults over 65—this study indicates that ≥700 IU/day of vitamin D is necessary for fracture prevention, while common lower-dose supplements (e.g., 400 IU multivitamins) are ineffective. Combining vitamin D with calcium may enhance bone health, but the dose threshold (700–800 IU/day) is critical. Clinicians should prioritize this dosage range in at-risk populations to reduce fracture incidence.
Original Study Reference
Fracture prevention with vitamin D supplementation: a meta-analysis of randomized controlled trials.
Source: PubMed
Published: 2005-05-11
📄 Read Full Study (PMID: 15886381)
