Vitamin D3
Research reviewed: Up until 03/2026
Vitamin D3 (Cholecalciferol (Vitamin D3)) is a dietary supplement with 6 published peer-reviewed studies involving 2,840 participants, researched for Bone Mineral Density & Fracture Prevention, Immune System Support, Bone Strength (High-Dose Assessment) and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Bone Mineral Density & Fracture Prevention
StrongImmune System Support
ModerateBone Strength (High-Dose Assessment)
ModerateCardiovascular & Metabolic Health
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Bone Mineral Density & Fracture Prevention
To determine the effect of supplemental vitamin D3 plus calcium on bone mineral density in adults over 65.
Study Type
Randomised, double-blind, controlled
Purpose
To determine the effect of supplemental vitamin D3 plus calcium on bone mineral density in adults over 65.
Dose
700 IU vitamin D3/day + 500 mg calcium
Participants
389 adults aged ≥65
Duration
3 years
Results
Calcium and vitamin D3 supplementation significantly reduced total-body bone loss and non-vertebral fracture risk. BMD at the femoral neck and spine was maintained vs placebo.
How They Measured It
DXA (BMD at hip, spine, femoral neck, radius), non-vertebral fracture incidence
To evaluate the effect of 4-monthly oral vitamin D3 supplementation on fractures and mortality in community-dwelling adults.
Study Type
Randomised, double-blind, controlled
Purpose
To evaluate the effect of 4-monthly oral vitamin D3 supplementation on fractures and mortality in community-dwelling adults.
Dose
100,000 IU oral vitamin D3 every 4 months
Participants
2,686 community-dwelling men and women aged ≥65
Duration
5 years
Results
Vitamin D3 supplementation significantly reduced fracture risk by 22% vs placebo. Serum 25(OH)D levels were maintained in the supplemented group throughout the 5-year trial.
How They Measured It
Fracture incidence (all types), mortality, serum 25(OH)D
To evaluate the effect of supplemental vitamin D3 on bone mineral density.
Study Type
Systematic review and meta-analysis
Purpose
To evaluate the effect of supplemental vitamin D3 on bone mineral density.
Dose
Various
Participants
Meta-analysis across multiple RCTs
Duration
Various
Results
Vitamin D3 supplementation significantly improved BMD, particularly at the lumbar spine and total body. Effects were larger in individuals with baseline vitamin D deficiency. Combination with calcium produced greater benefits.
How They Measured It
Meta-analysis of BMD data from eligible RCTs
Immune System Support
To review the efficacy, safety, and public health implications of cholecalciferol supplementation.
Study Type
Comprehensive review
Purpose
To review the efficacy, safety, and public health implications of cholecalciferol supplementation.
Dose
Various (400-50,000 IU/day)
Participants
Review
Duration
Various
Results
High-dose vitamin D3 demonstrated benefits including improved immune homeostasis, glycaemic control, and reduced inflammation in specific populations. Benefits most pronounced in individuals with baseline deficiency (<20 ng/mL serum 25(OH)D).
How They Measured It
Review of RCTs across immune, bone, metabolic, and cardiovascular outcomes
Bone Strength (High-Dose Assessment)
To evaluate the effect of high-dose vitamin D3 supplementation on volumetric bone density and bone strength.
Study Type
Randomised clinical trial
Purpose
To evaluate the effect of high-dose vitamin D3 supplementation on volumetric bone density and bone strength.
Dose
400 IU/day (n=109), 4,000 IU/day (n=100), or 10,000 IU/day (n=102)
Participants
311 healthy adults aged 55-70
Duration
3 years
Results
Higher vitamin D3 doses (4,000 and 10,000 IU/day) were associated with lower total volumetric BMD and greater bone loss at the radius vs 400 IU/day. Results suggest supra-physiological doses do not improve bone strength and may be harmful. Optimal supplementation ~400-2,000 IU/day.
How They Measured It
High-resolution peripheral quantitative CT (HR-pQCT), DXA, bone strength parameters
Cardiovascular & Metabolic Health
To review cholecalciferol (vitamin D3) as the preferred supplemental form for raising serum 25(OH)D.
Study Type
Narrative and systematic review
Purpose
To review cholecalciferol (vitamin D3) as the preferred supplemental form for raising serum 25(OH)D.
Dose
Various
Participants
Review
Duration
Various
Results
Vitamin D3 (cholecalciferol) is the preferred form over D2 for raising serum 25(OH)D. Benefits include bone health, reduced infection risk, immune modulation, and potentially cardiovascular protection. Optimal serum levels are 40-60 ng/mL.
How They Measured It
Comparative review of vitamin D2 vs D3, serum 25(OH)D efficacy, multiple clinical outcome reviews
Frequently Asked Questions
Common questions about Vitamin D3 research
There are currently 11 peer-reviewed studies on Vitamin D3 (Cholecalciferol (Vitamin D3)), involving 2,840 total participants. Research covers Bone mineral density & fracture prevention, Immune system support, Muscle function and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (6 human studies), and reported outcomes.
Vitamin D3 has been researched for: Bone mineral density & fracture prevention, Immune system support, Muscle function, Cardiovascular & metabolic health. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 6 out of 11 studies are human trials. Human trials carry more weight in our evidence scoring system.
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