Supplement

Vitamin D3

Also known as Cholecalciferol

Fat-soluble vitamin synthesised in skin from UVB exposure and activated by the liver and kidneys; regulates calcium and phosphate absorption for bone health and modulates immune and mood pathways via vitamin D receptors.

4linked conditions

39linked studies

On this pageEvidence Availability Outcomes & conditions →

Evidence

What the research actually shows

We link to relevant studies and leave interpretation to you and your healthcare professional.

Evidence analytics

Where the evidence is concentrated

Number of audited published findings for Vitamin D3 by condition. Drill into a pair page for the full breakdown.

Putative uses

Where people report using it and what trials suggest

Strong evidenceCorrection of deficiency / rickets & osteomalacia prevention
Moderate evidenceBone health in older adults (with calcium, fracture risk)
Moderate evidenceImmune support / respiratory infections in deficient people

Where the evidence is negative

Common claims the trials do not support

Large trials (VITAL, ~26k participants) found no reduction in cardiovascular events or cancer in people who were not deficient.
No overall mortality benefit from routine high-dose supplementation in the general population.
Does not improve depression symptoms in adequately nourished people (meta-analyses null or marginal).

Fat-soluble vitamin essential for calcium absorption and bone health. Correction of deficiency is well established; most other proposed benefits have not survived large trials.

Safety notes: Megadoses risk hypercalcaemia. Most adults should stay within guideline upper limits unless a deficiency is confirmed by testing.

Evidence grades reflect study quality and consistency, not marketing claims.

39studies referenced

32journals

2014–2026publication range

01Vitamin D supplementation and incidence of major depressive disorder - A randomized clinical trialAhl NM, et al. · Clinical nutrition (Edinburgh, Scotland) · 2026PMID 41506003 ↗02Effects of personalized vitamin D(3) on inflammation in colorectal cancer patients: a randomized trialGwenzi T, et al. · British journal of cancer · 2026PMID 41507560 ↗03Role of vitamin D as adjuvant therapy on multiple sclerosis: an updated systematic review and meta-analysis of randomized controlled trialsSerag I, et al. · European journal of medical research · 2025PMID 40797337 ↗04The effects of Omega-3 fatty acids and vitamin D supplementation on the quality of life and blood inflammation markers in newly diagnosed breast cancer women: An open-labelled randomised controlled trialAlmassri HF, et al. · Clinical nutrition ESPEN · 2025PMID 39577691 ↗05The effect of vitamin D supplementation on mental and functional health outcomes in African Americans with type 2 diabetesJones KE, et al. · The Journal of steroid biochemistry and molecular biology · 2025PMID 39952368 ↗06

Search PubMed ↗Find clinical trials ↗

What trials found, in numbers

Summaries of published trial results for this compound, grouped by condition. Numbers are reported exactly as the researchers published them — we never calculate or convert.

How to read this table

Benefit: What the trial saw happen: whether the measured outcome moved in the helpful direction in that one study (the tag on each row: “Benefit seen”, “No clear benefit” or “Unclear”). It is a study result — not advice, and not a promise it will work for you.
Evidence: How strong the research behind that result is. A meta-analysis pools many studies (strongest); a systematic review collates them; an RCT tests against a control (placebo); observational studies only watch — they can suggest, not prove.
Effect size: How large the measured change was, exactly as the researchers published it. “No number reported” means the abstract gave no effect size — we never invent one.

In short: benefit is what was observed; evidence is how much you should trust the observation. A “Benefit seen” tag on a weak study counts for far less than the same tag on a meta-analysis.

Bone Health (3 outcomes)

Outcome measured	What trials found	Effect size	People studied	Duration	Type of evidence	Study
hip fractures	Vitamin D3 did not significantly lower hip fracture risk vs placebo in 25,871 adults over a median of 5.3 years. (hazard ratio, 1.01; 95% CI, 0.70 to 1.47; P=0.96)No clear benefit	no number reported	25,871	median follow-up of 5.3 years	RCT · 2022	PMID 35939577
nonvertebral fractures	Vitamin D3 did not significantly lower nonvertebral fracture risk vs placebo in 25,871 adults over a median of 5.3 years. (hazard ratio, 0.97; 95% CI, 0.87 to 1.07; P=0.50)No clear benefit	no number reported	25,871	median follow-up of 5.3 years	RCT · 2022

Outcomes & conditions

Why people look into Vitamin D3 — and what they report

Associated conditions and community-reported outcomes, wrapped together on one page. Aggregates appear only once enough reports arrive.

Outcomes & conditions →

Important: This page reflects observational, aggregate-only community reporting and independent published research. It is not medical advice, and it does not claim any compound treats, cures, or is effective for any condition. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or treatment.

Availability

Where to get Vitamin D3 (UK)

How this compound is sold in the UK, and where our readers typically find it.

Retailer search links — we may earn commission on purchases at no cost to you. Commission never affects our evidence ratings.

Search Vitamin D3 on Amazon UK →Search Vitamin D3 on Holland & Barrett →Search Vitamin D3 on iHerb →

Outcome measured	What trials found	Effect size	People studied	Duration	Type of evidence	Study
depression improvement and quality of life	Cognitive behavioral therapy improved depression and quality of life more than undefined psychotherapy or placebo.Benefit seen	no number reported	—	—	Systematic review · 2021	PMID 35369008
depression severity	Long-term, high-dose vitamin D3 was ineffective for reducing depression severity compared to no treatment.No clear benefit	no number reported	—	long-term	Systematic review · 2021	PMID 35369008
depression severity	Acupressure reduced depression severity more effectively than usual care or sham acupressure.Benefit seen	no number reported	—	—	Systematic review · 2021	PMID 35369008
Change in mood scores (PHQ-8)	Vitamin D3 showed no significant difference in mood score changes vs placebo in 18 353 adults over a median of 5.3 years. (mean difference for change in mood scores, 0.01 points [95% CI, -0.04 to 0.05 points])No clear benefit	no number reported	18 353	median treatment duration was 5.3 years	RCT · 2020	PMID 32749491
Risk of depression or clinically relevant depressive symptoms	Vitamin D3 showed no significant difference in depression risk vs placebo in 18 353 adults over a median of 5.3 years. (hazard ratio, 0.97 [95% CI, 0.87 to 1.09]; P = .62)No clear benefit	no number reported	18 353	median treatment duration was 5.3 years	RCT · 2020	PMID 32749491

Outcome measured	What trials found	Effect size	People studied	Duration	Type of evidence	Study
amelioration of fatigue	Fatigue amelioration occurred in 72% vs 50% placebo in 120 people over 4 weeks. (P=0.01; odds ratio [OR] 2.63, 95% CI for OR 1.23-5.62)Benefit seen	72%	120	4 weeks	RCT · 2016	PMID 28033244
intra-individual change in the fatigue assessment scale (FAS)	Fatigue scores improved by 3.3 points vs placebo in 120 people over 4 weeks. (95% confidence interval [CI] for change -14.1 to 4.1; P=0.01)Benefit seen	-3.3	120	4 weeks	RCT · 2016	PMID 28033244