NutriStack
Vitamin D3 supports immune function and reduces respiratory infection risk, the receipts.
A large individual-participant meta-analysis (Martineau 2017, BMJ) found a real protective effect, with the largest benefit in those with low baseline 25-OH-D.
Strong evidence, per the methodology. Strongest 4 studies linked to PubMed.
Recommendation, contrary evidence, and dose are all on this page.
The studies
Strongest evidence, sourced.
Sorted by study tier (meta-analyses first, then RCTs, then reviews) and recency. Every entry links to PubMed by PMID.
At a glance
- Substances
- Vitamin D3
- Evidence tier
- Strong evidence
- Strongest studies surfaced
- 4 of 4 matching
- One-line verdict
- One of the most defensible vitamin D claims.
- Last verified
- May 30, 2026
Top 4 studies
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Review
Immunologic Effects of Vitamin D on Human Health and Disease PMID 32679784
Vitamin D exerts immunomodulatory activities on innate and adaptive immune systems; low 25-OHD associated with increased risk of autoimmune diseases and infections
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Meta-analysis
Effect of Vitamin D3 Supplementation on Severe COVID-19: A Meta-Analysis of Randomized Clinical Trials PMID 38794642
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Meta-analysis
Vitamin D3 and COVID-19 Outcomes: An Umbrella Review of Systematic Reviews and Meta-Analyses PMID 36829806
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Meta-analysis
Vitamin D supplementation reduced the risk of acute respiratory tract infection (OR 0.88); greatest benefit in those with baseline 25-OHD <25 nmol/L and with daily/weekly dosing
Contrary evidence
What pushes back.
Caveats, null findings, and methodological limits that hold the tier where it is.
What argues against the claim
- Bolus dosing (one large monthly dose) does not work.
- Benefit is largest in deficient individuals; effect shrinks in already-replete cohorts.
Recommendation
What the evidence supports.
What we recommend, with caveats
1,000 to 4,000 IU daily, taken with a fat-containing meal. Aim for a serum 25-OH-D of 30 to 50 ng/mL. Test before going above 5,000 IU/day.
Tier criteria are documented at /methodology/evidence-tiers. Sourcing standards at /methodology/interactions.
Stack interaction risks
Where these substances clash.
Documented pairings involving the substances behind this claim. Cautions and conflicts come first.
Pairs in the database
- Chlorthalidone + Vitamin D3 · Caution
- Digoxin + Vitamin D3 · Caution
- Hydrochlorothiazide + Vitamin D3 · Caution
- Vitamin A + Vitamin D3 · Caution
- Alendronate + Vitamin D3 · Synergy
- Amlodipine + Vitamin D3 · Synergy
Open the free interaction checker at /interactions to scan a full routine.
Goal hubs
Where this claim feeds in.
Goal-based hubs that index this claim alongside related supplements and protocols.
Related goal hubs
Before you go
One claim, opened up. NutriStack does this for every claim in the database.
The full library lives at /research. Every entry follows the same shape: the verdict, the studies, the contrary evidence, the recommendation, and the primary literature.