Vitamin A
Vitamin ·Exploratory record · not publication-reviewed ·Updated July 13, 2026
Essential for vision, immune function, skin health, and cell differentiation. Available as preformed retinol or provitamin A (beta-carotene).
Exploratory record, not a reviewed medical publication.
See the editorial and medical-review policies for the publication gate.
This generated database record has not completed a claim-level review by a qualified human medical reviewer. Bibliography links and evidence labels are not approval. The page remains available for reference and is excluded from search indexing.
What the research says.
A quick, data-only summary. The full evidence, dosing, and sources are below.
Vitamin A is a vitamin most often used for vision health, immune function, skin health. NutriStack rates the overall evidence as strong. A typical adult dose is Preformed retinol: 2,500–10,000 IU (10,000 IU is UL). Beta-carotene: no UL but contraindicated in smokers., commonly taken as retinyl palmitate or beta-carotene (safer at high doses). This profile indexes 19 sources.
The bottom line
Evidence rating strong. Most-documented uses: vision health, immune function, skin health. 19 sources indexed (1995–2024), with 0 interaction records on file.
How it works, mechanistically.
Core mechanism
Retinol is converted to retinal (essential for rhodopsin in rod cells for night vision) and retinoic acid (binds RAR/RXR nuclear receptors regulating gene expression for cell differentiation, immune function, and skin turnover).18,14
Dosing & protocol.
What it actually costs.
Real-world pricing across three quality tiers. Assumes Retinyl Palmitate / Mixed Carotenoids.
Assumes 2,500-5,000 IU/day. Vendor basis: NOW/iHerb, Vitacost, Life Extension, and Amazon marketplace; mixed carotenoid formulas price higher than retinyl palmitate. Updated 2026-05-28.
The same dose, as food.
How much you'd eat to match a supplemental dose.
Preformed retinol and beta-carotene are not interchangeable for everyone.
Carotenoid conversion is less efficient in some people.
Full safety detail.
Side effects
- Toxicity at high doses (hypervitaminosis A)
- Headache
- Nausea
- Birth defects (high-dose retinol in pregnancy)
- Beta-carotene: increased lung cancer risk in smokers (28-46% increase in landmark ATBC and CARET trials)
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Meta-analyses & systematic reviews
13- 1The Relationship of Vitamin A and Neonatal Respiratory Diseases: A Meta-AnalysisPMIDLi Y, Zhang R, Li Z et al. · The clinical respiratory journal · 2024
Li Y, Zhang R, Li Z et al.. The Relationship of Vitamin A and Neonatal Respiratory Diseases: A Meta-Analysis. The clinical respiratory journal. 2024
- 2Effects of primary or secondary prevention with vitamin A supplementation on clinically important outcomes: a systematic review of randomised clinical trials with meta-analysis and trial sequential analysisSource linkedPMIDBjelakovic G, Nikolova D, Gluud C et al. · BMJ Open · 2024
- 3The Association between Malaria and β-Carotene Levels: A Systematic Review and Meta-AnalysisPMIDKotepui KU, Mahittikorn A, Wilairatana P et al. · Antioxidants (Basel, Switzerland) · 2023
Kotepui KU, Mahittikorn A, Wilairatana P et al.. The Association between Malaria and β-Carotene Levels: A Systematic Review and Meta-Analysis. Antioxidants (Basel, Switzerland). 2023
- 4The Effect of Beta-Carotene on Cognitive Function: A Systematic ReviewPMIDAbrego-Guandique DM, Bonet ML, Caroleo MC et al. · Brain sciences · 2023
Abrego-Guandique DM, Bonet ML, Caroleo MC et al.. The Effect of Beta-Carotene on Cognitive Function: A Systematic Review. Brain sciences. 2023
- 5Vitamin a supplementation during pregnancy in shaping child growth outcomes: A meta-analysisPMIDMa G, Chen Y, Liu X et al. · Critical reviews in food science and nutrition · 2023
Ma G, Chen Y, Liu X et al.. Vitamin a supplementation during pregnancy in shaping child growth outcomes: A meta-analysis. Critical reviews in food science and nutrition. 2023
- 6Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of agePMIDImdad A, Mayo-Wilson E, Haykal MR et al. · The Cochrane database of systematic reviews · 2022
12% reduction in all-cause mortality in children aged 6-59 months
- 7Influence of Vitamin A supplementation on inflammatory biomarkers in adults: a systematic review and meta-analysis of randomized clinical trialsSource linkedPMIDMohammadi H, Talebi S, Ghavami A et al. · Sci Rep · 2022
- 8Metabolism of Neonatal Vitamin A Supplementation: A Systematic ReviewPMIDGannon BM, Rogers LM, Tanumihardjo SA · Advances in nutrition (Bethesda, Md.) · 2021
Gannon BM, Rogers LM, Tanumihardjo SA. Metabolism of Neonatal Vitamin A Supplementation: A Systematic Review. Advances in nutrition (Bethesda, Md.). 2021
- 9Vitamin A and Bone Fractures: Systematic Review and Meta-AnalysisPMIDKnapik JJ, Hoedebecke SS · Journal of special operations medicine : a peer reviewed journal for SOF medical professionals · 2021
Knapik JJ, Hoedebecke SS. Vitamin A and Bone Fractures: Systematic Review and Meta-Analysis. Journal of special operations medicine : a peer reviewed journal for SOF medical professionals. 2021
- 10Preformed vitamin A and risk of type 2 diabetes: a systematic review and meta-analysisSource linkedPMIDChen G, Lu F, Xu L et al. · Nutrients · 2021
- 11Efect of vitamin A suplementation: a systematic reviewPMIDSoares MM, Silva MA, Garcia PPC et al. · Ciencia & saude coletiva · 2019
Soares MM, Silva MA, Garcia PPC et al.. Efect of vitamin A suplementation: a systematic review. Ciencia & saude coletiva. 2019
- 12Vitamin A and Breast Cancer Survival: A Systematic Review and Meta-analysisPMIDHe J, Gu Y, Zhang S · Clinical breast cancer · 2018
He J, Gu Y, Zhang S. Vitamin A and Breast Cancer Survival: A Systematic Review and Meta-analysis. Clinical breast cancer. 2018
- 13Effects of vitamin A supplementation on immune function with concurrent vaccines in children: a systematic review and meta-analysisSource linkedPMIDVillamor E, Fawzi WW · Lancet Infect Dis · 2005
Randomized controlled trials
2- 14Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular diseasePMIDOmenn GS et al. · N Engl J Med · 1996
CARET trial stopped early: 28% more lung cancers and 17% more deaths in the beta-carotene + retinol group vs placebo among smokers and asbestos workers
- 15Alpha-Tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliancePMIDATBC Study Group · J Natl Cancer Inst · 1996
Beta-carotene supplementation was associated with increased lung cancer risk (RR 1.16; 95% CI 1.02-1.33) in male smokers
Reviews & position papers
3- 16Vitamin A ToxicityPMIDBastos Maia S et al. · StatPearls · 2023
Excessive preformed vitamin A causes acute and chronic toxicity (hypervitaminosis A); acute toxicity can occur at doses >=500,000 IU; 10,000 IU/day upper limit
- 17Role of Vitamin A in the Immune SystemPMIDHuang Z et al. · J Clin Med · 2018
Vitamin A is known as an anti-inflammation vitamin; critical role in enhancing immune function, involved in development of immune system, regulates cellular and humoral immune responses
- 18Vitamin A and VisionPMIDZhong M et al. · Subcell Biochem · 2016
In all visual systems, 11-cis-retinal complexed with opsin serves as the chromophore; retinal is essential for the visual cycle in rod and cone cells
Observational studies
1- 19Teratogenicity of high vitamin A intakePMIDRothman KJ et al. · N Engl J Med · 1995
Among women who took >10,000 IU/day of preformed vitamin A, estimated prevalence of birth defects was 1 per 57; threshold near 10,000 IU/day of supplemental vitamin A
Common questions.
Quick answers about Vitamin A, drawn from the data on this page.
What is Vitamin A?
Essential for vision, immune function, skin health, and cell differentiation. Available as preformed retinol or provitamin A (beta-carotene).
What is Vitamin A used for?
Commonly cited benefits of Vitamin A include: Vision health; Immune function; Skin health; Cell growth; Reproductive health. NutriStack rates the overall evidence as strong.
What is a typical dose of Vitamin A?
A typical adult dose of Vitamin A is Preformed retinol: 2,500–10,000 IU (10,000 IU is UL). Beta-carotene: no UL but contraindicated in smokers.. The commonly recommended form is Retinyl palmitate or beta-carotene (safer at high doses). These are general ranges, not personalized advice; confirm the right dose with a clinician.
What are the side effects of Vitamin A?
Reported side effects include toxicity at high doses (hypervitaminosis a), headache, nausea, birth defects (high-dose retinol in pregnancy), beta-carotene: increased lung cancer risk in smokers (28-46% increase in landmark atbc and caret trials). This is educational information; check with a healthcare professional before use.
How strong is the evidence for Vitamin A?
NutriStack rates this as Strong, meaning multiple high-quality meta-analyses or systematic reviews converge on the same finding. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.
Use this with your stack
Vitamin A in NutriStack.
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