Vitamin A

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Vitamin A is a group of fat-soluble retinoids, including retinol, retinal, and retinoic acid. It is essential for maintaining clear vision, particularly in low-light conditions, as it is a critical component of rhodopsin, the light-absorbing molecule in the retina. Beyond vision, it supports the immune system by aiding the production and activity of white blood cells. This nutrient is also fundamental to cell growth and differentiation, which is necessary for the development and maintenance of tissues such as the skin, hair, and internal organs. It contributes to reproductive health in both men and women and is required for proper embryonic development. Certain forms, such as carotenoids, act as antioxidants to help protect cells from free radical damage. Given its diverse roles, maintaining adequate intake is important for overall wellness, influencing everything from the integrity of epithelial tissues to bone health.

Natural sources
CarrotsSweet potatoesSpinachKaleLiverEggsDairy products (milk, cheese)Cod liver oilMangoesApricotsCantaloupe

Ingredient forms

No public comparison lists found.

Timing & Intake
AnytimeWith foodTake with a meal containing dietary fat
As a fat-soluble nutrient, Vitamin A is best absorbed when consumed with a meal containing some dietary fat.
Daily Intake
RDA (Men)3000 IU
RDA (Women)2333 IU
RDI3000 IU
Optimal Dosage
Minimum2500 IU
Maximum5000 IU
Safety & Toxicity
Upper Limit (UL)10000 IU
Toxicity Threshold25000 IU
Toxicity Effectliver damage, headache
3 safety notes
  • Pregnant women should exercise caution with Vitamin A supplementation, as excessive intake (especially preformed Vitamin A) can be teratogenic (cause birth defects).
  • Individuals with liver disease should avoid high doses of Vitamin A.
  • Long-term excessive intake can lead to hypervitaminosis A, characterized by symptoms like liver damage, bone density changes, and central nervous system issues.
Goals
Gut Health
Gut Health
Impact
Highest effect
Typical dose:750–3000 mcg

Vitamin A is critical for the differentiation of epithelial cells lining the gut and for the production of Secretory IgA (sIgA), the primary antibody that protects mucosal surfaces from pathogens. Deficiency impairs gut barrier function.

Focuses on
Gut LiningRegularityGut Inflammation
Most relevant for
Individuals seeking to maintain intestinal barrier function or those at high risk of deficiency in regions with limited dietary access.

Potential benefits

  • Maintenance of Intestinal Lining.Unconfirmed. Critical for the differentiation of epithelial cells that form the gut barrier and the production of secretory IgA, the primary antibody protecting mucosal surfaces.
  • Severe Diarrhea Recovery.Reduces mortality risk and severity of diarrheal episodes in children at risk of deficiency and can accelerate recovery when diarrhea is a complication of measles.
  • Ulcerative Colitis Support.Unconfirmed. Preliminary evidence suggests high-dose supplementation may help reduce disease activity scores and support mucosal healing in adults with ulcerative colitis.

Limitations

  • Risk of Increased Diarrhea.Multiple large-scale trials in children have observed an increase in the prevalence and incidence of diarrhea following high-dose supplementation.
  • Status-Dependent Efficacy.Benefits for digestive health are primarily seen in those with existing deficiency; no clear evidence supports improved digestion in well-nourished individuals.
  • Pathogen-Specific Responses.Impact may vary by infection type; research indicates it may shorten certain bacterial infections while potentially lengthening others, such as Giardia.
Things to consider

Excessive intake can cause gastrointestinal manifestations, liver injury, and neurological symptoms; megadoses should be avoided unless medically supervised for deficiency.

Study evidence

69 studies

Vitamin A supports the intestinal lining, and supplementation can reduce severe diarrhea-related outcomes in some at-risk children. However, effects on diarrhea are inconsistent, some regimens have increased it, and the evidence does not establish better everyday digestion from extra Vitamin A in well-nourished people.

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Immunity
Immunity
Impact
Highest effect
Typical dose:900–3000 mcg

Critical for the health of mucosal surfaces in the respiratory tract and gut, which are the body's first line of defense. Vitamin A is also vital for the proper function of T-cells, B-cells, and Natural Killer cells, making it essential for both innate and adaptive immunity.

Focuses on
Immune NutrientsSeasonal DefenseAirways
Most relevant for
Individuals in regions with prevalent vitamin A deficiency or children managing specific infectious illnesses like measles.

Potential benefits

  • Immune Cell Support.Supports the production and function of T-cells and lymphocytes, which are critical for coordinating the body's response to infection.
  • Respiratory Recovery.May reduce the duration and severity of respiratory symptoms and complications in children, particularly when baseline levels are low or during specific illnesses.
  • Vaccine Response.Supplementation has been shown to improve antibody responses to certain immunizations, such as tetanus or hepatitis B, in populations with marginal deficiency.

Limitations

  • Limited Benefit if Status is Adequate.Research indicates no significant boost to immunity or infection prevention for individuals who already maintain sufficient vitamin A levels through diet.
  • Inconsistent Prevention.Evidence is mixed regarding its ability to prevent infections; some meta-analyses show no significant link between vitamin A status and the risk of recurrent respiratory infections.
  • Population Specific Risks.High-dose supplementation has been observed to reduce certain immune cell counts in older adults and may transiently alter immune development in newborns.
Things to consider

Excessive intake can be toxic and may lead to birth defects if taken during pregnancy; some studies also indicate high doses may negatively impact immune markers in older populations.

Study evidence

107 studies

Vitamin A supports normal immune function, and supplementation can help in settings of deficiency or particular childhood illnesses. The available research does not show a general immunity boost in people with adequate status; infection outcomes and immune responses vary, and some studies report unfavorable immune changes.

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Eye Health
Eye Health
Impact
High effect
Typical dose:2500–5000 IU

Vitamin A's role in forming rhodopsin is undisputed and essential. However, deficiency is rare in developed nations, and high-dose supplementation carries a risk of toxicity. The AREDS trials replaced its precursor, beta-carotene, due to risks in smokers.

Focuses on
RetinaNight Vision
Most relevant for
Individuals with inadequate dietary intake or those seeking to maintain dark-adaptation speed and low-light visual sensitivity.

Potential benefits

  • Night Vision Recovery.Essential for the formation of rhodopsin, a protein that allows the eyes to detect light; supplementation restores night vision in individuals with low vitamin A status.
  • Ocular Surface Protection.Supports the health of corneal and conjunctival tissues, helping to prevent dryness and the structural damage associated with xerophthalmia.
  • Retinal Dark Adaptation.Clinical research suggests that supplemental retinol can improve the speed at which rods adapt to darkness and support retinal sensitivity markers.

Limitations

  • No Benefit for Normal Status.In individuals with adequate dietary intake, additional supplementation has not been proven to improve general eyesight or prevent common age-related vision loss.
  • Uncertain Visual Preservation.Systematic reviews of conditions like retinitis pigmentosa indicate that vitamin A may not effectively preserve visual acuity or slow the progression of functional vision loss.
  • Delivery Method Differences.Certain ocular benefits for dry eye were specifically observed with specialized topical eye drops, which may not translate to oral supplementation.
Things to consider

High-dose supplementation carries a risk of toxicity and its precursor, beta-carotene, has been linked to increased health risks for smokers.

Study evidence

65 studies

Vitamin A supports normal vision, and supplementation can prevent deficiency-related night blindness and eye damage in at-risk populations. This benefit does not mean extra vitamin A improves eyesight when needs are already met; evidence for treating other eye diseases is mixed.

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Bone Health
Bone Health
Impact
Moderate effect
Typical dose:700–1500 mcg

Vitamin A, as retinoic acid, is essential for normal skeletal development and maintenance. It regulates the differentiation of bone cells, ensuring a healthy balance in the bone turnover process. Both deficiency and excess can negatively impact bone health, making adequate but not excessive intake important.

Focuses on
Bone DensityBone Remodeling
Most relevant for
Individuals aiming to maintain skeletal health through a balanced diet while avoiding excessive preformed vitamin intake.

Potential benefits

  • Skeletal Development Support.Unconfirmed. Vitamin A is essential for normal bone cell differentiation and remodeling, although research does not confirm that taking extra amounts provides any additional bone-strengthening benefits for healthy adults.
  • Bone Density Maintenance.Unconfirmed. Adequate intake is associated with higher bone mineral density in some populations with low baseline levels, but it is unproven whether supplementation improves bone mass in well-nourished individuals.

Limitations

  • Increased Hip Fracture Risk.Multiple meta-analyses and large cohort studies associate high intake of preformed retinol with a significantly increased risk of hip fractures, particularly in postmenopausal women.
  • Narrow Optimal Range.Research suggests a U-shaped relationship where both very low and very high blood retinol levels are linked to increased fracture risk, making excessive supplementation potentially counterproductive.
  • Retinol vs Carotenoids.The adverse effects on bone are primarily linked to preformed retinol from animal sources and supplements; plant-derived beta-carotene generally shows neutral or protective associations.
Things to consider

Excessive intake of preformed Vitamin A (retinol) from supplements or animal sources may increase fracture risk and impair bone formation. Plant-based carotenoids are generally preferred for maintaining vitamin A status without these skeletal risks.

Study evidence

56 studies

Vitamin A is involved in bone development, but taking extra does not have an established bone-health benefit. Higher retinol intake or blood levels have been linked with hip fractures in some research, while other findings are neutral and plant-derived carotenoids show different associations.

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Hair Health
Hair Health
Impact
Situational effect
Typical dose:700–3000 mcg

Vitamin A plays a crucial role in cell growth, including hair, the fastest-growing tissue in the human body. It also aids skin glands in making sebum, an oily substance that moisturizes the scalp and keeps hair healthy. However, both deficiency and excess can cause hair loss, so proper dosage is critical.

Focuses on
Growth CycleScalp Health
Most relevant for
Individuals managing specific inflammatory scalp conditions or using topical hair treatments under medical supervision.

Potential benefits

  • Scalp Sebum Production.Unconfirmed. Helps skin glands produce sebum to naturally moisturize the scalp, though evidence for general supplementation improving hair quality is limited.
  • Clinical Hair Management.Prescription vitamin A derivatives have shown efficacy in stabilizing inflammatory and scarring hair loss conditions like frontal fibrosing alopecia.
  • Synergy with Treatments.Topical retinoids may enhance the scalp's response to other treatments, such as minoxidil, by upregulating specific follicular enzymes.

Limitations

  • Supplement vs. Medication.Most research focuses on high-dose prescription retinoids; these findings do not necessarily translate to benefits from standard dietary supplements.
  • Risk of Shedding.Systemic retinoid use and excessive intake are frequently linked to telogen effluvium, a form of temporary hair shedding.
  • Lack of General Evidence.There is no robust evidence that supplemental vitamin A improves hair growth or thickness in individuals who are not deficient.
Things to consider

Excessive vitamin A intake is a known cause of hair loss. Do not exceed the recommended daily allowance for hair health unless specifically directed by a healthcare provider.

Study evidence

13 studies

The supplied research does not establish vitamin A supplements as a way to improve hair growth. Favorable findings mostly involve prescription retinoids for specific hair disorders, while excessive vitamin A and some retinoid treatments are associated with hair shedding.

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Skin Health
Skin Health
Impact
Situational effect
Typical dose:2500–10000 IU

Vitamin A is essential for normalizing skin cell proliferation and differentiation. Its derivatives (retinoids) are a cornerstone for treating acne by preventing clogged pores. It also stimulates collagen production, making it effective for reducing wrinkles, but should be used with caution due to potential toxicity at high doses.

Focuses on
FirmnessSun ProtectionClear SkinWound Healing
Most relevant for
Individuals looking to address signs of aging or uneven skin texture through topical applications.

Potential benefits

  • Reduces signs of aging.Topical vitamin A derivatives like tretinoin and retinol are clinically shown to reduce the appearance of fine lines and wrinkles by stimulating collagen synthesis and remodeling skin structure.
  • Improves skin texture.Retinoids help normalize skin cell proliferation and differentiation, which can lead to smoother skin, more even tone, and improved epidermal thickness.
  • Oral skin support.Unconfirmed. While essential for normal skin maintenance, the benefit of oral vitamin A supplements for improving skin appearance in healthy individuals is unproven and lacks consistent clinical support.

Limitations

  • Variable cosmetic efficacy.Evidence for over-the-counter retinol is less consistent than prescription versions, with some clinical trials showing major methodological flaws or no significant difference from a placebo.
  • Localized irritation.Topical application frequently causes side effects such as redness, scaling, dryness, and burning, which may limit tolerability for those with sensitive skin.
  • Limited oral evidence.High-quality research does not support the use of oral vitamin A for preventing skin cancer in immunocompetent adults, and high dietary intake may not correlate with lower cancer risk.
Things to consider

Topical retinoids can increase skin sensitivity to UV light and should be used with sunscreen. High doses of oral vitamin A can be toxic and should only be taken under medical supervision.

Study evidence

106 studies

Vitamin A derivatives applied to the skin can improve acne and signs of sun-related aging, with stronger evidence for prescription retinoids than cosmetic retinol. These findings do not establish similar benefits from oral vitamin A supplements, and topical products can cause irritation.

View goal

Studies

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Sources

Up to five highest-ranked published examples per goal. Study counts and charts include all published studies for the connection.

  1. Dietary vitamin A intake and the incidence of diarrhea and respiratory infection among Sudanese children.
    Fawzi WW; Herrera MG; Willett WC; Nestel P; el Amin A; Mohamed KA · The Journal of nutrition · 1995
    Cohort study28,753 participantsGut Health
  2. Vitamin A supplementation decreases disease activity index in patients with ulcerative colitis: A randomized controlled clinical trial.
    Masnadi Shirazi K; Nikniaz Z; Masnadi Shirazi A; Rohani M · Complementary therapies in medicine · 2019
    Randomized trial150 participantsGut Health
  3. The effects of vitamin A supplementation on the morbidity of children born to HIV-infected women.
    Coutsoudis A; Bobat RA; Coovadia HM; Kuhn L; Tsai WY; Stein ZA · American journal of public health · 1995
    Randomized trial118 participantsGut Health
  4. A randomized, controlled trial of vitamin A in children with severe measles.
    Hussey GD; Klein M · The New England journal of medicine · 1990
    Randomized trial189 participantsGut Health
  5. Vitamin A supplementation reduces the monocyte chemoattractant protein-1 intestinal immune response of Mexican children.
    Long KZ; Santos JI; Estrada Garcia T; Haas M; Firestone M; Bhagwat J; Dupont HL; Hertzmark E; Rosado JL; Nanthakumar NN · The Journal of nutrition · 2006
    Randomized trial127 participantsImmunityGut Health
  6. Depressed immune response to tetanus in children with vitamin A deficiency.
    Semba RD; Muhilal; Scott AL; Natadisastra G; Wirasasmita S; Mele L; Ridwan E; West KP; Sommer A · The Journal of nutrition · 1992
    Randomized trial236 participantsImmunity
  7. Impact of a single megadose of vitamin A at delivery on breastmilk of mothers and morbidity of their infants.
    Roy SK; Islam A; Molla A; Akramuzzaman SM; Jahan F; Fuchs G · European journal of clinical nutrition · 1997
    Randomized trial50 participantsImmunity
  8. Vitamin A supplementation reduces measles morbidity in young African children: a randomized, placebo-controlled, double-blind trial.
    Coutsoudis A; Broughton M; Coovadia HM · The American journal of clinical nutrition · 1991
    Randomized trial60 participantsImmunity
  9. Vitamin A supplementation enhances specific IgG antibody levels and total lymphocyte numbers while improving morbidity in measles.
    Coutsoudis A; Kiepiela P; Coovadia HM; Broughton M · The Pediatric infectious disease journal · 1992
    Randomized trial60 participantsImmunity
  10. A randomized trial of vitamin A and vitamin E supplementation for retinitis pigmentosa.
    Berson EL; Rosner B; Sandberg MA; Hayes KC; Nicholson BW; Weigel-DiFranco C; Willett W · Archives of ophthalmology (Chicago, Ill. : 1960) · 1993
    Randomized trial601 participantsEye Health
  11. Efficacy and safety of retinol palmitate ophthalmic solution in the treatment of dry eye: a Japanese Phase II clinical trial.
    Toshida H; Funaki T; Ono K; Tabuchi N; Watanabe S; Seki T; Otake H; Kato T; Ebihara N; Murakami A · Drug design, development and therapy · 2018
    Randomized trial66 participantsEye Health
  12. Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age.
    Imdad A; Mayo-Wilson E; Haykal MR; Regan A; Sidhu J; Smith A; Bhutta ZA · The Cochrane database of systematic reviews · 2022
    Meta-analysis1,223,856 participants47 studies pooledEye Health
  13. Vitamin A supplementation improves retinal function in infants at risk of retinopathy of prematurity.
    Mactier H; McCulloch DL; Hamilton R; Galloway P; Bradnam MS; Young D; Lavy T; Farrell L; Weaver LT · The Journal of pediatrics · 2012
    Randomized trial89 participantsEye Health
  14. Effect of short-term, high-dose retinol on dark adaptation in aging and early age-related maculopathy.
    Owsley C; McGwin G; Jackson GR; Heimburger DC; Piyathilake CJ; Klein R; White MF; Kallies K · Investigative ophthalmology & visual science · 2006
    Randomized trial104 participantsEye Health
  15. Evaluating the Protective Role of Vitamin A Supplementation in Periodontal Health: A Comprehensive Systematic Review and Meta-Analysis.
    Luca MM; Buzatu R; Bumbu BA · Journal of clinical medicine · 2024
    Meta-analysisBone Health
  16. Dietary vitamin A intake and bone health in the elderly: the Rotterdam Study.
    de Jonge EA; Kiefte-de Jong JC; Campos-Obando N; Booij L; Franco OH; Hofman A; Uitterlinden AG; Rivadeneira F; Zillikens MC · European journal of clinical nutrition · 2016
    Cohort study5,288 participantsBone Health
  17. Vitamin A and its dervatives effect on bone mineral density, a systematic review.
    Khojah Q; AlRumaihi S; AlRajeh G; Aburas A; AlOthman A; Ferwana M · Journal of family medicine and primary care · 2022
    Systematic review8 studies pooledBone Health
  18. Association of vitamins with bone mineral density and osteoporosis measured by dual-energy x-ray absorptiometry: a cross-sectional study.
    Wang Q; Yu H; Kong Y · BMC musculoskeletal disorders · 2024
    Cross-sectional study1,536 participantsBone Health
  19. Association of dietary consumption and serum levels of vitamin A and β-carotene with bone mineral density in Chinese adults.
    Chen GD; Zhu YY; Cao Y; Liu J; Shi WQ; Liu ZM; Chen YM · Bone · 2016
    Cohort study3,154 participantsBone Health
  20. Topical tretinoin for hair growth promotion.
    Bazzano GS; Terezakis N; Galen W · Journal of the American Academy of Dermatology · 1986
    Non-randomized trial56 participantsHair Health
  21. A review of isotretinoin in the treatment of frontal fibrosing alopecia.
    Shahpar A; Nezhad NZ; Sahaf AS; Ahramiyanpour N · Journal of cosmetic dermatology · 2024
    Systematic review232 participants15 studies pooledHair Health
  22. Efficacy of Isotretinoin and Acitretin in Treatment of Frontal Fibrosing Alopecia: Retrospective Analysis of 54 Cases.
    Rakowska A; Gradzińska A; Olszewska M; Rudnicka L · Journal of drugs in dermatology : JDD · 2018
    Cohort study54 participantsHair Health
  23. Systemic Treatments for Lichen Planopilaris and Frontal Fibrosing Alopecia: A Retrospective Study of 315 Patients.
    Willaert M; Van Dongen T; Dikrama P; Nijsten T; Hijnen D; Waalboer-Spuij R · Acta dermato-venereologica · 2025
    Cohort study315 participantsHair Health
  24. Tretinoin enhances minoxidil response in androgenetic alopecia patients by upregulating follicular sulfotransferase enzymes.
    Sharma A; Goren A; Dhurat R; Agrawal S; Sinclair R; Trüeb RM; Vañó-Galván S; Chen G; Tan Y; Kovacevic M; Situm M; McCoy J · Dermatologic therapy · 2020
    Single-arm trialHair Health
  25. Efficacy and Tolerability of Topical 0.1% Stabilized Bioactive Retinol for Photoaging: A Vehicle-Controlled Integrated Analysis.
    Farris P; Berson D; Bhatia N; Goldberg D; Lain E; Mariwalla K; Zeichner J; Miller D; McGuire T; Kizoulis M · Journal of drugs in dermatology : JDD · 2024
    Meta-analysis471 participants6 studies pooledSkin Health
  26. Tensile properties and contours of aging facial skin. A controlled double-blind comparative study of the effects of retinol, melibiose-lactose and their association.
    Piérard-Franchimont C; Castelli D; Cromphaut IV; Bertin C; Ries G; Cauwenbergh G; Piérard GE · Skin research and technology : official journal of International Society for Bioengineering and the Skin (ISBS) [and] International Society for Digital Imaging of Skin (ISDIS) [and] International Society for Skin Imaging (ISSI) · 2016
    Randomized trial120 participantsSkin Health
  27. Antiaging action of retinol: from molecular to clinical.
    Bellemère G; Stamatas GN; Bruère V; Bertin C; Issachar N; Oddos T · Skin pharmacology and physiology · 2009
    Randomized trial48 participantsSkin Health
  28. An Updated Review of Topical Tretinoin in Dermatology: From Acne and Photoaging to Skin Cancer.
    Balado-Simó P; Morgado-Carrasco D; Gómez-Armayones S; López-Ferrer A; Barco D; Ferrándiz-Pulido C; Podlipnik S · Journal of clinical medicine · 2025
    Narrative reviewSkin Health
  29. Novel Cyclized Hexapeptide-9 Outperforms Retinol Against Skin Aging: A Randomized, Double-Blinded, Active- and Vehicle-Controlled Clinical Trial.
    Chang H; Tao K; Yang Y; Wang Y; Ge M; Wang X; Tang S; Yu H · Journal of cosmetic dermatology · 2025
    Randomized trialSkin Health