Vitamin A
Fat-soluble vitaminsYour intake
What each level of vitamin a does
Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.
- Severely lowYOU ARE HERE0 mcg – 297 mcg
Well below target. Risk of deficiency symptoms tied to vision · immunity.
- Insufficient297 mcg – 900 mcg
Below the recommended daily target. Long-term adequacy not assured.
- Adequate900 mcg – 1350 mcg
Daily target met. Standard nutritional support for vision · immunity.
- Therapeutic1350 mcg – 1800 mcg
Common for specific health goals. Check the evidence for your situation before sustaining this level.
- High1800 mcg – 3000 mcg
Approaching the tolerable upper limit. Monitor and consider clinical guidance.
- Over upper limit3000 mcg – +
Above the tolerable upper limit. Risk of adverse effects — back off or consult a clinician.
Overview
Fat-soluble vitamin essential for vision, immunity, reproduction, and the integrity of epithelial tissue. Exists in two pools: preformed retinoids from animal foods (immediately usable) and provitamin carotenoids from plants (converted on demand and rate-limited by body status, which is why carrots don't cause toxicity but high-dose retinol can).
Functions
- ●Forms retinal — the photopigment in rod and cone cells
- ●Regulates gene expression of epithelial differentiation
- ●Maintains mucosal barriers in gut, lung, and skin
- ●Required for T- and B-cell proliferation during immune response
Mechanism
Retinol is oxidised to retinal (vision) or retinoic acid (gene regulation). Retinoic acid binds nuclear RAR/RXR receptors that act as transcription factors for ~500 genes governing differentiation. Beta-carotene is cleaved by BCO1 in enterocytes — cleavage efficiency drops as retinol stores rise, providing a built-in toxicity buffer.
Benefits
- ●Prevents night blindness and xerophthalmia
- ●Reduces measles mortality in deficient children (WHO supplementation programs)
- ●Supports epithelial wound healing and skin renewal
- ●Topical retinoids (prescription) treat acne and photoaging
Deficiency
Globally common in regions with limited animal-source food and orange produce; rare in the US outside of fat-malabsorption disorders. Earliest sign is impaired dark adaptation.
- ●Night blindness, Bitot's spots, xerophthalmia
- ●Dry skin and hyperkeratosis (follicular bumps)
- ●Increased respiratory and GI infection rates
- ●Stunted growth in children
- ●Premature infants
- ●Cystic fibrosis, biliary atresia, pancreatic insufficiency
- ●Strict vegan diets without carotenoid-rich produce
Excess
Preformed retinol is teratogenic and hepatotoxic in chronic excess. Carotenoid intake does not cause true hypervitaminosis A — only harmless skin yellowing (carotenodermia).
- ●Headache, nausea, dizziness (acute)
- ●Hair loss, dry cracked skin, bone pain (chronic)
- ●Hepatic fibrosis, hypercalcemia
- ●Congenital malformations if exposed in early pregnancy
Forms
- Retinol / retinyl palmitate / retinyl acetatePreformed, immediately bioavailable, contributes to UL
- Beta-caroteneProvitamin, conversion-regulated, no toxicity risk
- Alpha-carotene, beta-cryptoxanthinOther provitamin carotenoids, lower retinol yield
- Mixed carotenoidsWhole-food spectrum incl. lutein/zeaxanthin (eye, not retinol)
Food sources
- Beef liver (cooked) · 3 oz6,500 mcg RAE
- Sweet potato (baked, with skin) · 1 medium1,400 mcg RAE
- Cooked spinach · 1 cup950 mcg RAE
- Cooked carrots · 1 cup1,300 mcg RAE
- Cantaloupe · 1 cup cubed270 mcg RAE
- Egg yolk · 1 large75 mcg RAE
Supplement forms
Look for products that deliver most of the dose as beta-carotene plus a small amount of retinyl palmitate or retinyl acetate. Avoid supplements above 100% DV from preformed retinol, especially during pregnancy.
Bioavailability
Absorbed with dietary fat in mixed micelles via SR-BI and CD36 transporters. Cooking and oil pairing improve carotenoid extraction from plants (cooked carrots in olive oil ≫ raw). Smokers and former smokers should avoid high-dose beta-carotene supplementation (CARET/ATBC trials showed lung-cancer increase).
Longevity relevance
Adequate but not high. The healthy range is narrow: deficiency drives infection and blindness; excess accelerates osteoporosis and liver injury. Whole-food carotenoid intake (lutein, zeaxanthin) is more consistently associated with reduced AMD and all-cause mortality than supplemental retinol.
Relationships
- Zinc · Required for retinol-binding protein synthesis; zinc deficiency mimics vitamin A deficiency
- Dietary fat · Carotenoid bioavailability rises 3–6× with ≥3–5 g co-ingested fat
- Vitamin E · Antioxidant cooperation reduces carotenoid auto-oxidation in plasma
- Alcohol (chronic) · Depletes hepatic retinol stores and amplifies hepatotoxicity at lower retinol doses
- Orlistat / bile-acid sequestrants · Block fat absorption, reduce uptake of all fat-soluble vitamins
- Mineral oil laxatives · Trap fat-soluble vitamins in unabsorbed lipid phase
References
About Vitamin A
Retinal function, immune response, skin and mucous membrane health.
- Role
- Vision · immunity
- Daily target
- 900 mcg (DV)
- Upper limit
- 3000 mcg
- Also called
- vitamin a, retinol, retinyl palmitate, retinyl acetate, beta-carotene, beta carotene
The mechanisms and systems this nutrient feeds. Click any to drill into what runs on it.
Top food sources of Vitamin A
Whole foods that contribute meaningfully (≥10% DV per 100 g serving). Click any food to see its full nutrient profile and what else it brings to the table.