Vitamin A
fat-soluble
Key Takeaways
- Fat-soluble vitamin with an FDA daily value of 900 mcg RAE for adults
- Plays key roles in wound healing, epithelial growth, collagen synthesis, and immune modulation
- Deficiency remains the leading cause of preventable blindness worldwide, particularly in developing countries
- Excessive intake during early pregnancy may cause teratogenic effects; supplementation must be carefully managed
- Available in preformed retinol (animal sources) and provitamin A carotenoids (plant sources)
Evidence Spectrum
15 studies reviewed →Wound Healing
Vitamin A stimulates epithelial growth, fibroblasts, granulation tissue, angiogenesis, and collagen synthesis in all stages of wound healing. It is commonly used to offset the effects of corticosteroids on wound repair. Evidence is primarily from animal studies and expert opinion; rigorous human trials are lacking.35
Fetal Development and Pregnancy Outcomes
Vitamin A is essential for morphological and functional fetal development. Deficiency during pregnancy is a public health issue in developing countries, linked to night blindness and adverse outcomes. However, excess intake is teratogenic in the first 60 days after conception.168
Oral Health
Lower vitamin A intake has been associated with decreased oral epithelial development, impaired tooth formation, enamel hypoplasia, and periodontitis.7
15
Studies Reviewed
900 mcg RAE
RDA (Adults (general, per FDA daily value))
3000 mcg RAE
Upper Limit
fat-soluble
Solubility
Role in the Body
Vitamin A is a group of fat-soluble retinoids essential for multiple physiological processes. It functions as a hormone through retinoic acid receptors, altering the activity of multiple cell lines and exerting systemic metabolic effects via its interrelationship with thyroid, insulin, and corticosteroid hormones (pmid:31697447). Pancreatic vitamin A levels are critical for retinoid signaling and normal glucose control. Vitamin A plays a vital role in all stages of wound healing, stimulating epithelial growth, fibroblast activity, granulation tissue formation, angiogenesis, collagen synthesis, epithelialization, and fibroplasia (pmid:31697447). Both local and systemic supplementation have been shown to increase dermal collagen deposition. It is also essential for morphological and functional fetal development and ocular integrity (pmid:30909386). Beyond wound healing, vitamin A is important for oral health, with lower intake associated with decreased oral epithelial development, impaired tooth formation, enamel hypoplasia, and periodontitis (pmid:31940621). Vitamin A deficiency impairs immune function and is more common during infection, while supplementation reduces severe morbidity and mortality from infectious diseases (pmid:31697447).
- Vision and ocular integrity
- Immune system modulation and defense against infections
- Wound healing: epithelial growth, collagen synthesis, angiogenesis
- Fetal development and morphogenesis
- Gene expression regulation via retinoic acid receptors
- Oral health: epithelial development and tooth formation
- Skin integrity and cellular differentiation
Supplement Forms
Retinyl palmitate
RecommendedBioavailability: 70%
Common preformed vitamin A in supplements and fortified foods; well-absorbed with dietary fat
Retinyl acetate
RecommendedBioavailability: 65%
Another common supplemental form of preformed vitamin A
Beta-carotene
RecommendedBioavailability: 30%
Provitamin A carotenoid from plant sources; lower conversion efficiency but lower toxicity risk
Retinol
Bioavailability: 75%
Pure retinol is highly bioavailable but carries higher toxicity risk at elevated doses
Food Sources
Milk, dry, nonfat, instant, with added vitamin A and vitamin D (2360 IU per 100g, USDA fdcId:171272)
Milk, dry, nonfat, regular, with added vitamin A and vitamin D (2180 IU per 100g, USDA fdcId:172195)
Cheese, pasteurized process, American, vitamin D fortified (300 UG per 100g, USDA fdcId:325198)
Milk, canned, evaporated, nonfat, with added vitamin A and vitamin D (394 IU per 100g, USDA fdcId:170878)
Milk, nonfat, fluid, with added vitamin A and vitamin D (204 IU per 100g, USDA fdcId:171269)
Hass avocado (43 mcg per half fruit, pmid:23638933)
Deficiency
Prevalence: Vitamin A deficiency remains the leading cause of preventable blindness worldwide, particularly in developing countries. It is a public health issue for pregnant women in most developing nations (pmid:30909386).
Symptoms:
- Night blindness
- Xerophthalmia (dry eyes)
- Impaired immune function and increased susceptibility to infections
- Enamel hypoplasia and impaired tooth formation
- Decreased oral epithelial development
- Skin changes (hyperkeratosis)
- Impaired wound healing
Risk Factors:
- Low dietary intake of animal products and carotenoid-rich vegetables
- Pregnancy and lactation (increased requirements)
- Infants and children in developing countries
- Malabsorption conditions affecting fat absorption
- Infection (increases vitamin A utilization)
Safety & Interactions
Possible Side Effects:
- • Acute toxicity: nausea, headache, dizziness, blurred vision
- • Chronic toxicity: liver damage, bone abnormalities, skin changes
- • Hypervitaminosis A can be critical and even result in death (pmid:31697447)
Drug Interactions:
- • Corticosteroids: vitamin A supplementation is used to offset steroid-induced impairment of wound healing
- • Retinoid medications (isotretinoin, tretinoin): combined use increases toxicity risk
- • Thyroid, insulin, and corticosteroid hormones: vitamin A modulates these hormonal pathways
Contraindications:
- • Early pregnancy (first 60 days post-conception) at high doses due to teratogenic effects (pmid:30909386)
- • Liver disease (impaired vitamin A metabolism and storage)
- • Concurrent use of retinoid medications
Frequently Asked Questions
What is the recommended daily intake of Vitamin A?
The FDA daily value for Vitamin A is 900 mcg RAE for adults. Requirements are higher during pregnancy and lactation.
Can you take too much Vitamin A?
Yes. Chronic excessive intake can cause liver damage, bone abnormalities, and in severe cases, death. The tolerable upper intake level is 3000 mcg RAE for adults. High doses in early pregnancy are teratogenic.
What are the best food sources of Vitamin A?
Fortified dairy products (milk, cheese), liver, eggs, and carotenoid-rich fruits and vegetables like sweet potatoes, carrots, and spinach are good sources.
What are the symptoms of Vitamin A deficiency?
Night blindness is the hallmark early symptom. Other signs include dry eyes, impaired immune function, skin changes, and poor wound healing. Deficiency is the leading cause of preventable blindness worldwide.
Research Sources
15 peer-reviewed studies analyzed from PubMed. 8 directly cited in this review.