Vitamin A (Retinol & Carotenoids)

Summary

Vitamin A includes both preformed retinol (animal sources) and provitamin A carotenoids (plant sources).
It is essential for night vision, cell growth, skin health, and immune function.
⚠️ Excess intake, especially from retinol, can be toxic and teratogenic during pregnancy.

🟢 What It Does (Strong Evidence)

Vision: Vital for rhodopsin and night vision.
Immunity: Supports epithelial barriers and immune cell differentiation.
Skin: Promotes cell regeneration and differentiation (proven for topical retinoids).
Deficiency: Rapidly corrected symptoms (xerophthalmia, keratinization, immune weakness).

🟡 What’s Unclear (Gray Areas)

Oral supplementation benefits beyond deficiency are limited and inconsistent.
Anti-aging effects are not proven for oral intake (topical use only).
Cancer data are mixed: beta-carotene supplements increase lung risk in smokers, while carotenoid-rich foods remain beneficial.

🔴 What It Doesn’t Do

Does not rejuvenate the skin orally.
Does not prevent cancer through supplementation.
Does not replace a balanced diet rich in colorful vegetables and moderate animal sources.

Intake & Dosage (Non-prescriptive)

Recommended intakes (adults):
- Women ≈ 700 µg RAE/day, Men ≈ 900 µg RAE/day.
- 1 µg RAE = 1 µg retinol ≈ 12 µg dietary beta-carotene.
Upper limit (UL): 3000 µg RAE/day for preformed retinol.
Supplementation: unnecessary with a balanced diet; prefer natural carotenoids.
Pregnancy: avoid retinol and liver; choose plant carotenoid sources instead.

💣 Upper Limit (UL)

Note: The upper limit is $3000 µg RAE/day (preformed retinol only) ($NIH / EFSA / Health Canada).
Exceeding this provides no benefit and may cause liver toxicity, bone loss, and teratogenic effects.
Does not apply to carotenoids from foods.

Safety

Hypervitaminosis A (retinol): headaches, nausea, bone pain, hepatic abnormalities.
Pregnancy: high risk of fetal malformations.
Smokers/ex-smokers: avoid beta-carotene supplements.

Risks & Interactions

Excess retinol → hepatotoxicity, headaches, bone disorders; teratogenic during pregnancy.
Beta-carotene supplements discouraged in smokers/ex-smokers (lung risk signal).
⚠️ Retinoid medications (isotretinoin, acitretin): additive toxicity — avoid concurrent retinol supplementation.
Orlistat, cholestyramine, colestipol, and mineral oils reduce absorption of fat-soluble vitamins.

Quality Tips

Clear labeling: form (retinol vs carotenoid) and units in µg RAE.
Avoid high-dose supplements (>100% DV).
Prioritize colorful food sources: carrots, sweet potatoes, spinach, apricots, liver (in moderation).
If supplementing, choose low-dose mixed formulas (retinol + natural carotenoids).

Sources

$- https://ods.od.nih.gov/factsheets/VitaminA-Consumer/ - https://efsa.onlinelibrary.wiley.com/ - https://www.canada.ca/en/health-canada.html - https://pubmed.ncbi.nlm.nih.gov/

ODS/NIH — Vitamin A Fact Sheet
EFSA / Health Canada — Nutrient Reference Values (RAE, UL)