Vitamin A
Retinol / Beta-Carotene
Strong
Vitamin A is a fat-soluble vitamin essential for vision (especially night vision), immune system function, skin health, and cellular growth. It exists in two forms: preformed vitamin A (retinoids from animal sources) and provitamin A (carotenoids like beta-carotene from plants).
How It Works
Vitamin A functions through multiple mechanisms:
- Vision: Retinal (a form of vitamin A) combines with the protein opsin to form rhodopsin, the light-sensitive molecule in rod cells essential for night vision and low-light adaptation.
- Gene Expression: Retinoic acid binds to nuclear receptors (RAR and RXR) that regulate gene transcription, affecting cell growth, differentiation, and apoptosis.
- Immune Function: Supports the integrity of mucosal barriers and is critical for T-cell development and function. Often called the “anti-infective vitamin.”
- Skin Health: Promotes keratinocyte differentiation and sebum regulation, essential for healthy epithelial tissue.
Natural Food Sources
| Food | Amount per Serving |
|---|---|
| Beef liver | 6,582 mcg RAE per 3 oz |
| Sweet potato | 1,403 mcg RAE per medium |
| Spinach (cooked) | 573 mcg RAE per 1/2 cup |
| Carrots | 459 mcg RAE per 1/2 cup |
| Cantaloupe | 135 mcg RAE per 1/2 cup |
| Eggs | 80 mcg RAE per large egg |
Safety Information
Contraindications
- Pregnancy - high doses (>10,000 IU/day) are teratogenic and can cause birth defects
- Liver disease - vitamin A is stored in the liver and can worsen hepatotoxicity
- Smokers should avoid high-dose beta-carotene supplements (increased lung cancer risk)
Potential Side Effects
- Nausea and vomiting (acute toxicity) (rare)
- Headache and dizziness (uncommon)
- Dry, itchy skin (common)
- Hair loss (chronic high doses) (rare)
- Orange skin discoloration (beta-carotene, harmless) (common)
Disclaimer: The information provided is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare provider before starting any supplement regimen.