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Vitamin A (Retinol/Beta-Carotene)
Fat-soluble vitamin that maintains night vision, drives immune cell differentiation, and regulates skin turnover and cellular growth.
What the evidence says
Studies are split: Vitamin A helped in 7 of 16 cases, with the rest inconclusive or showing no benefit.
Most evidence is from high-quality meta-analyses and randomised trials published 2016–2026 with a typical study size of 773 participants.
Based on 46 studies · 22 meta-analyses · 7 RCTs · 768,119 total participants
Confidence
HighWhat the studies found
By outcome
See full supplement plans that include Vitamin A.
Vitamin A has an evidence score of 9/10 — very strong evidence based on 46 indexed studies, including 34 meta-analyses. Fat-soluble vitamin that maintains night vision, drives immune cell differentiation, and regulates skin turnover and cellular growth.
The commonly studied dose of Vitamin A is 2500-5000 IU daily (retinol); up to 25000 IU (beta-carotene). Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take Vitamin A is with meals. Take it with food. Vitamin A (retinol/retinyl esters) is a fat-soluble vitamin requiring bile acid emulsification and dietary fat for absorption via intestinal enterocytes.
Vitamin E
Likely helpsLipid-soluble antioxidant that shields cell membranes from oxidative damage — natural mixed tocopherols preferred over synthetic forms.
Biotin
Probably helpsCofactor for fatty acid synthesis and gluconeogenesis — strongest evidence for brittle nail syndrome and keratin infrastructure support.
Last reviewed May 2026 · evidence from 40 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Vitamin A is an essential fat-soluble vitamin that exists in two primary forms: preformed vitamin A (retinol, found in animal foods) and provitamin A carotenoids (like beta-carotene, found in plants). It's crucial for maintaining healthy vision (especially night vision), immune function, skin integrity, and cellular differentiation. Deficiency is rare in developed countries but can cause night blindness and immune dysfunction.
Essential for rhodopsin production
Maintains immune barriers and cell function
Regulates cellular growth and differentiation
How Vitamin A works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
2500-5000 IU daily (retinol); up to 25000 IU (beta-carotene)
Loading: Not required; avoid high doses
Take with food
| Form | Type |
|---|---|
| 💊Mixed carotenoids or low-dose retinyl palmitate | Recommended |
| 💊Beta-carotene (provitamin A) | Alternative |
| 💊Retinyl acetate | Alternative |
| 💧Cod liver oil | Alternative |
Beta-carotene is safer (no toxicity risk) but conversion varies. Preformed vitamin A is more reliable but has toxicity potential.
Minimum: 4 weeks
Optimal: 12 weeks
Cycling: Not required
Note: Fat-soluble vitamin; requires dietary fat for absorption. Beta-carotene is safer as body regulates conversion.
You can get vitamin a from these foods and drinks. Doses are typical per-serving estimates — actual content varies by brand, brew, cooking, etc.
18000 IU per piece
1 medium baked sweet potato. As beta-carotene (provitamin A); conversion to retinol varies by individual (1:2 to 1:24 ratio).
21000 IU per cup
1 cup raw chopped. Same beta-carotene → retinol caveat. Cook with fat to absorb more.
66000 IU per 3 ozs
3 oz cooked. Preformed retinol (no conversion needed). Don't exceed 1 serving/week if pregnant — vitamin A toxicity risk.
Dose-response data unavailable. The current published research for Vitamin A does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Maintained night vision and eye health
Enhanced immune defenses
Improved skin cell turnover
Fat-soluble; can accumulate to toxic levels
AVOID high-dose retinol; beta-carotene is safer
Avoid high-dose beta-carotene supplements
Do not combine; risk of vitamin A toxicity
May reduce absorption; take separately
Risk of vitamin A overdose, liver toxicity
Tip: Stay below 10,000 IU/day preformed vitamin A
Tip: Harmless; reduce dose if concerned
Vitamin A is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are hypervitaminosis A, skin yellowing (beta-carotene). Use caution if any of these apply to you: Pregnancy (high-dose retinol is teratogenic); Liver disease.
Vitamin C
Probably helpsHumans cannot synthesize this vitamin — required for collagen production, immune cell function, and iron absorption; athletes need more.
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