Vitamin A

Effects and Benefits

Core Identification

Common Names:
- Vitamin A
- Retinol (preformed vitamin A)
- Beta-carotene (provitamin A)
- The "Anti-Infective Vitamin"

Latin Name: N/A (not applicable for vitamins)

Category: Vitamin

Uses

Traditional Uses

• Night blindness treatment - Ancient Egyptians and Greeks recommended eating liver to restore night vision
• Skin healing - Traditional application of liver extracts for wound healing
• Infectious disease resistance - Historical use of cod liver oil to prevent respiratory infections

Modern Uses

• Vision Health - Essential for rhodopsin production and retinal function | Research quality: Strong
• Key findings: Retinol converts to visual purple (rhodopsin) in the retina, enabling light detection and dark adaptation

• Source citations: Brewer, Encyclopedia of Vitamins; Merck Manual Home Health Handbook

• Immune System Support - Maintains mucous membrane integrity and immune cell production | Research quality: Strong

• Key findings: Vitamin A is needed for production of immune cells lining respiratory and intestinal tracts; optimum intakes protect against viral infections including colds, influenza, and bronchitis

• Source citations: Brewer, Encyclopedia of Vitamins; Moline, Doctors Book of Natural Health Remedies

• Skin Health & Acne Treatment - Regulates skin cell turnover and sebaceous gland function | Research quality: Strong

• Key findings: Retinoids suppress growth of skin cells that clog oil glands; topical retinol products are proven to stimulate healthy cell turnover and collagen production

• Source citations: Lee, Put Your Best Face Forward; Moline, Doctors Book of Natural Health Remedies

• Growth & Development - Essential for fetal development and bone health | Research quality: Strong

• Key findings: Vitamin A is required for normal growth of limbs, heart, eyes, and ears during fetal development; maintains healthy bones and teeth

• Source citations: Brewer, Encyclopedia of Vitamins; Moline, Doctors Book of Natural Health Remedies

• Age-Related Macular Degeneration (AMD) - When combined with other antioxidants, may slow progression | Research quality: Moderate

• Key findings: The AREDS study found beta-carotene with vitamins C, E, and zinc reduced risk of vision loss by 25% in those with advanced AMD
• Source citations: Moline, Doctors Book of Natural Health Remedies

Active Compounds

Primary Active Ingredients:
- Retinol - The active preformed vitamin A found in animal sources; directly usable by the body for vision, immune function, and gene regulation
- Retinal (Retinaldehyde) - Metabolite of retinol essential for the visual cycle in the retina
- Retinoic Acid - Hormone-like form that binds to cell receptors and regulates gene expression for growth, development, and cell differentiation
- Beta-carotene - Most important provitamin A carotenoid; converted to retinol in the liver and intestinal cells (6 mcg beta-carotene ≈ 1 mcg retinol)
- Other Carotenoids - Alpha-carotene, cryptoxanthin, and others can also convert to vitamin A; lutein and zeaxanthin support eye health but don't convert to vitamin A

Dosage Information

Standard Dosage:
- Form: Food sources, supplements (capsule, softgel, liquid)
- Amount: 700-900 mcg RAE (2,310-3,000 IU) per day for adults
- Frequency: Daily
- Note: EC RDA is 800 mcg (2,664 IU)

Therapeutic Dosage:
- Form: Supplements containing beta-carotene (preferred) or mixed carotenoids
- Amount: Up to 1,500 mcg (5,000 IU) daily
- Purpose: General supplementation and immune support
- Duration: Ongoing with monitoring

Maximum Safe Dosage:
- Daily maximum: 3,000 mcg (10,000 IU) for adults (preformed vitamin A/retinol)
- Warning threshold: Doses above 10,000 IU daily for extended periods can cause toxicity; pregnant women should not exceed 3,000 mcg due to birth defect risks
- Note: Beta-carotene from food or supplements has no established upper limit as conversion to vitamin A is self-regulating

Bioavailability Notes:
- Preformed retinol from animal sources is readily absorbed (70-90%)
- Beta-carotene conversion is inefficient—only about 50% is converted to vitamin A
- Conversion efficiency decreases with low zinc status
- Fat enhances absorption of all vitamin A forms; take with a fat-containing meal

How to Take It

Timing:
- Best taken with meals containing dietary fat
- Morning or evening; no specific preference
- Consistent daily intake preferred over large intermittent doses

Synergies - What It Works Well With

Complementary Supplements:
1. Zinc - Required for vitamin A metabolism and transport; deficiency impairs vitamin A utilization | Enhances both absorption and function
2. Vitamin E - Works synergistically as antioxidants; vitamin E protects vitamin A from oxidation | Combined antioxidant protection
3. Vitamin C - Partner antioxidant that helps regenerate vitamin A after free radical neutralization | Enhanced antioxidant network
4. Vitamin D - Works together for bone health and immune function | Complementary effects on calcium metabolism and immunity
5. Lutein & Zeaxanthin - Fellow carotenoids that concentrate in the macula | Combined protection against AMD (as demonstrated in AREDS study)

Avoidance - What NOT to Combine With

Supplement Interactions:
1. High-dose beta-carotene supplements (in smokers) - Studies show increased lung cancer risk when smokers take high-dose synthetic beta-carotene supplements | Avoid supplementation in current smokers

Drug Interactions:
1. Retinoid medications (isotretinoin/Accutane, tretinoin) - Combined use causes additive toxicity and hypervitaminosis A | Potential consequence: Severe toxicity, increased intracranial pressure | Severity: Severe
2. Orlistat (weight loss drug) - Reduces absorption of fat-soluble vitamins | Potential consequence: Reduced vitamin A levels | Severity: Moderate
3. Cholestyramine/Colestipol (bile acid sequestrants) - Reduce absorption of fat-soluble vitamins | Potential consequence: Vitamin A deficiency | Severity: Moderate
4. Warfarin (blood thinner) - High vitamin A doses may enhance anticoagulant effect | Potential consequence: Increased bleeding risk | Severity: Moderate
5. Tetracycline antibiotics - Combined with high-dose vitamin A can increase intracranial pressure | Potential consequence: Severe headaches, vision problems | Severity: Severe

Food Interactions:
- Alcohol - Increases vitamin A toxicity risk; both are metabolized in the liver
- Very high liver consumption during pregnancy should be avoided due to concentrated vitamin A content

Safety Information

Contraindications:
- Pregnancy (high-dose preformed vitamin A) - doses above 3,000 mcg (10,000 IU) linked to birth defects, especially in first 7 weeks
- Liver disease - impairs vitamin A storage and metabolism, increasing toxicity risk
- Hypervitaminosis A - existing vitamin A toxicity
- Concurrent use of retinoid medications

Side Effects:
- Common (high doses): Dry skin, cracked lips, hair loss, headaches
- Less common: Bone and joint pain, nausea, vomiting, blurred vision
- Rare but serious: Liver damage, increased intracranial pressure, birth defects
- Carotenemia (excessive beta-carotene): Harmless yellow-orange discoloration of skin, particularly palms and soles

Long-Term Use:
- Preformed vitamin A (retinol): Long-term use above 1,500 mcg daily may increase fracture risk in postmenopausal women
- Beta-carotene: Generally safe for long-term use from food sources; supplement safety less certain in smokers
- Monitoring: Periodic liver function tests recommended for those taking high doses
- Cycle recommendations: Not typically cycled; maintain consistent moderate intake rather than high intermittent doses

Special Precautions:
- Surgery: No specific precautions, but inform healthcare provider of supplement use
- Pregnancy: Use pregnancy-specific supplements with little to no preformed vitamin A; beta-carotene preferred
- Breastfeeding: Vitamin A passes into breast milk; excessive intake may affect infant
- Elderly: May be at increased fracture risk from high preformed vitamin A intake
- Children: Particularly susceptible to toxicity; follow age-appropriate dosing strictly

Primary Uses At-a-Glance

Primary: Vision health, immune system support, skin health and acne, growth and development

Secondary: Age-related macular degeneration (with other antioxidants), wound healing, mucous membrane integrity

Sources

Local Library:
- Brewer, Sarah - TDT Encyclopedia of Vitamins
- Moyad, Mark - The Supplement Handbook
- Moline, Peg - The Doctors Book of Natural Health Remedies
- Merck - The Merck Manual Home Health Handbook
- Cordain, Loren - The Paleo Answer
- Stewart, Martha - Living the Good Long Life
- Weil, Andrew - Eating Well for Optimum Health
- Lust, John - The Natural Remedy Bible
- Lee, Sandra - Put Your Best Face Forward
- Galper, Amy - Plant-Powered Beauty

General Knowledge:
- NIH Office of Dietary Supplements
- National Eye Institute AREDS Study
- Standard nutritional and toxicology references