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Vitamin A

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Vitamin A

Info
Dosage (RDI)
  • Females: 700mcg/day
  • Males: 900mcg/day
  • Upper level: 3000mcg/day
Absorption location
  • Small intestine. Mucosal cells.
Forms
  • Retinol (true vitamin A)
  • carotenoids (pre-vitamin A) (not always converted to true vitamin A well)
Cofactors Synergistic nutrients: Vitamins B1, B3, C, D, E, Mg, Se, Mn, K, P, Carotenoids, I, Tyrosine, Zn.
Storage Sites
  • Liver
Uses
Deficiency symptoms
  • Night blindness
  • Keratinisation of epithelial surfaces (causing them to dry and harden)
  • Poor dental health
  • Compromised immune system
  • Reduced reproductive capabilities
Causes of deficiency
Primary: 
  • Prolonged dietary deprivation of vitamin A
Secondary: When absorption, storage, transport and conversion are effected.
  • Celiac
  • Cystic fibrosis
  • Pancreatic disease
  • Obstruction of bile ducts
  • Giardiasis 
  • Diabetes
  • Duodenal bypass
  • Congenital partial obstruction of jejunum
Therapeutic uses
  • Cancer prevention and adjunct therapy
  • Infections
  • Skin (internal and topical)
  • Asthma 
  • Lung function in cystic fibrosis
  • Healing mucosa
Sources
Food
  • Fish liver oil
  • Liver
  • Red meat
  • Eggs (yolk)
  • Fish
  • Milk
  • Butter
  • Cream.
*Cooking can destroy up to 40% vitamin A content in food.
Roles
Roles
  • Antioxidant
  • Growth and development
  • Immune function
  • Maintenance of epithelial cells
  • Vision
  • Cancer prevention
  • Cognitive development and function
  • Sperm health
More
Contraindications
  • Doses greater than 10,000 IU a day for prolonged time is cautioned.
  • Liver, kidney disease, alcoholism, severe osteoporosis
    • Use supplementation with caution.
  • Vitamin A promotes aortic valve calcification
Interactions
  • Oral contraceptive pill (OCP) – Increased levels of vitamin A occur due to longer storage in the liver.
  • HMG-CoA reductase inhibitors (statins) – Increase serum vitamin A. Monitor patients taking these
  • Chemo-therapeutics – adjunctive therapy may improve drug response. Use only under professional supervision
  • Isotretinoin
  • Colchicine
  • Cholestyramine – Reduces vitamin A absorption
  • Orlistat – Reduces vitamin A levels
  • Tetracyclines – Adjunctive therapy can increase drug side effects
Toxicity Symptoms
  • Nausea
  • Vomiting
Braun, L., & Cohen, M. (2015). Herbs and Natural Supplements, Volume 2. Elsevier Health Sciences.
Hechtman, L. (2018). Clinical Naturopathic Medicine. Elsevier Health Sciences. 
Osiecki, H. (2010). The Nutrient Bible (8th ed.). Bio Concepts Publishing.
Categories: Nutrition