Vitamin A

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Vitamin A, or retinol, is a fat-soluble vitamin which means that it can be dissolved in the fat within your body. Vitamin A is known for its role in cell reproduction (cellular differentiation), vision, as well as embryotic and fetal development. A lesser known role of vitamin A is keeping the skin and mucous membranes in your nose, sinuses, and mouth functioning properly. Vitamin A additionally aids in immune system health, bone growth, reproduction, heart, lungs, and kidney function, and wound healing.

Vitamin A can originate from two sources: retinoids, which are animal sources, and carotenoids, which come from various plants. Carotenoids include beta-carotene which is converted to vitamin A within the body. Vitamin A deficiency is rare within industrialized countries, but can be recognized by symptoms such as dry eyes, night blindness, diarrhea, and skin issues. The most common symptom of deficiency is xerophthalmia, an eye condition which results in difficulty seeing in low light environments.

Also known as:  3-Dehydroretinol, 3-Déhydrorétinol, Acétate de Rétinol, Antixerophthalmic Vitamin, Axerophtholum, Dehydroretinol, Déhydrorétinol, Fat-Soluble Vitamin, Oleovitamin A, Palmitate de Rétinol, Retinoids, Rétinoïdes, Retinol, Rétinol, Retinol Acetate, Retinol Palmitate, Retinyl Acetate, Rétinyl Acétate, Retinyl Palmitate, Rétinyl Palmitate, Vitamin A Acetate, Vitamin A Palmitate, Vitamin A1, Vitamin A2, Vitamina A, Vitamine A, Vitamine A1, Vitamine A2, Vitamine Liposoluble, Vitaminum A

Diseases and Conditions

Vitamin A is likely effective for treating vitamin A deficiency. Vitamin A is possibly effective for the following conditions:

  • Breast cancer
  • Cataracts
  • HIV-related diarrhea
  • Malaria
  • Measles
  • Oral leukoplakia
  • Photoreactive keratectomy
  • Post-partum complications
  • Pregnancy-related complications
  • Retinitis pigmentosa

Vitamin A is possibly ineffective for the following conditions:

  • Bronchopulmonary dysplasia
  • Chemotherapy-induced gastrointestinal adverse effects
  • Fetal and early infant mortality
  • Melanoma
  • Miscarriage
  • Osteoarthritis
  • Tuberculosis
  • Head and neck cancers
  • HIV transmission
  • Lower respiratory tract infections
  • Pnuemonia.

There is insufficient information on the effectiveness of vitamin A for the following conditions:

  • Alcohol-related liver disease
  • Anemia
  • Cervical cancer
  • Child development
  • Chronic myelogenous leukemia
  • Chronic radiation proctitis
  • Colorectal cancer
  • Esophageal cancer
  • Gastric cancer
  • HIV
  • Lung cancer
  • Ovarian cancer
  • Pancreatic cancer
  • Prostate cancer
  • Overall mortality

Safety

Vitamin A is likely safe when used orally, intramuscularly, and appropriately within the tolerable upper intake level of vitamin A (10,000 units per day for adults). Doses at higher ranges may increase the risk of adverse side effects. Prolonged use of high doses can cause significant adverse effects such as hypervitaminosis A. Vitamin A is likely safe for children to take orally under the supervision of a physician. It is likely safe for pregnant and breastfeeding women to orally take vitamin A under the supervision of a physician. Vitamin A is generally safe when consumed within the recommended daily allowance (RDA), but the benefits of vitamin A supplements is controversial since studies show no health benefits nor adverse effects. Despite this, high doses of vitamin A is not encouraged. Possible side effects may include:

  • Hypotension
  • Reversible hypothyroidism
  • Dry mouth
  • Cheilitis
  • Dry mucosae
  • Bleeding
  • Steatosis
  • Perisinusoidal fibrosis
  • Chronic hepatitis
  • Cirrhosis
  • Sepsis
  • Depression
  • Suicidal ideation
  • Conjunctivitis
  • Coughs and fever in children

Medication Interactions

Vitamin A may interfere with hepatotoxic drugs such as:

  • Cetaminophen (Tylenol)
  • Amiodarone (Cordarone)
  • Carbamazepine (Tegretol)
  • Isoniazid (INH)
  • Methotrexate (Rheumatrex)
  • Methyldopa (Aldomet)
  • Retinoids such as acitretin (Soriatane)
  • Bexarotene (Targretin)
  • Etretinate (Tegison)
  • Isotretinoin (Accutane)
  • Tretinoin (Retin-A, Renova)
  • Tazarotene (Avage)
  • Tetracycline antibiotics such as demeclocycline (Declomycin), minocycline (Minocin), and tetracycline (Achromycin), and warfarin (Coumadin)

Supplement and Food Interactions

Vitamin A may negatively interact with iron supplements. 

Dosage

The recommended intake for vitamin A for people aged 14 years and older ranges between 700 and 900 micrograms (mcg) of retinol activity equivalents (RAE) per day. The recommended intake for women who are nursing ranges between 1,200 and 1,300 RAE. Lower values are recommended for infants and children younger than 14.

Foods

Foods which contain vitamin A include:

  • Liver
  • Kidney
  • Eggs
  • Dairy
  • Dark or yellow vegetables
  • Carrots
  • Tree nuts.

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References

  1. https://ods.od.nih.gov/factsheets/VitaminA-Consumer/
  2. http://www.umm.edu/health/medical/altmed/supplement/vitamin-a-retinol
  3. https://naturalmedicines.therapeuticresearch.com/databases/food,-herbs-supplements/professional.aspx?productid=964

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