Vitamin A: Definition, Sources, Supplements & Toxicity

Vitamin A is a fat soluble vitamin that gets stored in the body for a number of functions. Vitamin A is an essential nutrient for adequate growth and development, good eye sight, proper immune response, reproduction and healthy skin. It also enhances functions of the heart, lungs, and kidneys.


There are several forms;

  • Beta carotene (Pro-vitamin ) – found mainly in plants, is an antioxidant that can be converted in the body to vitamin A.
  • Retinol (Preformed vitamin) –  an active form of  vitamin A in the blood, can be gotten from animal products. One of the richest animal sources is liver.



Food Sources

Good food sources include;




The result of either low intake in our everyday diet  or  poor absorption of the vitamin  due to an underlying  condition. It is a major health problem in children and older adults especially in Africa. 

According to World Health Organization Vitamin A deficiency (VAD) is the leading cause of preventable blindness in children and increases the risk of disease and death from severe infections. In pregnant women VAD causes night blindness and may increase the risk of maternal mortality.



Conditions affecting absorption; 

  • Zinc deficiency 
  • Chronic cigarette smoking
  • chronic alcoholism




Vitamin A is available in multivitamins and also in the form of retinyl acetate or retinyl palmitate. Younger children and adults over 71 years  are more likely to take supplements for vision, bone growth and protection against infections.

Expecting mothers need more of the vitamin for its benefits, however  excess intake during pregnancy can increase the risk of fetal abnormalities developing. According to the WHO the daily intake during any period of pregnancy should not be more than 3000μg and the weekly intake should never exceed 7500μg.




Hypervitaminosis A occur due to excess in the body. This may either be as a result of taking large amount within a short period, or gradual accumulation in the body for a very long time.

The condition may be in acute or chronic phase, with symptoms such as;

  • Headache
  • Rash
  • Hair loss
  • Itching & cracked skin
  • Nausea
  • Vomiting
  • Loss of appetite
  • Jaundice
  • Respiratory infection 
  • Abdominal pain
  • Drowsiness
  • Mood swings
  • Confusion
  • Dizziness
  • Joint pain
  • Visual disturbances
  • Cracked skin at the corners of the mouth
  • Mouth ulcers







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