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At the proper levels, vitamin A is necessary for the human body to function. Too little or too much stresses cells and tissues and may lead to serious, life-threatening disease. A variety of symptoms occurs and the entire body is impacted.

Symptoms of Vitamin A Overdose or Deficiency

Hypervitaminosis A is the term used for the body’s response to an overdose (hypervitaminosis) of vitamin A. It results when all the binding proteins are occupied by retinoids. The condition is rare and the majority of cases results from consuming excessive animal products (especially liver), fortified foods or supplements. If the overdose is the consequence of a single excessive dose, it may be classified as acute. Chronic hypervitaminosis A results from consuming smaller excesses over a long period. Children and the elderly are most vulnerable to both types.

As hypervitaminosis A advances, it can cause eye and liver damage, osteoporosis, and disorders of the central nervous system. Certain populations show significant impact due to vitamin A overdoses. They include:

• Pregnant women. Birth defects may result if vitamin A intake is over the recommended amount during the first seven weeks of pregnancy.
  
  
• Children. Slower growth than other children in their age group is a common affect of hypervitaminosis A. The growth rate returns to normal when vitamin A intake is reduced.
  
  
• Infants. A bulging soft spot in the head may develop in infants. Additional signs and symptoms may include swelling around the optic nerve and double vision.

When additional vitamin A is necessary, physicians may recommend that patients consume more beta carotene from fruits and vegetables rather than supplements. Dietary sources are preferred because the body usually does not convert the beta carotene available in foods to retinol if sufficient vitamin A is present, avoiding the risk of an overdose. While not physically harmful, excess beta carotene is stored in fat under the skin and, in extreme cases, may cause the skin to turn yellow or orange.

Beta carotene from supplements poses health hazards that are not associated with carotenoids from food. In the body, overdoses of supplemental beta carotene may cause destruction of vitamin A and increase cell division. Most cases are associated with alcohol and cigarettes use.

In the United States, vitamin A deficiency is rare. For a healthy adult, more than a year of no intake is required for deficiency to occur. Children use the vitamin faster and have smaller stores, so deficiency can occur much faster. Deficiencies are most commonly associated with strict dietary restrictions, chronic diarrhea or alcohol abuse. They may also be related to zinc deficiency or iron deficiency, which impact the body’s ability to use vitamin A. Beginning with dry eyes and night blindness, deficiency may eventually result in total blindness or death.

Vitamin A deficiency is treated with supplements containing preformed retinol (a synthetic form) to replenish retinol stores within the body. Patients are initially given high doses of the vitamin, which are reduced over time. After several weeks, enough retinol should once again be stored in the body and supplementation may no longer be needed.