Vitamin A (Retinol)

Vitamin A is a fat-soluble vitamin that provides a number of important functions in the body. Vitamin A plays vital role in the following:

  • Normal cell reproduction.

  • Vision.

  • Pattern formation during embryogenesis. Vitamin A is required for health growth and development of the embryo and fetus. Vitamin A influences gene development and helps to determine the sequential development of the fetus's organs during different growth stages.

  • Proper development. Vitamin A is required for proper bone development, hematopoiesis and brain development.

  • Proper immune function. Maintains proper functioning of the immune system

  • It is also believed that Vitamin A may play an important role in the development and function of certain aspects of male and female reproductive system.

While vitamin A deficiency is harmful to anyone, children appear to be most susceptible to the effects of vitamin A deficiency. While vitamin A deficiency is not common in the United States, deficiency is a serious public health issue in many developing and third world countries.

Vitamin A deficiency usually occurs under specific conditions. These include inadequate dietary intake of vitamin A or provitamin A, malabsorption syndromes (cystic fibrosis, Whipple's disease, Crohn's disease, ulcerative colitis, and short bowel syndrome), pancreatic disease, and chronic liver disease (e.g., cirrhosis).

Liver, fish liver oils (e.g., cod liver oil), egg yolks, butter, and cream are all rich sources of vitamin A.

Suggested Benefits of Vitamin A Supplementation

For those with Vitamin A deficiency, supplemental Vitamin A may help when used in connection with the following conditions:
  • Anemia
  • Childhood diseases
  • Cystice fibrosis
  • Infection
  • Leukoplakia
  • Measles
  • Night blindness
Vitamin A Dosage Recommendations

The two primary forms of vitamin A are retinyl acetate and retinyl palmitate. Multivitamin preparations almost always contain vitamin A as a combination of vitamin A and beta-carotene (provitamin A) or beta-carotene alone. Doses higher than 5,000 IU of vitamin A are rarely exceeded in these preparations. Any dose of supplemental vitamin A greater than 10,000 IU daily is not recommended. Many take beta-carotene for vitamin A supplementation. Cod liver oil (and other fish oils) supplements are a great source of supplemental Vitamin A.

Precautions

High intakes of vitamin A may cause acute or chronic toxicity. Taking too much Vitamin A higher than recommended doses of Vitamin A is not advisable.

Supporting Literature

Barber T, Borrás E, Torres L, et al. Vitamin A deficiency causes oxidative damage to liver mitochondria. Free Rad Biol Med. 2000; 29:1-7.
Humphrey JH, Rice AL. Vitamin A supplementation of young infants. Lancet. 2000; 356:422-424.
Biesalski HK. Comparative assessment of the toxicology of vitamin A and retinoids in man. Toxicology 1989;57:117-161.
Benn CS, Aaby P, Balé C, et al. Randomized trial of effect of vitamin A supplementation on antibody response to measles vaccine in Guinea-Bissau, West Africa. Lancet. 1997; 350:101-105.
Bendich A, Langseth L. Safety of vitamin A. Am J Clinical Nutrition 1989;49:358-370.
Ross AC, Stephensen CB. Vitamin A and retinoids in antiviral responses. FASEB J. 1996; 10:979-983.
Wolf G. Vitamin A functions in the regulation of the dopaminergic system in the brain and pituitary gland. Nutritional Review. 1998; 56:354-358.

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