Brun, Pierre-Jacques Department of Medicine, Columbia University, New York, New York.
Blaner, William S. Department of Medicine, Columbia University, Presbyterian Hospital, New York, New York.
- Dietary sources and requirements
- Deficiency and toxicity
- Additional Readings
All-trans-retinol, an essential micronutrient that must be obtained from the diet in order to maintain good health. Vitamin A is required for maintaining vision, a healthy immune response, normal male and female reproduction, normal embryonic development, and healthy skin and barrier functions. At the cellular level, vitamin A acts essentially in vision and in regulating normal cell growth and differentiation. In vision, vitamin A serves as the visual pigment that responds directly to light. The role of vitamin A in regulating normal cell growth and differentiation involves its actions in regulating gene transcription. Both insufficient dietary vitamin A intake and excessive dietary vitamin A intake result in adverse consequences for the health of an individual. See also: Food; Malnutrition; Nutrition; Vitamin
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