Read More Vitamin A
Vitamin A Facts
Vitamin A is essential for immune function, vision, reproduction, and cellular communication. Vitamin A is critical for vision as a basic component of rhodopsin, a protein that absorbs light in the retinal receptors. This compound encourages cell growth and differentiation. It plays a crucial role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs.
Preformed vitamin A (retinol, retinal, and retinoid) are found in foods of animal origin such as egg yolk, liver, fish, butter, and cheese. These forms of vitamin A are ready to be used by the body, directly from the food. Provitamin A is found in plant sources. It is estimated that 30% of available provitamin A is found in carrots, with leafy greens and sweet potatoes also acting as significant sources. These sources are converted to vitamin A in the body. The RDA for adults is: 900 micrograms daily (3,000 IU) for men and 700 micrograms daily (2,300 IU) for women
Vitamin A deficiency is rare in the United States, but is common in developing countries. Preterm infants and people with cystic fibrosis commonly have vitamin A deficiencies. Research indicates that those with cancer, age-related macular degeneration and measles may benefit from vitamin A supplementation.