vitamin A

vitamin A An oil-soluble vitamin that is also known as retinol. Carotene compounds are gradually converted by the body to vitamin A. A form of vitamin A called retinal is responsible for transmitting light sensations in the retina of the eye. Vitamin A is found in egg yolk, butter, cream, leafy green vegetables, yellow fruits and vegetables, cod-liver oil, and similar fishliver oils. Deficiency of vitamin A leads to night blindness and to diseases that affect the eyes and mucous membranes. Overdose of vitamin A can cause insomnia, joint pain, fatigue, irritability, headache, and other symptoms. The daily adult requirement is 900 micrograms.