The various forms of vitamin A are solubilized into micelles in the intestinal lumen and absorbed by duodenal mucosal cells. Other carotenoids in food, such as lycopene, lutein, and zeaxanthin, are not converted into vitamin A and are referred to as non-provitamin A carotenoids they might have other important activities not involving vitamin A formation. The main provitamin A carotenoids in the human diet are beta-carotene, alpha-carotene, and beta-cryptoxanthin. Provitamin A carotenoids are plant pigments that the body converts into vitamin A in the intestine. Preformed vitamin A is found in foods from animal sources, including dairy products, eggs, fish, and organ meats. The human diet contains two sources for vitamin A: preformed vitamin A (retinol and retinyl esters) and provitamin A carotenoids. Vitamin A is also critical for vision as an essential component of rhodopsin, the light-sensitive protein in the retina that responds to light entering the eye, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea. Vitamin A supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, eyes, and other organs. Vitamin A is involved in immune function, cellular communication, growth and development, and male and female reproduction. Vitamin A is the name of a group of fat-soluble retinoids, primarily retinol and retinyl esters. For a general overview of Vitamin A and Carotenoids, see our consumer fact sheet on Vitamin A and Carotenoids. This is a fact sheet intended for health professionals.

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