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Polarized Light Digital Image Gallery

Retinoic Acid (Vitamin A)

As a naturally occurring form of vitamin A, retinoic acid (or tretinoin) may be used topically for sun-damaged and acne-plagued skin. While the related and less effective retinol is allowed in cosmetic products, the United States Food and Drug Administration regulates retinoic acid as a prescription pharmaceutical as featured in the trade formulations Renova and Retin-A.

Retinoic acid appears to increase the rate of cell division and turnover, so when used on wrinkled, scarred, or pimply skin, damaged cells are sloughed and rapidly replaced by healthier, new epidermal tissue. As the first vitamin discovered and catalogued, thus the "A" designation, fat-soluble retinoic acid is known to increase the absorption of other chemical substances through the skin and to play a role in the embryonic development of the hindbrain and faciocranial nerves. Tretinoin may act as a signal molecule in the central nervous system, working through a nuclear receptor, and appears to influence neuron differentiation. As a possible preventative and therapeutic drug, vitamin A may modulate the immune system and control oncogenes, and is indicated to prevent breast cancer tumor growth. The essential biochemical is involved in the formation and maintenance of healthy skin, hair, and mucous membranes and is necessary for proper bone growth, tooth development, and reproduction. As the name implies (as in retina), retinoic acid helps humans see in dim light.

Dietary sources of vitamin A include cod liver oil, meats, and dairy products while plants, such as carrots, spinach, sweet potato, and mango, provide the retinoic acid precursor, carotene. Vitamin A-fortified foods including skim milk, margarine, and breakfast cereals help people meet their daily requirements. The recommended daily allowance (RDA) for vitamin A is 800 retinol equivalents per day for women and 1,000 retinol equivalents for men. Too much vitamin A can be toxic, so care is needed when supplementing a balanced diet with over-the-counter synthetics, particularly for pregnant women and nursing mothers.

Contributing Authors

Omar Alvarado, Thomas J. Fellers and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.


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