Vitamin A: Retinol
Retinol is the entire vitamin A molecule, and it can be broken down into thousands of smaller components, of which one is retinoic acid (also called tretinoin, the active ingredient in Renova and Retin-A). Skin cells have a receptor site that is very accepting of retinoic acid. This relationship between retinoic acid and skin cells allows a type of communication in which the cell is told to function normally (that is, not like a damaged or older cell), and it can, to some extent, conform to that request. Retinol cannot communicate with a cell until it has been broken down into retinoic acid. Some of the controversies regarding using retinol in skin-care products have been its stability in skin or in a product, whether it can be converted into retinoic acid after it is absorbed into the skin, and how much retinol is needed so that as it is changed to retinoic acid there is still enough that can get to the cell. However, over the past couple of years, some new, stable forms of retinol have become available, along with lots of impressive research regarding their efficacy.
It now seems clears that retinol is a beneficial cell-communicating ingredient and an antioxidant. Simply put, it helps skin cells create better, healthier skin cells and increase the amount of skin-support substances. Packaging is still a key issue, so any container that lets in air (like jar packaging) or sunlight (clear containers) just won't cut it, something that applies to most state-of-the-art skin-care ingredients. Lots of retinol products come in unacceptable packaging.
One more point: Neither retinol nor retinoic acid can take care of anyone's skin-care needs on their own. For example, they don't replace the need for a well-formulated sunscreen, AHA or BHA product. AHAs and BHA have a long history of helping skin to function more normally by removing built-up layers of sun-damaged skin. Also, retinol should not be the only ingredient you look for in a moisturizer. Skin needs a combination of ingredients to function optimally, including cell-communicating ingredients (of which retinol is one), antioxidants (to reduce free-radical damage), and intercellular substances (ingredients that mimic the structure of skin). Together, all these various ingredients and elements combine to create a powerful part of any skin-care routine.
(Sources for this story: Cosmetic Dermatology, Supplement, Revisiting Retinol, January 2005, pages 1-20; Dermatologic Surgery, July 2005, pages 799-804; Plastic and Reconstructive Surgery, April 2005, pages 1156-1162; Mechanisms of Ageing Development, July 2004, 465-473; and Journal of Dermatology, November 2001, pages 595-598).