Anti-aging products include Vitamin A derivatives,
or retinoids, to restore a youthful complexion.
Photo credit: Joyce E.M. Wall
Vitamin A is a fat-soluble vitamin that it is absorbed through the intestinal tract (with the help of lipids) and accumulates in the liver and fatty tissues. It is needed by the retina of the eye in the form of a light-absorbing molecule called retinal, which is necessary for normal vision. When Vitamin A is irreversibly oxidized to retinoic acid, it functions as an important hormone-like growth factor for epithelial and other cells. Vitamin A and its derivatives maintain the structural and functional integrity of eyes, bones, membranes, the immune system and the skin.
Vitamin A Science [1][2]
Vitamin A from animal food sources, such as liver and milk, is known as preformed vitamin A and is an ester called retinyl palmitate. It is absorbed in the form of retinol, which is one of the most usable or active forms of the vitamin. Vitamin A from colorful fruits and vegetables is called provitamin A carotenoid. Common forms are beta-carotene, alpha-carotene, and beta-cryptoxanthin (all are converted into vitamin A, but beta-carotene is the most efficiently converted). They can be made into retinol in the body. Retinol can be made into retinal (the visually active aldehyde form, retinaldehyde) and retinoic acid (a.k.a. tretinoin), which has only partial vitamin A activity and does not function in the retina; it functions in embryological development, the growth and development of bone, and the maintenance of skin.
Retinol and retinyl palmitate, two forms of vitamin A, are among the most widely used active ingredients in skin care products. Vitamin A does not have much of a direct biological effect; it works via its active metabolite (biochemical derivative), retinoic acid. Only retinoic acid and its analogs (collectively called retinoids) have direct effects on skin cells and can adjust their physiology toward a more youthful state. Retinoic acid, or tretinoin, is the active ingredient in anti-wrinkle creams such as Retin A Micro and Renova.
Skin cells have specialized enzymes that convert various forms of vitamin A into retinoic acid. If sufficient amounts of retinyl palmitate, retinaldehyde, or retinol are added to a culture of skin cells, the concentration of retinoic acid in the cells increases. So the idea is that vitamin A may deliver at least some of the benefits of retinoic acid to the skin thereby encouraging its renewal and youthful appearance. Some forms of vitamin A are more easily converted to retinoic acid than others. The conversion pathway proceeds in corresponding metabolic steps to convert retinol and retinyl palmitate to retinoic acid. The overall rate of conversion of retinol to retinoic acid is low and that of retinyl palmitate is even lower. So a relatively large concentration of retinol and an even larger amount of retinyl palmitate needs to be delivered into a cell to boost retinoic acid levels and produce clinically meaningful effects.
Retinyl palmitate <=> Retinol <=> Retinaldehyde => Retinoic acid (Tretinoin)
Vitamin A and Skin [3][4]
There is a substantial focus on anti-aging products and many cosmeceuticals contain vitamin A derivatives, which can be highly effective in improving skin and restoring its youthfulness. Wrinkling, acne, discoloration, milia, and other anomalies can be managed with vitamin A treatment. Two products with established powerful effects on skin include Green Cream (available over the counter) and Retin A Micro (available only by prescription).
Green Cream is a high potency retinol product that was developed by a U.S. dermatologist in the 1980's (the color of the formula was a random choice but patients kept referring to it as green cream and so the product was branded). Advanced Skin Technology (AST) has licensed this patented technology and formulated three levels (3, 6, and 9) of this cream for the topical treatment of skin. Ingredients include retinol at various concentrations in all 3 levels. The transport vehicle for retinol delivery into the skin is an aloe gel-based polymer, which accomplishes the following:
• Exfoliation of the skin resulting in a radiant glow.
• Minimization of scars, pores, wrinkles, and fine lines.
• Smoothing of skin tone and texture.
• Getting rid of blemishes.
Retin-A Micro (tretinoin gel), is a formulation for the topical treatment of acne that uses microsphere technology in an aqueous gel to deliver tretinoin to the skin. Ingredients include tretinoin at 0.1% and 0.04% in either of two levels. It works at the molecular level as it binds to retinoid receptors that regulate gene expression. The result is stimulation of mitotic activity and a turnover of skin cells leading to eradication of inflammation and acne, diminishment of fine lines and wrinkles and, ultimately, clear skin.
Vitamin A can be obtained through food sources and in supplemental form (RDA for Vitamin A for the average adult is 2,310IU (female) – 3,000IU (male)). It is an important cofactor or helper molecule that assists in important biochemical transformations in the body that maintain vision, bone growth, reproduction, cell division, the immune system, white blood cell formation, the healthy surface linings of eyes and respiratory, urinary, and intestinal tracts, and it helps the skin and mucous membranes function as a barrier to bacteria and viruses. It is highly effective in maintaining skin health and is often used in cosmeceuticals in anti-aging and acne treatments. There are thousands of documented testimonials from end users of retinol based products that validate their skin enhancing effects. It has been well established in the scientific community that the retinoid family of compounds is highly effective at managing skin issues that include wrinkles, fine lines, discoloration, and acne. When used appropriately, products containing effective concentrations of vitamin A derivatives result in anti-aging effects that help the skin maintain a youthful appearance.
Reference links:
1. http://www.smartskincare.com
2. http://ods.od.nih.gov/factsheets/vitamina.asp
3. http://www.advancedskintech.com/greencream.htm
4. http://www.retinamicro.com/hcp
Copyright ©2010 Joyce E.M. Wall
Comments
Beta-carotene is provitamin form of vitamin A. It consist of two molecules of retinaldehye linked at their aldehyde end. Beta-carotene(provitamin A) is hydrolyze to retinal in the lumen of the intestine by beta-carotene dioxygenase. Retinal is reduced to retinol by retinaldehyde reductase,an NADPH-requiring enzyme within the intestines.
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