Cosmeceutical Critique: Vitamin A, Retinol and RetinoidsDr. Leslie Baumann
Volume 32, Issue 5, Page 25 (May 2001)
Vitamin A and its derivatives are very popular ingredients in cosmeceutical products. All of the natural and synthetic derivatives of vitamin A are included in a group known as the retinoids.
The retinoids have many important biologic effects: They regulate growth and differentiation of epithelial cells, inhibit tumor promotion during experimental carcinogenesis, diminish malignant cell growth, decrease inflammation and enhance the immune system (J. Am. Acad. Dermatol. 39[4, pt. 1]:611-25, 1998).
Retinoic acid, or tretinoin, is now known to reverse photoaging by reducing wrinkles and smoothing skin texture as well as decreasing actinic keratoses and lentigines (Dermatol. Clin. 18:699-709, 2000).
Retinoids have also been shown to improve the appearance of striae and improve skin discoloration (J. Am. Acad. Dermatol. 39 [2, pt. 3]:S1-122, 1998).
Long-term studies have shown that the visible skin changes found with tretinoin use result primarily from an increase in dermal collagen, a decrease in abnormal elastin, increased dermal and epidermal mucin, an improved dermal-epidermal junction, and decreased melanin (Dermatol. Clin. 18:99-112, 2000).
Tretinoin also decreases the transcription factor AP-1, leading to reduced levels of collagenase and other metalloproteinases (N. Engl. J. Med. 337:1419-28, 1997).
Tretinoin, however, is available by prescription only. It has two approved uses: treating acne and improving photodamaged skin.
Because tretinoin is expensive and usually not covered by prescription drug insurance, many patients are interested in using over-the-counter products that contain retinoids. Most such products contain either retinyl palmitate or retinol.
Retinyl palmitate has not been found to be biologically active in the skin (J. Am. Acad. Dermatol. 39[2, pt. 3]:S2-7,1998). To be converted to retinol, retinyl palmitate requires cutaneous cleavage of its ester bond and then conversion to retinoic acid in order to exert an activity when applied topically. Many products that claim to contain retinol actually contain retinyl palmitate.
Retinol, on the other hand, is highly useful in skin care. Retinol is a pro-drug that can be converted to retinoic acid by the skin. The change to all-trans retinoic acid within the keratinocytes is essential for retinol to be active (J. Biol. Chem. 269:32821-27, 1994).
Early reviews of retinol found it to be ineffective; however, further research determined that this was due to the molecule's photoinstability. Upon exposure to light, retinol degrades into a biologically inactive molecule. This breakdown can be prevented by adding an antioxidant or by incorporating retinol into an oxidation-resistant vehicle.
Recent investigations of retinol in an appropriate vehicle and in the correct concentration have shown it to be as effective as tretinoin for the same indications.
In one study, unoccluded retinol at 0.25% was found to induce the same cellular and molecular changes observed with the application of 0.025% tretinoin—without the irritation usually seen with tretinoin. In addition, the investigators found that retinol penetrated the skin better than tretinoin (J. Invest. Dermatol. 109:301-05, 1997).
Side effects have been found to be fewer than those seen with tretinoin; therefore, retinol may be an excellent alternative for patients with sensitive skin. In addition, vitamin A is also known to be a humectant moisturizer and therefore is a useful additive in products meant to moisturize the skin (Dermatol. Clin. 18:597-607, 2000).
While prescription-strength retinoids are known to be successful in reversing and preventing the signs of aging, it is important to remember that properly formulated retinol products can be efficacious as well. These products must be packaged in special low-light conditions to ensure stability. They should be packaged in lightproof aluminum tubes. Most over- the-counter products contain 0.04%-0.08% retinol.
It is impossible to ascertain by reading the label which products are manufactured and packaged properly, so it is best to stick with reputable brands that you can trust.
In order to better guide our patients, we went to a local pharmacy and purchased every product containing or claiming to contain retinol. For each, we examined the packaging and the product inside as well as any labeling or marketing from the company.
Two examples of brands that are manufactured and packaged properly are RoC Retinol Actif Pur and Neutrogena Healthy Skin. I feel comfortable recommending these to my patients.
Advise your patients to use retinol products at night, when degradation by light is minimal. Some products are marketed with added sunscreens for daytime use. It is very important for patients on retinoids of any kind to apply sunscreen daily, as retinoid use is associated with increased photosensitivity.
DR. LESLIE BAUMANN is director of cosmetic dermatology at the University of Miami. Melissa Lazarus, a research fellow at the university, contributed to the column. To respond to this column, write to Dr. Baumann at our editorial offices.
© 2001 International Medical News Group. Published by Elsevier Inc. All rights reserved.