Introduction
The substances collagen and elastin give skin its firmness and elasticity.
With age, though, the collagen and elastin content of the skin gradually
decreases. As a result, the skin becomes looser, weaker, less elastic, and drier.
In addition, the fat pads under the skin begin to disappear. Wrinkles form, and
the skin begins to sag.
This gradual loss of structure has several causes: genetic programming (a built-in
“clock” that causes aging), cumulative sun damage (photoaging), and direct
chemical effects from cigarette smoking or abrasive chemicals, or both. Sun damage
also causes fine wrinkles that disappear when stretching the skin, surface
roughness, mottled pigmentation, “liver” spots, and skin
cancer.
In people who already have signs of aging skin and wish to reverse it, a number of
treatments are available. The drug tretinoin (retinoic acid, or Retin-A), a
substance related to vitamin A, has been shown effective for reversing the fine
wrinkles, splotchy pigmentation, and rough skin of sun damage. The hormone
estrogen is thought to help restore normal skin tone in
menopausal women, but the evidence for this widely held belief remains weak.
More aggressive treatments for aging skin include injections of botulin toxin,
dermabrasion, chemical peels, soft tissue augmentation, laser resurfacing, and
Gore-Tex threads.
Principal Proposed Natural Treatments
Two classes of natural treatments have shown promise in the treatment of aging skin: alpha-hydroxy acids (AHAs) and antioxidants. However, the evidence that they work remains incomplete, and AHAs can cause significant side effects.
Alpha-hydroxy acids. Alpha-hydroxy acids, such as glycolic acid
and lactic
acid, are substances derived from fruit and dairy products.
These are milder relatives of the substances used by dermatologists in chemical
peels, which are designed to remove damaged layers of the skin. Cosmetics
manufacturers are now adding AHAs to many skin-care products.
Meaningful evidence in support of AHAs comes from one double-blind, placebo-controlled study reported in 1996. This twenty-two-week study enrolled seventy-four women with sun-damaged skin. Participants received either 8 percent glycolic acid, 8 percent L-lactic acid, or placebo cream and applied it to the face and forearm. Although participants showed improvements in each of the three groups, superior results were achieved with each of the AHA creams than with the placebo cream. Another double-blind study compared estrogen cream, glycolic acid cream, and their combination with placebo. Both estrogen and glycolic acid improved skin aging.
AHAs are not always harmless. Possible side effects include burning, blistering,
severe redness, swelling (especially in the area of the eyes), bleeding, rash, and
increased sensitivity to the sun. There are also concerns that AHAs may increase
the risk of skin cancer. For all these reasons, the U.S. Food and Drug
Administration continues to investigate the use of AHAs in
cosmetic products to determine whether they should be reclassified as drugs.
Antioxidants. The ultraviolet light from the sun creates
free
radicals, naturally occurring substances that can harm many
tissues of the body, including the skin. Antioxidants
are substances that neutralize free radicals. On this basis, various antioxidants
have been investigated for their potential usefulness in treating or preventing
photoaging.
A small, three-month, double-blind, placebo-controlled study found benefit with a cream containing 5 percent alpha-lipoic acid. The use of this antioxidant substance improved several measures of aging skin especially skin roughness, compared with placebo. Benefits have also been seen in preliminary studies with a cream containing vitamin C. In a small double-blind study, the use of mixed antioxidants (lycopene, beta-carotene, vitamin E, and selenium) for twelve weeks improved skin roughness and scaling.
Oligomeric
proanthocyanidin complexes (OPCs) made from grape seed or
pine bark are widely marketed for the treatment of aging skin. These substances,
closely related to bioflavonoids, have antioxidant properties and might also
protect and strengthen collagen and elastin. These effects provide theoretical
reasons to believe that OPCs might be helpful for the treatment of aging skin.
However, despite widespread marketing, no properly designed studies have been
reported to indicate that OPCs provide any benefit.
In an eight-week, double-blind, placebo-controlled study of forty women who already had sun-damaged skin, the combined use of oral green tea and a topical green tea cream failed to prove more effective than placebo in improving the condition of sun-damaged skin. Some possible benefits were seen in microscopic evaluation of skin condition.
Studies on laboratory animals found that topical vitamin C and vitamin E helped prevent burning on exposure to ultraviolet light. A small double-blind study found that 2 grams (g) of vitamin C and 1,000 international units (IU) of vitamin E taken orally for eight days resulted in a modest decrease of sunburn induced by ultraviolet light. In addition, a fifty-day, placebo-controlled study of forty people found that higher doses of these vitamins provided a sun protection factor (SPF) of about 2.16. (The sun protection factor is 15 or higher in many sunscreens.) It appears that these vitamins must be taken together for best effect; when used alone, they do not appear to work.
The oral use of beta-carotene, lycopene, and other carotenoids
has shown preventive effects in some studies. Benefits have also been seen with
mixtures of various antioxidants taken together (vitamin E, zeoxanthin, lutein,
beta-carotene, and others).
Oral vitamin A has shown some promise for preventing skin cancer in people at risk for it, but the doses used in studies were quite high, considerably above recommendations for the maximum safe dose. Vitamin A should not be used with the drug tretinoin.
Topical vitamin A may be helpful for treatment of aging skin. One double-blind, placebo-controlled study found that a 0.4 percent vitamin A lotion applied three times a week significantly reduced the number of “fine” wrinkles in seniors. Benefits were also seen in terms of some biochemical measures of skin health.
Because these antioxidants work in an entirely different manner from standard sunscreen, it is reasonable to believe that they could offer a synergistic effect if taken while using sunscreen. However, this hypothesis has not been studied.
Other substances with antioxidant actions that have shown some promise for treating or preventing aging skin include cocoa, Vitis vinifera extract, milk thistle, and zinc. However, the supporting evidence that the use of these substances (taken either orally or topically) offers any benefit for the skin remains far too preliminary to be relied upon.
Any discussion of the potential benefits of antioxidants for preventing cancer must include the startling finding of a large study that tested the effect of mixed antioxidants. This trial, enrolling 7,876 women and 5,141 men, evaluated the potential benefits of a combination of vitamin C, vitamin E, beta-carotene, selenium, and zinc for preventing cancer. According to results published in 2007, no benefits were seen among the male participants, but among women, skin cancer rates actually appeared to increase. The cause of these findings remains unclear.
Other Proposed Natural Treatments
In a double-blind study of fifty women with signs of aging skin, the use of
topical niacinamide cream significantly improved skin appearance and elasticity
compared with placebo cream. A study published in 2007 tested a purified soy
isoflavone product (technically, isoflavone aglycones) for
treatment of aging skin. In this double-blind trial, twenty-six Japanese women in
their late thirties and early forties were given either placebo or 40 milligrams
(mg) daily of soy isoflavone aglycones for twelve weeks. Researchers monitored two
types of wrinkles near the eye: “fine” wrinkles and “linear” wrinkles. The results
indicated that the use of the soy product significantly reduced fine wrinkles
compared with placebo. (Effects on linear wrinkles were not significant.) As a
secondary measure, researchers also analyzed skin elasticity and found an
improvement in the women given the isoflavones compared to those given
placebo.
An unusual soy extract containing soybean trypsin inhibitor and Bowman-Birk protease inhibitor has also shown promise for aging skin. Sixty-five women with moderate skin damage from the sun received either soybean extract or placebo cream for twelve weeks. Compared to the women in the placebo group, treated women showed an improvement in mottled pigmentation, blotchiness, dullness, and fine lines, and an overall enhancement of texture, skin tone, and appearance.
The substance glucosamine is widely used for osteoarthritis, in part
because it seems to help collagen regenerate. For this reason, it has been
advocated as a treatment for aging skin. However, the only evidence that it works
comes from one poorly designed study. In this single-blind trial, seventy-two
women with symptoms of aging skin were divided into two unequal groups: a small
group that received no treatment and a much larger one that received a proprietary
mixture of glucosamine, amino acids, and minerals. The results indicated greater
improvement in the treated group compared to the untreated group. However, because
this was not a double-blind, placebo-controlled study, the results cannot be taken
as reliable.
The mineral silicon also has been proposed as a treatment for aging skin. In the one potentially meaningful published study, fifty women with sun-damaged skin were given either 10 mg silicon daily (as orthosilicic acid) or placebo for twenty weeks. Measurements of skin roughness and elasticity showed improvement in the silicon group compared with the placebo group. However, this study, performed by the manufacturer of a silicon product, was not well designed or well reported.
A proprietary dietary supplement containing soy, fish protein polysaccharides, white tea extract, and many other ingredients has also shown promise, according to a study performed by the manufacturer. Another study provides weak evidence that the substance DHEA (dehydroepiandrosterone) might be helpful for improving skin condition in the elderly.
In a preliminary double-blind study, coriander oil applied topically was more effective than a placebo cream at reducing redness from UVB exposure. This effect may or may not translate into long-term benefit for aging sun-damaged skin.
Numerous herbs and other natural products have been advocated for the treatment of aging skin. These products include aloe, Arnica, calendula, chamomile, dead sea minerals, gotu kola, para-aminobenzoic acid, thuja, and vitamin A. Other products claim to contain biological substances called growth factors (with names such as IGF-1, IGF-2, TGF-A, TGF-B, EGF, and FGF) and go on to claim that these growth factors improve skin condition. Still others claim to raise levels of human growth hormone in the body and, therefore, help produce youthful skin. However, there is no meaningful evidence that any of these treatments work.
Acupuncture face lifts are widely available for treating
facial wrinkles. They involve a series of treatments in which fine needles are
inserted into the face. However, there is no evidence to indicate that this method
produces any benefit.
Herbs and Supplements to Use with Caution
The herb St.
John’s wort contains a substance, hypericin, that increases
the skin’s sensitivity to the sun. For this reason, it is possible that the use of
St. John’s wort could accelerate sun damage of skin. Also, persons using the drug
Retin-A should not take high doses of vitamin A, as each might increase the
toxicity of the other.
Bibliography
Bissett, D. L., et al. “Niacinamide: A B Vitamin That Improves Aging Facial Skin Appearance.” Dermatological Surgery 31 (2005): 860-865.
Chiu, A. E., et al. “Double-Blinded, Placebo-Controlled Trial of Green Tea Extracts in the Clinical and Histologic Appearance of Photoaging Skin.” Dermatological Surgery 31 (2005): 855-860.
Cornacchione, S., et al. “In Vivo Skin Antioxidant Effect of a New Combination Based on a Specific Vitis vinifera Shoot Extract and a Biotechnological Extract.” Journal of Drugs in Dermatology 6 (2007): 8-13.
Elmets, C. A., et al. “Cutaneous Photoprotection from Ultraviolet Injury by Green Tea Polyphenols.” Journal of the American Academy of Dermatology 44 (2001): 425-432.
Fuchs, K. O., et al. “The Effects of an Estrogen and Glycolic Acid Cream on the Facial Skin of Postmenopausal Women.” Cutis 71 (2003): 481-488.
Greul, A. K., et al. “Photoprotection of UV-Irradiated Human Skin: An Antioxidative Combination of Vitamins E and C, Carotenoids, Selenium, and Proanthocyanidins.” Skin Pharmacology and Applied Skin Physiology 15 (2002): 307-315.
Heinrich, U., K. Neukam, et al. “Long-Term Ingestion of High Flavanol Cocoa Provides Photoprotection Against UV-Induced Erythema and Improves Skin Condition in Women.” Journal of Nutrition 136 (2006): 1565-1569.
Heinrich, U., H. Tronnier, et al. “Antioxidant Supplements Improve Parameters Related to Skin Structure in Humans.” Skin Pharmacology and Physiology 19 (2006): 224-231.
Hercberg, S., et al. “Antioxidant Supplementation Increases the Risk of Skin Cancers in Women but Not in Men.” Journal of Nutrition 137 (2007): 2098-2105.
Kafi, R., et al. “Improvement of Naturally Aged Skin with Vitamin A (Retinol).” Archives of Dermatology 143 (2007): 606-612.
Skovgaard, G. R., A. S. Jensen, and M. L. Sigler. “Effect of a Novel Dietary Supplement on Skin Aging in Post-menopausal Women.” European Journal of Clinical Nutrition 60 (2006): 1201-1206.
Wallo, W., J. Nebus, and J. J. Leyden. “Efficacy of a Soy Moisturizer in Photoaging.” Journal of Drugs in Dermatology 6 (2007): 917-922.
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