Scientifically Advanced Skin CareJanuary 2007
By Dave Tuttle
Green Tea Polyphenols: Powerful Antioxidant Protection
Green tea is one of the world’s most popular beverages, particularly in Asian countries like China, Korea, Japan, and India. Green tea is valued for its many contributions to whole-body health, and emerging research demonstrates that green tea benefits the skin as well as the rest of the body.
Green tea leaves contain polyphenols that are recognized as potent antioxidants and effective scavengers of free radicals. These include a variety of catechins, the most important of which is epigallocatechin-3-gallate (EGCG).26
Numerous studies have shown that topical application of green tea confers broad-spectrum protection against photodamage, one of the leading causes of visibly aged skin. Polyphenols from green tea leaves have been found to protect against the adverse effects of overexposure to ultraviolet light.
For example, in a study at Case Western Reserve University, volunteers had areas of their skin treated with a green tea extract.27 Thirty minutes later, they were exposed to simulated solar radiation at a dose high enough to produce inflammatory redness, or erythema. The portions of the skin treated with green tea extracts had a reduced number of sunburn cells, and immune cells just below the skin surface were protected from the effects of the radiation. Green tea extract also protected against radiation-induced DNA damage. The researchers concluded that green tea polyphenols are effective in averting many of the detrimental effects of sunlight, and may thus serve as natural photoprotective agents.27 The photoprotective benefits of topical green tea have also been reported in other studies as well.28-30
A study from Korea found that when EGCG is topically applied to aged human skin, it stimulates the proliferation of epidermal keratinocytes, which increased the thickness of the epidermis.26 EGCG also inhibited the death of the keratinocytes after a period of exposure to ultraviolet radiation, thus conferring important photoprotection.
When topically applied or consumed orally, green tea polyphenols enhance cells’ protective responses to inflammation and various chemicals that promote tumor growth. At the same time, these phytochemicals prevent ultraviolet B-induced oxidative stress and immune system suppression.31
By countering the effects of ultraviolet light and other cancer-inducing agents, green tea provides crucial protection to delicate skin tissues.
Glycolic, Hyaluronic Acids Aid Skin Texture, Appearance
As people grow older, they often notice that their skin becomes dry and discolored. Glycolic acid and hyaluronic acid may help to alleviate these signs of skin aging.
Derived from sugar cane, glycolic acid is considered the most powerful of the skin-rejuvenating fruit acids called alpha-hydroxy acids. Glycolic acids helps trap moisture in the skin, promote collagen formation, and release the buildup of dead skin cells to reveal brighter, younger-looking skin. Widely used as an anti-aging agent for the skin, glycolic acid has demonstrated its efficacy in numerous studies.
In a three-month study, people who applied topical glycolic acid to the face and neck demonstrated improvements in all assessments of photoaging, including statistically significant gains in general skin texture, color, and wrinkle reduction.32 A six-month study with 65 particiants noted an average 27% increase in epidermal thickness in those who used a daily topical glycolic acid cream.33
A study at Yale Medical School also found that applying a glycolic acid cream before exposure to ultraviolet B light helped protect the skin against inflammation and redness (erythema) from sunburn. Daily application of glycolic acid for seven days after sun exposure reduced redness and inflammation by 16%.34 This effect suggests that glycolic acid confers antioxidant effects in the skin.
Another important and innovative ingredient in skin care is hyaluronic acid. A large sugar-like molecule found in every tissue of the body, hyaluronic acid is particularly important to the skin’s extracellular matrix, where it attracts and binds with water and its gel-like structure provides volume and fullness for the skin. Hyaluronic acid is thus crucial for maintaining smoothness and moisture in the skin.35
Hyaluronic acid also stimulates wound healing and helps protect wounds from free-radical damage. A study at the Wound Healing Center in Brescia, Italy, revealed that topically administered hyaluronic acid permeates the skin and provides powerful antioxidant protection against free radicals.36 This bolsters the skin’s ability to heal from cuts and abrasions.
Glycolic and hyaluronic acids thus provide crucial antioxidant protection to the skin, restoring healthy texture, color, and moisture content.
Vitamins C and E Defend Against Free Radicals
Since the skin can easily be overwhelmed by free-radical-induced oxidative stress, ensuring broad-spectrum antioxidant protection is crucial in fighting skin aging. Decades of research have shown that vitamin E and vitamin C are especially important in preserving and restoring skin health.
Vitamin E is the primary naturally occurring antioxidant in the stratum corneum, the outermost layer of the epidermis. Composed primarily of alpha-tocopherol, this vitamin provides the bulk of our first-line defense against free radicals.37 As a result, tocopherol depletion is a very early and sensitive biomarker of environmentally induced oxidative stress. Under such conditions, topical application of antioxidants can support the physiological mechanisms that maintain or restore a healthy skin surface.38
An experiment at the University of California, Berkeley, found that ultraviolet radiation significantly decreases concentrations of vitamin E in the skin.39 However, when vitamin E-rich oil was applied before the skin was subjected to radiation, much higher concentrations of vitamin E were preserved. This suggests that topical use of vitamin E can help maximize its concentration in the skin, helping to fight free radicals generated by solar radiation and other environmental stressors.
In a double-blind study, a topical vitamin C complex was applied to one half of the face and a placebo gel to the opposite side. Clinical evaluation of wrinkling, pigmentation, inflammation, and hydration was performed prior to the study and at weeks 4, 8, and 12. The results showed a statistically significant improvement of the vitamin C-treated side, with decreased photoaging scores of the cheeks and the peri-oral area. The overall facial improvement of the vitamin C side was statistically significant. Biopsies showed increased collagen formation in the vitamin C group. This study demonstrated that topically applied vitamin C results in clinically visible and statistically significant improvement in wrinkling when used for 12 weeks. This clinical improvement correlated with biopsy evidence of new collagen formation.40
A randomized, double-blind, controlled study was conducted on human volunteers to determine the efficacy of topical vitamin C application in treating mild-to-moderate photodamage of facial skin. Methods of evaluating efficacy included an objective, computer-assisted image analysis of the skin surface, subjective clinical photographic analysis, and a patient self-appraisal questionnaire. Topical vitamin C was applied to one side of each patient’s face and a control vehicle on the other side for three months.41
The results using the optical image analysis demonstrated that compared to the placebo vehicle, the vitamin C-treated side of the face showed a statistically significant 71% combined score improvement. Clinical assessment parameters demonstrated significant improvement with vitamin C treatment compared to the placebo vehicle for fine wrinkling, tactile roughness, skin laxity/tone, sallowness/yellowing, and overall features. Patient questionnaire results demonstrated statistically significant improvement overall with the vitamin C treatment (84% greater than control). Photographic assessment demonstrated significant improvement with vitamin C treatment (58% greater than control). This three-month study using topical vitamin C provided objective and subjective improvements in photodamaged facial skin.41
A study of vitamins C and E in young, aged, and photodamaged human skin sought to ascertain the various levels of these antioxidants in each skin type. The findings showed that the concentration of vitamin E was significantly lower in the epidermis (upper layer) of photoaged skin (56% lower than in young skin) and aged skin (61% lower than in young skin). There was no difference in vitamin E levels in the dermis of each skin type. In photoaged skin, vitamin C levels were 69% lower in the epidermis and 63% lower in the dermis; in naturally aged skin, vitamin C levels were 61% lower in the epidermis and 70% lower in the dermis. Glutathione concentrations were also lower compared to young skin. These results show that the antioxidant defense systems in normal aged and photoaged human skin are significantly diminished compared to young skin.42
Vitamin E and vitamin C thus work together to provide antioxidant protection, support collagen synthesis, and reduce wrinkling of the skin.
The skin’s complex structure is vulnerable to free-radical-induced stress that manifests over time as wrinkles, dryness, thinning, and discoloration. Fortunately, innovative topical skin care agents help fight the signs of photoaging while restoring moisture, minimizing wrinkles, and improving the overall texture, health, and appearance of the skin.
Diligent daily use of topical nutritional and botanical agents such as Matrixyl™ 3000, ceramides, glycolic acid, hyaluronic acid, idebenone, pomegranate, green tea, and vitamins E and C can help preserve and enhance skin quality. Advanced topical skin care should thus be considered an important component of a comprehensive anti-aging strategy, with the added benefit of producing highly visible results in a matter of only weeks or months.
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