Update on green tea

During the last 25 years, green tea, which is derived from Camellia sinensis (an evergreen member of the Theaceae family), has gained considerable attention because of its purported antioxidant and anticarcinogenic properties. Believed to have been used by human beings for 4,000 years,¹ green tea is now one of the most heavily researched of the antioxidants, with numerous studies of its cutaneous effects appearing in the literature.² Laden with plant polyphenols, orally administered or topically applied green tea has been shown to display significant antioxidant, chemopreventive, immunomodulatory, and anti-inflammatory activity, affecting the biochemical pathways important in cell proliferation.^3-6 For this reason, and due to its global popularity as a beverage, green tea polyphenols are among the most frequently studied herbal agents used in medicine.

Polyphenols, many of which are potent antioxidants, are a large diverse family of thousands of chemical compounds present in plants. The four major polyphenolic catechins present in green tea include: ECG [(-)EpiCatechin-3-O-Gallate], GCG [(-)GalloCatechin-3-O-Gallate], EGC [(-)EpiGalloCatechin], and EGCG [(-)EpiGalloCatechin-3-O-Gallate], the most abundant and biologically active green tea constituent. In fact, EGCG is the component associated with the greatest anticarcinogenic and chemopreventive properties.⁶

A wide-ranging evidence-based review of the use of botanicals in dermatology, published in 2010, showed that the oral administration, in particular, as well as topical application of antioxidant plant extracts of green tea, among other botanicals, can protect skin against the harmful effects of UV exposure, including erythema, premature aging, and cancer.⁷

Green tea is thought to be challenging to formulate because of the inherent hydrophilicity of EGCG, which limits penetration into human skin.^8,9 Nevertheless, green tea is thought to have great potential in traditional sunscreens to enhance photoprotection.^10,11 The photoprotective activity of orally administered or topically applied green tea has been supported in various studies.^12-15

The remainder of this column will focus on recent studies of topically applied green tea polyphenols in human beings as well as clinical uses of this agent.

Topical uses

Topical green tea appears to reduce skin inflammation and neutralize free radicals, which explains its popularity as an additive in rosacea and antiaging skin care products. The antiaging effects of green tea are difficult to measure because it functions as an antioxidant that prevents aging and does not have the capacity to increase collagen synthesis or ameliorate already existing wrinkles. However, there is relatively good evidence, in comparison to other antioxidants, suggesting that topically applied green tea can help protect skin from UV radiation.¹⁶

Investigators performed a thorough literature search of all in vitro, in vivo, and controlled clinical trials involving green tea formulations and their dermatologic applications, which was published in 2012. They evaluated 20 studies, with evidence suggesting that orally administered green tea displays a broad range of healthy activity, and supportive data for the use of topically applied green tea extract for treatment of various cutaneous conditions, including acne, rosacea, atopic dermatitis, androgenetic alopecia, hirsutism, candidiasis, keloids, leishmaniasis, and genital warts.¹⁷

Also, a green tea topical formulation, green tea sinecatechin Polyphenon E ( Veregen ) ointment, has recently been shown to exert antioxidant, antiviral, and antitumor activity, and has demonstrated efficacy in treating Condylomata acuminata (external anogenital warts).¹⁸ In addition, topically applying green tea catechins in the morning in combination with traditional sunscreens is believed to have the potential to protect the skin from UV-induced damage. Topical green tea may improve rosacea, prevent retinoid dermatitis, and play a role in managing pigmentation disorders. Few of the many over-the-counter products that contain green tea catechins have been tested in controlled clinical trials and the concentration of polyphenols in these products is too low to demonstrate efficacy. It is necessary to know the amount of green tea catechins in a formulation to judge its efficacy.

Acne

In 2009, in a 6-week study investigating the efficacy of 2% green tea lotion for the treatment of mild-to-moderate acne vulgaris in 20 patients, researchers reported statistically significant reductions in mean total lesion count and mean severity index (devised by the authors to correlate with total lesion count in increasing intensity, scaled from 1 to 3). They concluded that 2% green tea lotion is both an effective and cost effective approach for treating mild-to-moderate acne lesions.¹⁹

A 2012 study revealed that ethanol extracts of several herbs, including green tea, exhibited the potential for inhibiting acne when incorporated into a topical moisturizer, specifically acting against acne-causing bacteria without provoking irritation.²⁰ Earlier that year, other investigators conducted in vitro and in vivo experiments to evaluate the effects against acne of polyphenon-60, which contains various green tea catechins (now referred to as sinecatechins in the United States.).²¹ In this clinical study, patients exhibited improvement in acne symptoms, including a reduction in the number of pustules and comedones.²²

A study published in 2013, a single-blind, placebo-controlled, split-face comparative study in 22 individuals over 60 days, evaluated the efficacy of green tea, as well as green tea plus lotus, compared with placebo for controlling casual sebum secretions in healthy adults. Compared with placebo, consistent and statistically significant decreases in sebum secretions were observed in both treatment groups. The combination of green tea and lotus extracts also achieved statistically sounder results than green tea alone. The investigators concluded that a synergistic interaction between green tea and lotus extract constituents appears to hold promise for the treatment of skin conditions in which elevated sebum levels are involved.²³

Anogenital warts

In 2006, the Food and Drug Administration approved for the first time a botanical drug formulation for the topical treatment of genital and perianal warts: sinecatechins, derived from green tea catechins and other C. sinensis constituents in a topical 15% ointment (Veregen).^{21, 24-28}

Two years later, Tatti et al. conducted a randomized, double-blind, vehicle-controlled trial to evaluate the efficacy of topical sinecatechins in 502 male and female patients (aged 18 years and older) for the treatment of anogenital warts. For 16 weeks or until complete clearance, subjects applied sinecatechins ointment 15% or 10% or vehicle (placebo) three times daily. Complete clearance was achieved in 57.2% of patients treated with 15% ointment, 56.3% using 10% ointment, and 33.7% who used only the vehicle. Respective recurrence rates, after 12 weeks, were 6.5%, 8.3%, and 8.8%. The investigators concluded that topical sinecatechins in 15% and 10% concentrations represent effective and well-tolerated options for anogenital wart treatment.²⁹

Similarly favorable results regarding polyphenon E 15% were reported in reference to three placebo-controlled clinical studies in 1,400 patients with genital warts from Europe, North and South America, and South Africa,^30,31 and by Tatti et al. again in 2010 after randomized, double-blind, vehicle-controlled safety and efficacy trials in nearly 1,000 patients treated with polyphenon E 15% and 10% formulations.²¹

Two years later, investigators evaluated sinecatechins (Polyphenon E) 10% ointment in two double-blind, multinational studies in adults with external genital and perianal warts. Polyphenon E 10% was found to be significantly more effective than vehicle in completely or partially clearing all warts.³²

Earlier that year, a review of the use of sinecatechins ointment for the treatment of external anogenital warts noted that while clearance rates are similar among sinecatechins and other indicated topical medications such as imiquimod and podophyllotoxin, recurrence rates are lower for patients treated with sinecatechins. The authors concluded that the use of sinecatechins for condylomata acuminata was safe and effective and its various molecular activities suggest broader applications to other viral and tumor lesions.³³

In 2015, Gupta and Daigle reported that sinecatechins 10% ointment for the treatment of external genital warts was found in phase III trials to display greater efficacy and lower rates of recurrence in comparison to patient-applied treatments now available.²⁸ Later that year, in a systematic PubMed and Embase review of clinical trials involving the use of polyphenol-based therapies, Tuong et al. identified cogent evidence suggesting the effectiveness of green tea polyphenols for the treatment of anogenital warts.³⁴

Antiaging activity

Green tea has been shown to work in combination with red light to exert a rejuvenating effect on the skin, as Sommer and Zhu reported in 2009 that green tea filled cotton pads applied once daily for 20 minutes prior to treatment with light-emitting diodes (central wavelength 670 nm, dermal dose 4 J/cm²) reduced wrinkles in 1 month comparably to 10 months of light treatment alone.³⁵

In 2013, Hong et al. studied the antiwrinkle effects of topically applied green tea extract with high antioxidant activity after tannase treatment. Study participants were randomly divided to receive either green tea extract or tannase-converted green tea extract on their crow’s feet for an 8-week period. The investigators found that tannase treatment elevated the antioxidant activity of green tea and imparted antiwrinkle effects.³⁶

At around the same time, Gianeti conducted clinical studies in 24 volunteers to assess the effects of a cosmetic formulation containing 6% C. sinensis glycolic leaf extracts. Skin moisture was enhanced after 30 days of topical application as was the viscoelastic-to-elastic ratio compared with vehicle and control (a forearm area left untreated). Skin roughness was significantly diminished after 30 days. The investigators concluded that the topical cosmetic formulation with green tea yielded salient moisturizing and cutaneous microrelief benefits.³⁷

Also in 2013, oral intake of green tea catechins in 16 healthy human subjects (with 14 completing the study) appeared to result in the integration of catechin metabolites into human skin linked to the negation of UV-induced 12-hydroxyeicosatetraenoic acid (12-HETE). The investigators speculated that this incorporation of catechins may render protection against sunburn inflammation and even cumulative UV-induced harm.³⁸

After earlier showing the efficacy of green tea and lotus extracts in skin disorders involving excess sebum in a single-blinded, placebo-controlled, split-face comparative study,²³ Mahmood and Akhtar conducted a 60-day placebo-controlled comparative split-face study in 33 healthy Asian men to evaluate the efficacy of two cosmetic formulations (green tea and lotus extract) for facial wrinkles. All of the formulations yielded improvements in skin roughness, scaliness, smoothness, and wrinkling, with the greatest reduction in wrinkling conferred by the combination formulation. The investigators concluded that the synergistic activity of green tea and lotus extracts exerted significant improvement along several skin parameters, suggesting the potential for these ingredients in antiaging products.³⁸

In 2014, the synergistic effects of green tea and ginkgo biloba were explored in preclinical and clinical studies. In the clinical study, 48 participants applied the formulations on forearm skin and were evaluated before and after 3 hours and following 15- and 30-day use periods. Results showed a moisturizing effect and enhancement in skin microrelief, as well as improvements in skin elasticity and barrier function.³⁹

Conclusion

Green tea remains one of the most researched antioxidants as benefits from its use continue to emerge. Indeed, green tea polyphenols are in use for a growing number of indications, especially acne and anogenital warts, and there is reason for optimism that topically applied green tea will gain momentum as an increasingly selected therapeutic option. More clinical studies are necessary to further establish the potential role of green tea for a wider range of cutaneous indications. Green tea holds particular promise in relation to photoprotection against UV-induced skin cancer and skin aging.

Dr. Baumann is chief executive officer of the Baumann Cosmetic & Research Institute in the Design District in Miami. She founded the Cosmetic Dermatology Center at the University of Miami in 1997. Dr. Baumann wrote the textbook “Cosmetic Dermatology: Principles and Practice” (New York: McGraw-Hill, 2002), and a book for consumers, “The Skin Type Solution” (New York: Bantam Dell, 2006). Her latest book, “Cosmeceuticals and Cosmetic Ingredients,” was published in November 2014. Dr. Baumann has received funding for clinical grants from Allergan, Aveeno, Avon Products, Evolus, Galderma, GlaxoSmithKline, Kythera Biopharmaceuticals, Mary Kay, Medicis Pharmaceuticals, Neutrogena, Philosophy, Topix Pharmaceuticals, and Unilever. She also developed and owns the Baumann Skin Type Solution skin typing systems and related products

References:

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3. Arch Dermatol. 2000 Aug;136(8):989-94 .

4. Photochem Photobiol. 1995 Nov;62(5):855-61 .

5. Oxid Med Cell Longev. 2012:2012:560682 .

6. J Dtsch Dermatol Ges. 2015 Aug;13(8):768-75 .

7. Am J Clin Dermatol. 2010;11(4):247-67 .

8. Dermatol Ther. 2007 Sep-Oct;20(5):322-9 .

9. J Clin Aesthet Dermatol. 2010 Feb;3(2):22-41 .

10. Photodermatol Photoimmunol Photomed. 2007 Feb;23(1):48-56 .

11. Skin Res Technol. 2009 Aug;15(3):338-45 .