Antioxidants and Skin
6.3 Polyphenols: Cocoa and Green Tea
Several antioxidants given systemically or topically as enriched food and supplements have been demonstrated to provide photoprotection. They include flavanols, carote- noids, tocopherols, and vitamin C (Dinkova-Kostova 2008; Sies and Stahl 2004;
Nichols and Katiyar SK: Skin photoprotection by natural polyphenols: anti-inflammatory, antioxidant, DNA repair mechanisms. Arch Dermatol Res. 07 November 2009).
Flavonoids comprise a group of secondary plant constituents widespread in nature and available from dietary sources such as cocoa, green tea, soy, berries, or other fruit (Manach et al. 2004). Flavonoid-containing phytomedicines are used as antiinflam- matory and antiallergic remedies, and a flavonoid-rich diet is suggested to play a role in the prevention of several kinds of cancer and cardiovascular disorders. Many of the alleged effects have been linked to the antioxidant properties of flavonoids, but they also exhibit other biological activities (Stevenson and Hurst 2007).
A study with high- and low-flavanol cocoa products demonstrated that ingestion of dietary flavanols from cocoa contributes to endogenous photoprotection and
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improves dermal blood circulation (Heinrich et al. 2006a; Neukam et al. 2007).
Also, cocoa flavanols affect the cosmetically relevant parameters of skin surface and hydration. Flavonoids are used in common cosmetics primarily for their antioxidant and soothing actions.
In vitro and animal studies have provided evidence that tea flavanols, when applied orally or topically, ameliorate adverse skin reactions following UV exposure, including skin damage, erythema, and lipid peroxidation (Katiyar et al.
2000). Topical application of green tea polyphenols to human skin have inhibited the UVB-induced erythema response and decreased formation of cyclobutane pyrimidine dimers in skin, found in both epidermis and dermis (Hsu 2005).
Pretreatment of skin with green tea extracts led to a lower number of sunburned cells after exposure to solar-simulated radiation with a minimum erythema dose (MED) of 2 and protected epidermal Langerhans cells from UV damage. Green tea polyphenols applied topically have been shown to protect DNA and prevent other damaging effects of UV light such as sunburn response, immunosuppression, and photoaging of the skin (Yusuf et al. 2007). Given the results of previous studies, there is strong evidence to support the concept that the consumption of dietary flavonoids from tea may confer photoprotection and improve skin quality.
In a previous study (Heinrich et al. 2006a) two groups of volunteers consumed either high-polyphenol (326 mg/day) or low-polyphenol (27 mg/day) cacao powder over a period of 12 weeks. Photoprotective effects and parameters of skin condition were measured. UV-induced erythema following exposure of selected skin areas to 1.25 MED was significantly decreased in the high-polyphenol group after 6 and 12 weeks of treatment; no change was found in the low-polyphenol group. Ingestion of high-polyphenol cacao powder led to an increase in the blood flow of cutaneous and subcutaneous tissues, whereas no change in blood flow was found in the low- polyphenol group. Supplementation with high-polyphenol cacao powder results in a significant increase in skin density and thickness. Neither parameter was affected in the low-polyphenol group. Evaluation of the skin surface showed a significant decrease of skin roughness in the high-polyphenol group, whereas no change was found in the low-polyphenol group comparing the starting values with weeks 6 and 12.
No difference was found in the low-polyphenol group. The presented data show that ingestion of dietary polyphenols from cacao contributes to endogenous photo- protection and improves blood circulation in skin. Cacao polyphenols further affect cosmetically relevant parameters of skin surface and hydration.
In a second study (Neukam et al. 2007), the acute effects of a single dose of cocoa rich in flavanols on dermal microcirculation were investigated. In a crossover design study, 10 healthy women ingested a cocoa drink with a high (329 mg) or low (27 mg) content of flavanols. The major flavanol monomer in both drinks was (−)-epicatechin: 61 mg/dl in the high-flavanol product and 6.6 mg/dl in the low flavanol product. Dermal blood flow and oxygen saturation were examined by laser Doppler flowmetry and spectroscopically at 1 mm skin depth at 0, 1, 2, 4, and 6 h.
At the same time points, the plasma levels of total epicatechin (free compound plus conjugates) were measured by means of HPLC. Subsequent to the intake of high-flavanol cocoa, dermal blood flow was significantly increased (by 1.7-fold) at 2 h and oxygen saturation was elevated 1.8-fold. No statistically significant changes
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were found with intake of low-flavanol cocoa. Maximum plasma levels of total epicatechin were observed 1 h after ingestion of the high-flavanol cocoa drink, 11.6 ± 7.4 nmol/l at baseline and 62.9 ± 35.8 nmol/l at 1 h. No change of total epicat- echin was found in the low-flavanol group (Fig. 6.1a, b). The results led to the conclusion that flavanol-rich cocoa acutely improves dermal blood flow and oxygen saturation. Dietary flavanols may contribute to the maintenance of skin health and may influence skin appearance.
Time (h)
0 1 2 3 4 5 6
Relative Blood Flow (AU)
10 20 30 40 50
a 60
b
*
Time (h)
0 1 2 3 4 5 6
Epicatechin - Plasma (nmol/L) 20 40 60 80
100
*
*
*
Fig. 6.1 Effect of high an low flavanol cocoa on cutaneous blood flow and plasma levels of total epicatechin. (a) Peripheral blood flow in skin (1 mm depth) after ingestion of a single dose of high-flavanol (filled circles) or low-flavanol (open circles) cocoa drink (n = 10). (b) Plasma levels of total epicatechin (free epicatechin plus glucuronate and sulfate conjugates) after ingestion of a single dose of high-flavanol (filled circles) or low-flavanol (open circles) cocoa drink (n = 10).
*Significantly different from the low-flavanol group
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In a recent study, 60 volunteers were randomized into an intervention or control group. Over a period of 12 weeks, subjects consumed a drink with green tea poly- phenols. Photoprotection parameters, skin structure, and function were measured at baseline (weeks 0, 6, and 12. Following exposure of the skin areas to 1.25 MED of radiation from a solar simulator, UV-induced erythema was significantly decreased in the intervention group. Skin structural parameters that were positively influenced included elasticity, density, roughness and scaling, and water homeostasis. Long- term intake of the green tea polyphenol beverage increased blood flow in the skin (article in preparation).