A report published online on April 27, 2011 in the Journal of Nutrition describes protective benefits for green tea polyphenols against ultraviolet light-induced skin damage, as well as an ability to improve elasticity, density and other skin properties.
Researchers at the University of Witten-Herdecke and Heinrich Heine University in Germany assigned 60 women with light to normal ultraviolet sensitivity to receive a green tea beverage containing 1,402 milligrams per liter total catechins or a control beverage daily for twelve weeks. Before the treatment period and at six and twelve weeks, participants received a dose of irradiation to the skin from a solar simulator. Reddening, elasticity, roughness, scaling, density and water homeostasis were evaluated at these time points and blood samples were analyzed for flavonoids and other variables.
Ultraviolet-induced reddening of the skin was reduced by 16 percent after six weeks and 25 percent at 12 weeks compared to pretreatment responses among those who received green tea, indicating increased photoprotection. Skin elasticity, density, hydration, blood flow and oxygen saturation increased in those who received green tea, while roughness, volume and scaling declined. A decrease in scaling and volume and an increase in hydration were also observed in the control group; however, the degree of improvement was significantly less than that experienced by women who received green tea.
"Our green tea catechin beverage data are in accordance with the literature reporting protective effects of various polyphenols against UV-induced photo oxidation, induction of inflammation, oxidative stress, and DNA damage from different stress sources in cell cultures and animals," the authors write. "The mechanisms underlying photoprotective effects of flavonoids in humans have not been elucidated; however, they are efficient antioxidants contributing to photoprotection in plants."
"We demonstrated that ingestion of green tea catechins improved skin hydration, transepidermal water loss, density, and elasticity," they observe. "These observed skin changes were probably an outcome associated with long-term consumption of green tea polyphenols and not likely a transitory response."