Here’s a bunch of compelling studies about consumption of green tea and photoaging prevention:
A Randomized Controlled Trial of Green Tea Beverages on the In Vivo Radical Scavenging Activity in Human Skin (2017)
Conclusion: To test the effects of green tea on reducing free radical formation in skin, 32 participants were randomized to consume 3 cups daily of either green tea or water for two weeks. Electron paramagnetic resonance spectroscopy was used to measure the free radical scavenging activity in the skin before and after. Those consuming green tea were found to have a 28% higher free radical scavenging capacity in their skin compared to the water group, proving green tea is effective for reducing oxidative stress in human skin which is very important for reducing skin cancer and photodamage.
Note: Technical article explaining the mechanisms through which green tea prevents skin cancer.
Note: Article providing a comprehensive overview of how orally-consumed green tea polyphenols prevent skin cancer by inhibiting UV-induced immunosuppression and the ability of green tea polyphenols to repair UV-induced DNA damage in skin cells.
Note: Technical article explaining how orally consuming green tea prevents skin cancer by speeding up post-UVB exposure DNA repair.
Inhibition of UVB-Induced Skin Tumor Development by Drinking Green Tea Polyphenols is Mediated Through DNA Repair and Subsequent Inhibition of Inflammation (2009)
Note: Technical article explaining how orally consuming green tea prevents skin cancer by speeding up post-UVB exposure DNA repair and inhibiting post-UVB exposure inflammation.
Note: Comprehensive article covering the research confirming green tea’s photoprotective effects on skin.
Tea Consumption and Basal Cell and Squamous Cell Skin Cancer: Results of a Case Control Study (2007)
Conclusion: Tea consumption rates were evaluated and compared for 770 people with basal cell carcinoma (BCC) skin cancer, 696 people with squamous cell carcinoma (SCC) skin cancer, and 715 controls with no skin cancer. After adjusting for age, sex, and sunburn history, researchers found that regular tea drinkers had a significantly lower incidence of SCC skin cancer, and there was an even lower risk among life-long tea drinkers and heavier tea drinkers. A less significant relationship was found between tea consumption and BCC skin cancer.
Orally Administered Green Tea Polyphenols Prevent Ultraviolet Radiation-Induced Skin Cancer in Mice Through Activation of Cytotoxic T Cells and Inhibition of Angiogenesis in Tumors (2005)
Conclusion: Two groups of hairless mice were UVB-irradiated daily for 10 days and then 3x per week for six months to intentionally initiate and promote skin cancer. One group was given plain water to drink during this time, the other group was given water infused with green tea polyphenols. The green tea group suffered 35% fewer tumors, 63% less tumor multiplicity, and 55% less tumor growth compared to the plain water group. They also experienced reduced expression of matrix metalloproteinases (MMPs), the enzymes that break down skin collagen. “Green tea polyphenols have potential for development as a complementary and alternative medicine to prevent UV-induced nonmelanoma and melanoma skin cancers.”
The Green Tea Polyphenol (-)-Epigallocatechin Gallate and Green Tea Can Protect Human Cellular DNA from Ultraviolet and Visible Radiation-Induced Damage (2005)
Conclusion: This study found that human peripheral blood cells demonstrate decreased DNA damage post-UVR exposure after ingesting green tea. “The studies showed that green tea and/or some constituents can offer some protection against UV‐induced DNA damage in human cell cultures and also in human peripheral blood samples taken post‐tea ingestion.”
Anti-Proliferative and Proapoptotic Effects of (-)-Epigallocatechin-3-Gallate on Human Melanoma: Possible Implications for the Chemoprevention of Melanoma (2004)
Conclusion: This study found that epigallocatechin‐3‐gallate, the major antioxidant in green tea, kills melanoma cancer cells in vitro by inhibiting proliferation and inducing apoptosis. Researchers state that drinking 4-6 cups of green tea daily is necessary to receive these benefits.
Green Tea Polyphenols Prevent Ultraviolet Light-Induced Oxidative Damage and Matrix Metalloproteinases Expression in Mouse Skin (2004)
Conclusion: This experiment testing the capability of orally-consumed green tea polyphenols to prevent UV-induced photodamage in mice found that green tea provides a photoprotective effect by inhibiting oxidative damage to skin from sun exposure and also reducing the expression of UV-induced matrix metalloproteinases (MMPs), which cause the breakdown of skin collagen.
Conclusion: 10 separate experiments were carried out in this study testing the effects of various oral and IP injection green tea preparations on UV-induced and chemically-induced skin cancer in hairless mice. In half of the studies, giving the mice green tea resulted in either complete regression of skin cancer tumor or 90+% inhibition of tumor growth compared to control mice. The other half of studies found green tea effective for inhibiting tumor growth by 46-89% compared to the control mice.
Inhibitory Effect of Green Tea in the Drinking Water on Tumorigenesis by Ultraviolet Light and 12-O-Tetradecanoylphorbol-13-acetate in the Skin of SKH-1 Mice (1992)
Conclusion: Hairless mice were irradiated with UVB to intentionally induce severe photodamage and photocarcinogenesis and given green tea in their drinking water during this time to test the effectiveness of green tea at different brew strengths for preventing and healing photodamage and skin cancer. Researchers found as the green tea brew strength increased, so did it’s protective effect against sunburn. The UVB-induced red skin lesions in the mice given green tea were smaller and lighter in color compared to the plain water control group and the mice given stronger green tea enjoyed much better photoprotective effects compared to mice given a weaker green tea. More amazingly, the mice exclusively given green tea as drinking water developed skin tumors 55-93% smaller than the control group (depending on the tea concentration) and suffered 55% fewer number of tumors. Both weak green tea and strong green tea were also found to be completely effective for totally preventing the formation of basal cell carcinoma (BCC) skin cancer in all mice groups.