Catechins belong to the chemical family of flavonoids, a naturally occurring antioxidant, and a secondary metabolite in certain plants. Green tea catechins are known for their essential anti-inflammatory, photo-protective, antioxidant, and chemo-preventive functions. 

Ultraviolet radiation remains a principal cause and prime concern for damaging the skin. Studies have proved that regular consumption of green tea catechins increases the minimal dose of radiation required to induce erythema. 

There are only a few pieces of research studying the effect of oral supplementation with green tea catechins on ultraviolet radiation-induced skin inflammation in human subjects.

A systematic review and meta-analysis determined the effectiveness of green tea catechins in cutaneous erythema and elucidated whether green tea catechin consumption protects against erythema (sunburn) inflammation. It undertook a comprehensive literature search to identify the relevant studies. It utilized the inputs from two researchers who carried out independent screening, data extraction, and quality assessment according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). 

The pooled data were assessed using approaches fixed-effects or random-effects model to quantify the effectiveness of green tea catechins in the erythema dose-response. 

The Six randomized controlled studies among the enrolled studies that showed regular administration of green tea catechins orally for 6 to 12 weeks in 100 healthy volunteers were included in the analysis. 

The results revealed-

• Green tea catechins show favourable protection against erythema inflammation even at increased minimal erythema dose (MED) of ultraviolet radiation. 
• Meta-analysis results confirmed oral supplementation of green tea catechins to be highly effective at low-intensity ultraviolet radiation-induced erythema response (MED range; 1.25-1.30) compared to placebo, showing a significant pooling difference in erythema index in the random-effects model. 

The study highlighted that the pro-inflammatory signalling pathways through oral supplementation with green tea catechins appear to be an attractive strategy for photo-protection in healthy human subjects and thus could be utilized as a complementary approach to topical sunscreens. The evidence from this study proves that regular green tea catechin supplementation is associated with protection against UV-induced damage due to erythema inflammation.

This meta-analysis also demonstrated that a regular intake of as low as 540 mg of green tea catechins per day could prove beneficial for the protection against ultraviolet radiation-induced erythema, where the green tea catechin metabolites are bioavailable at the dermis and epidermis levels of the skin, increasing the minimal dose of radiation (MED) required to induce erythema. This also suggests that green tea catechins can further strengthen the skin’s tolerance to ultraviolet radiation-induced skin damage from radiation through the prevention of the ultraviolet radiation-induced perturbation of epidermal barrier functions.

Source: Kapoor MP, Sugita M, Fukuzawa Y, Timm D, Ozeki M, Okubo T. Green Tea Catechin Association with Ultraviolet Radiation-Induced Erythema: A Systematic Review and Meta-Analysis. Molecules. 2021 Jun 17;26(12):3702. doi: 10.3390/molecules26123702. PMID: 34204433; PMCID: PMC8233826.