Oral green tea catechin metabolites are incorporated into human skin and protect against UV radiation-induced cutaneous inflammation in association with reduced production of pro-inflammatory eicosanoid 12-hydroxyeicosatetraenoic acid.
Rhodes LE. et al. Br J Nutr. 2013 Sep 14;110(5):891-900. doi: 10.1017/S0007114512006071. Epub 2013 Jan 28.
Green tea catechins (GTC) are antioxidants and they are used as dietary supplements as well as in alternative medicine.
They also reduce UV radiation (UVR)-induced inflammation in experimental models, but the mechanism of protection is unknown.
Human studies are very few and the bioavailability of CTC in the skin is unknown.
METHODS and RESULTS
-16 subjects were enrolled (phototype I/II)
-they received oral GTC (540 mg) with vitamin C (50 mg) daily for 12 weeks.
-Before and after, buttocks were exposed to UV radiation and the erythema was measured.
-Biopsies were taken 24 hours after UV radiation caused erythema. Then three things were done.
-Cutaneous uptake of GTC. Benzoic acid levels were increased in skin fluid post-supplementation (P= 0.03), and several intact catechins were found.
-Protection against erythema (redness) after UV radiation,
-Impact of UV radiation on on inflammation enzymes (cyclo-oxygenase and lipoxygenase-produced), measured by the production of PGE2 and 12-hydroxyeicosatetraenoic acid (12-HETE), respectively. In urine samples:
-Pre-supplementation, PGE2 and 12-HETE were UVR induced
-After GTC, UVR-induced 12-HETE reduced from mean 64 to 41pg/μl (P= 0.01)). There was no effect on PGE2 (Prostaglandin) levels)
Thus, GTC intake results in the incorporation of catechin metabolites into human skin associated with abrogated UVR-induced 12-HETE this may contribute to protection against sunburn inflammation and potentially longer-term UVR-mediated damage.
What is interesting in this study is that it is done in humans and that it measures oral intake of green tea catechins (GTC).
Oral ingestion of green tea up to now DID NOT have enough to show that it is effective for sun protection:
-Nevertheless, this study suggests that some GTC is delivered intact to the skin (bioavailability) after been consumed (ingested) and absorbed by the digestive tract into the blood stream.
-The GTC in the skin would protect against sunburn – we do NOT think that it would replace sunavoidance of application of sunscreens.
-The GTC could potentially protect against long-term UV-induced damage – GTC are antioxidants but they do not replace prevention of sunburn.
Article selection: Prof Dr Jean-Hilaire Saurat – dermatologist. Geneva, Switzerland