A two year trial refutes claims that taking green tea supplements can have a positive effect on photodamaged skin. Green tea extract is well known for its antioxidant qualities and has long been regarded as an ingredient that might help protect the skin against UV damage. But now it seems that it only works as a topical application and oral supplements are a waste of money.
The research was conducted by scientists at Stanford University, California, in collaboration with cosmetics company Nu Skin
which funded the study, and looked at the effects of oral green tea supplements on a number of characteristics associated with UV aging. These included fine and coarse wrinkles, pore size, erythema (skin redness) and collagen levels.
The study included 56 women between the ages of 25 and 75, half of which were randomly assigned the placebo and half the green tea capsules containing 250mg of polyphenols (70 per cent of which were catechins). It seems that some benefits were observed at six months; however, they did not stand the test of time as at 24 months they were no longer present.
On the other hand, research from scientists in Switzerland has looked at the effects of topical application of low concentrations of green tea extracts over a sustained period of time. According to the study, conducted at the University Hospital of Zurich, topical application of green tea extract at 0.4% over a five week period exhibited significant photochemoprotective effects.
The researchers did note however, that the green tea extract did not appear to affect the formation of thymidine dimers – DNA lesions most commonly caused by UV radiation. When lesions such as these go unrepaired they can lead to the formation of skin cancer. If the green tea extract was working as a sunscreen, one would expect the number of UV-induced lesions to decrease. As this is not the case, the researchers concluded that green tea isn't working as a sunscreen at all, but that its protective effects are due to its anti-inflammatory properties and its ability to reduce oxidative damage.