LAS VEGAS Beware the cosmeceutical claims about green tea and its antiaging properties.
Although there is strong evidence that green tea contains substances that may ward off UVA-related skin damage, it is all from in vitro experiments, Dr. Cherie Ditre said at the annual meeting of the American Society of Cosmetic Dermatology and Aesthetic Surgery.
None of it comes from actual patient trials.
"This is all done with artificial skin and artificial-skin substrates. More work needs to be done," said Dr. Ditre, director of the University of Pennsylvania Health System's Cosmetic Dermatology and Skin Enhancement Center in Radnor.
With that caveat, Dr. Ditre said that green tea has been shown to have strong antioncogenic properties and may work in a complementary fashion to retinoids.
The most important, active component of green tea is considered to be epigallocatechin-3-gallate, or ECGC, which is a polyphenolic compound. It appears to inhibit the generation of intracellular hydrogen peroxide, one of the most active DNA-damaging oxygen species, and the formation of cyclobutane pyrimidine dimer, another source of DNA damage.
In experiments with hairless mice prone to squamous cell carcinoma, application of green tea reduced the development of tumors by 60%, relative to controls (Neoplasia 2003;5:555-65), she said.
In the skin culture systems, topical application of green tea extract of ECGC, at practical doses, has been shown to increase the expression of tissue inhibitors of matrix metalloproteinases (TIMPs). Matrix metalloproteinases contribute to the degradation of collagen, and their levels increase after UV exposure, so they may be an important pathway for sun-induced aging, Dr. Ditre said.
In particular, ECGC was shown to increase production of TIMPs in dermal fibroblasts in response to UVA exposure (J. Dermatol. Sci. 2005;40:195-204).
This is different from how retinoids work, she added. Retinoids upregulate collagen synthesis and downregulate matrix metalloproteinase expression. Matrix metalloproteinase expression is mostly increased as a result of UVB exposure.
These differences suggest that using green tea and a retinoid together could be advantageous.
"There is some harmony between these agents," Dr. Ditre said. "Perhaps the combination of retinoids with green tea could give us the maximum benefit for collagen preservation and perhaps collagen upregulation."
Dr. Ditre disclosed that she serves on the speakers' bureau and is an adviser for Topix Pharmaceuticals Inc., maker of Replenix, a skin-care line containing green tea.