Brocolli Sprout Extract Protects Skin Against Damage From Ultraviolet Radiation
The study is published in the 23rd October issue of the Proceedings of the National Academy of Sciences and is the work of Dr Paul Talalay, professor of pharmacology at Johns Hopkins University, Baltimore, Maryland, and colleagues.
UV radiation (UVR) has the ability to cause cancer in several different ways. It damages DNA, causes increase in oxidants that damage lipids and other vital cell components, it causes inflammation and it suppresses the immune system.
Scientists maintain that the dramatic increase in recent years of non-melanoma skin cancers is due in the most part to people living longer and accumulating more total exposure time to the sun's damaging UVR rays over their lifetime. Thus studies such as this are vital to find ways to protect the skin, at the cellular level, against the damaging effects of UVR, wrote the researchers.
Using laboratory mice and human volunteers, the researchers showed that the degree of UVR induced skin redness (erythema), a convenient, accurate and noninvasive way to assess UVR damage, is significantly reduced when the skin has been treated with the broccoli sprout extract, sulforaphane.
Talalay explained that the broccoli extract is not a sunscreen. Sunscreens absorb UVR and stop it entering the skin. The broccoli extract works inside the skin cells, boosting the production of enzymes that protect against UVR. The effect lasts much longer than a sunscreen, for several days at a time, and just as importantly even after the extract has vanished from the surface of the skin.
Referring to the worrying rise in skin cancer incidence, Talalay said:
"Treatment with this broccoli sprout extract might be another protective measure that alleviates the skin damage caused by UV radiation and thereby decreases our long-term risk of developing cancer."
Talalay first discovered sulforaphane over 15 years ago, since when it has been shown to stop tumours growing in animals treated with carcinogenic chemicals.
The researchers first tested the effect of the broccoli extract on mice, where it was found to "up-regulate phase 2 enzymes" and protect against inflammation and edema.
They then recruited 6 human volunteers (three men and three women, aged between 28 and 53 years) and exposed each to a pulse of "narrow-band 311-nm" UVR on small areas of exposed skin, some of which had been treated with different doses of the broccoli extract and some of which had not.
At the highest doses of sulforaphane, the erythema and inflammation caused by the UVR were reduced by 37 per cent on average. There was a wide range in levels of protection, from 8 to 78 per cent, which the researchers suggest could be due to genetic differences in the subjects, differences in the areas of skin, or other factors such as diet.
The protection was still effective when the UVR exposure occurred three days after the sulforaphane was applied to the skin patches. The researchers said that conventional sunscreens showed no protective effects in these experiments.
"Sulforaphane mobilizes cellular defenses that protect skin against damage by UV radiation."
Paul Talalay, Jed W. Fahey, Zachary R. Healy, Scott L. Wehage, Andrea L. Benedict, Christine Min, and Albena T. Dinkova-Kostova.
PNAS published October 23, 2007
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