A team of Johns Hopkins scientists reports in the Oct.
23 issue of the Proceedings of the
National Academy of Sciences that humans can be
protected against the damaging effects of
ultraviolet radiation — the most abundant
cancer-causing agent in our environment — by topical
application of an extract of broccoli sprouts.
The results in human volunteers, backed by parallel
evidence obtained in mice, show that the
degree of erythema, or skin redness, caused by UV rays,
which is an accurate index of the
inflammation and cell damage caused by UV radiation, is
markedly reduced in extract-treated skin.
Importantly, notes investigator Paul Talalay,
professor of
pharmacology, this chemical extract
is not simply a sunscreen. Unlike sunscreens, it does not
absorb UV light and prevent its entry into the
skin. Rather, the extract works inside cells by boosting
the production of a network of protective
enzymes that defend cells against many aspects of UV
damage. Consequently, the effects are long-
lasting; the protection lasts for several days, even after
the extract is no longer present on or in the
skin.
As skin cancer incidence is rising dramatically due to
the escalating exposure of aging
populations to the UV rays of the sun, Talalay said that
"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."
The protective chemical agent in the broccoli sprout
extract is sulforaphane. It was first
identified by Talalay and his colleagues more than 15 years
ago and has been shown to prevent tumor
development in a number of animals treated with
cancer-causing chemicals.
After first testing mouse models of skin cancer to
confirm sulforaphane's protective effects,
Talalay and his team tested six healthy volunteers. Each
was exposed to a pulse of UV radiation on
small patches of skin (less than 1 inch in diameter) that
were either treated or untreated with
different doses of broccoli extract.
At the highest doses, UV-induced redness and
inflammation were reduced by an average of 37
percent. The extracts were protective even when applied
three days prior to UV exposure. The
protection did vary considerably among the subjects,
ranging from 8 percent to 78 percent, which
Talalay notes may be due to genetic differences, local
differences in the skin or other factors such as
dietary habits. He also points out that conventional
sunscreens were essentially ineffective in these
experiments.
This research was funded by the National Institutes of
Health, American Cancer Society,
American Institute for Cancer Research and Lewis B. and
Dorothy Cullman Foundation.
Authors on the paper are Jed Fahey, Zachary Healy,
Scott Wehage, Andrea Benedict, Christine
Min, Albena Dinkova-Kostova and Talalay, all of Johns
Hopkins.
Disclosure: Paul Talalay and Jed Fahey are unpaid
consultants to Brassica Protection Products,
which licenses the technology to produce broccoli sprouts.
Talalay, Fahey and The Johns Hopkins
University are equity owners in BPP, whose chief executive
officer is Antony Talalay, son of Paul.
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