President Bush might have refused to eat it, but if he wants to ward off skin cancer perhaps he should give Broccoli the benefit of the doubt because new research suggests that it powerfully mitigates against damage done to the skin by UV radiation.
Writing in PNAS, Johns Hopkins researcher Paul Talalay and his colleagues applied a broccoli-extract to small patches of skin on the backs of six volunteers over a three day period. The subjects were all asked to avoid broccoli and other cruciferous vegetables for a week before the study. The treated area, together with a similar-sized untreated area used as a control, was then irradiated with a dose of ultraviolet light and a chromometer, a colour-sensitive device, was used to measure the redness of the skin afterwards.
The team found that the broccoli-treated patches of skin were, on average, 37% less burned (judging by their degree of redness) than the untreated patches of skin. The team have previously found that a component of broccoli, called SF - sulforaphane, can trigger the production of an effect known as a "phase 2 response" in treated cells. This involves switching on genes such as NQO1, GSTA1 and haem oxygenase 1, which are known to protect cells from damage produced by agents like UV.
"This is the first demonstration that a human tissue can be protected directly against a known human carcinogen," Paul Talalay said. "But this is not a sunscreen," he cautions, because it doesn't block UV, just enables cells to better handle its effects. So instead he thinks that the effect might be useful as an add-on in protecting people from UV, especially amongst people at increased risk of skin cancer, such as inidivuals who are immunosuppressed.