VOA常速英语2007-Broccoli Extract May Help Prevent Skin Cancer

Researchers say that an extract made from broccoli¹ sprouts³ may prevent skin cancer when applied⁴ directly to the skin.  VOA's Jessica Berman reports scientists say broccoli contains a chemical that stimulates⁵ the body's natural anti-cancer ability.

According to scientists, broccoli contains a chemical called sulphoraphane, which activates⁶ cancer-fighting enzymes⁷ inside cells.  Researchers say the richest source of sulphoraphane is contained in sprouts.

In a demonstration⁸ of the plant's anti-cancer properties, investigators⁹ smeared¹⁰ broccoli sprout² extract on the skin of six volunteers for three days, and then exposed them to high doses of ultraviolet radiation, which is the leading cause of skin cancer. 

They found there was an average 37 percent less redness and sunburn in the patches covered by broccoli extract.  Redness and sunburn are an indication of skin damage that could lead to cancer.

The results of the study are published in the journal Proceedings¹¹ of the National Academy of Sciences.

Paul Talalay is a Johns Hopkins University molecular¹² pharmacologist and the author of the study.  Talalay says sunscreen conferred no protection against the UV rays, but he says that does not mean people should stop using it. 

"We want to avoid under all circumstances people doing weird¹³ things like making broccoli sprout soup and applying to their skin and thinking that they will be protected against the sun," he said.  "They will have not have any protection whatsoever¹⁴, because it's a totally different mechanism¹⁵ and one cannot possibly substitute for the other."

Applied as a thick cream, sunscreen protects the skin by deflecting¹⁶ the sun's harmful rays.  But it must be constantly reapplied to remain effective. 

In contrast, Talalay says, a compound made of broccoli sprouts works by penetrating¹⁷ skin cells and stimulating¹⁸ their natural cancer-fighting mechanism.

Observers call the research promising¹⁹, but say more studies are needed because the results varied²⁰ considerably²¹ among participants, ranging from a low of eight percent to a high of 78 percent protection against sunburn.  Talalay disagrees.

"Everybody knows you go to the beach and you get fried and I go to the beach and nothing happens to me," he added.  "And we are in the same place.  So, the same experiment if done in a large number of individuals would be much more complex.  But I believe that the evidence certainly from animal studies is that we would get absolutely the same result."

Talalay believes if it works in the skin, a sulphoraphane extract from broccoli sprouts is very likely to act as a hedge against cancer in other organs.

Meanwhile, researchers say there are a number of challenges in making a sun cream from broccoli sprouts, not the least of which is figuring out how to get rid of the green tint²².