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

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

In a demonstration of the plant's anti-cancer properties, investigators smeared broccoli sprout 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 Proceedings of the National Academy of Sciences.

Paul Talalay is a Johns Hopkins University molecular 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 weird 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 whatsoever, because it's a totally different mechanism and one cannot possibly substitute for the other."

Applied as a thick cream, sunscreen protects the skin by deflecting 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 penetrating skin cells and stimulating their natural cancer-fighting mechanism.

Observers call the research promising, but say more studies are needed because the results varied considerably 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 tint.