Several components of the tomato work together to help fight prostate cancer, according to new research.

Previously it had been thought that the chemical lycopene was solely responsible for tomatoes' potential anti-cancer effects.

However, researchers at the Universities of Illinois and Ohio State have discovered that lycopene's effect is enhanced by other components of the fruit, reported BBC News Online.

"It has been unclear whether lycopene itself is protective," lead researcher Professor John Erdman was quoted by the BBC as saying.

"This study suggests that lycopene is one factor involved in reducing the risk of prostate cancer. But it also suggests that taking lycopene as a dietary supplement is not as effective as eating whole tomatoes.

"We believe people should consume whole tomato products - in pastas, in salads, in tomato juice and even on pizza," Erdman said.

The research, reported on in the Journal of the National Cancer Institute, involved exposing laboratory rats to a chemical that causes prostate cancer, and then feeding them on diets containing whole tomato powder, pure lycopene, or no lycopene at all.

At the end of the study, prostate cancer had killed 80% of the control group, 72% of the lycopene-fed rats and 62% of the tomato powder-fed rats, the BBC said.