Probing Question: Does lycopene reduce the risk of prostate cancer?

Men who eat plenty of tomato products, especially tomato sauce-laden foods, have a lower risk of prostate cancer. Why? So far, the search for the tomato's "active ingredient" has homed in on lycopene, the molecule that gives tomatoes their red color. "Lycopene accumulates in the prostate. That's its favorite place to hang out," explains Holly Hantz, an undergraduate who is doing research on lycopene's effects. In one of the few cases of processed foods trumping fresh-picked, research suggests that cooking tomatoes, even briefly, releases the lycopene and makes it easier for the body to absorb.

tomatoes
Emily Wiley

Lycopene, the molecule that gives tomatoes their red color, may also be responsible for decreasingthe risk of prostate cancer.

Hantz's adviser, assistant professor of nutrition Keith Martin, points out that "data show that high intakes of tomato-based foods significantly decrease the incidence of prostate cancer. However, whether lycopene alone is beneficial compared to tomatoes or tomato powder is inconclusive." How can we determine whether lycopene is responsible for the anti-cancer properties of tomatoes? "A convincing experiment," says Martin, "is to get some cancer cells, culture them on a dish, deliver some pure lycopene or tomato extract, and see if the cells live or die."

Hantz decided to do just that. She exposed fully developed human prostate cancer cells to lycopene in doses equivalent to the levels present the bloodstream of people who eat two-to- three servings of vegetables daily. The cells showed depressed mitochondrial metabolism within 20 hours, followed by apoptosis, or "orderly cell death." When the lycopene level was raised to the equivalent of five-to-ten servings a day the effect was even more potent. In contrast, cancer cells that received no lycopene maintained the strong metabolism needed for rapid growth and showed no signs of apoptosis. This experiment provided substantial evidence that lycopene itself was a factor in inducing cancer cells to call it quits. Martin concluded, "It appears that lycopene alone can kill cancer cells by inducing programmed death without necessarily affecting cell division."

"In a nutshell, there are numerous benefits to understanding the mechanism of lycopene's protective effect," Martin explains. "Lycopene is a really long molecule that goes into the cell membrane, and that's where many of your receptors are for cell survival and growth. Right now, we are running tests to see which genes are being affected by the lycopene in these cells. If we can find out which signals are affected by lycopene to kill cancer cells, then more effective drugs or nutritional intervention strategies can be designed based on this information.

"The bottom line," says Martin, "is you have to eat your fruits and vegetables, and adding some extra tomatoes is especially good."

Holly Hantz is an undergraduate nutrition major, hlh168@psu.edu. Keith Martin, Ph.D., is assistant professor of nutrition; krm12@psu.edu.

Last Updated April 20, 2005