"Can we eat our way to cancer prevention? I think so," Frank J. Rauscher III, PhD, tells WebMD. "That's what we're seeing in studies coming out here and in other places."
Rauscher is deputy director of Wistar Institute Cancer Center in Philadelphia. One of the studies that impresses him was a conference report by Can-Lan Sun, MD, a researcher at the University of Southern California.
Sun led a U.S./China research team that studied the effects of drinking green tea. Green tea is rich in chemicals called polyphenols. Animal studies show that polyphenols have potent cancer-fighting effects.
"We don't have any explanation for this," Sun tells WebMD. "At this point I wouldn't recommend taking green tea for people at risk of cancer. We need more study. How much tea is needed for this effect we don't know. We can only say the cancer-free people in this study are quite frequent tea drinkers."
Rauscher says the study takes the anticancer effects of green tea from the laboratory to humans.
"The green tea study is the culmination of an experiment going on for thousands of years," he says. "It shows the cancer-preventive effects of a very complex mixture, green tea. Only in the past 10 years have we identified the active ingredients and confirmed that that these purified polyphenols have an antitumor effect. What we didn't know was whether there is a correlation between drinking the substance, the levels of these compounds, and cancer prevention. Now this has been done."
The green tea study comes on the heels of a report stating that eating a lot of a cooked tomato product -- tomato sauce -- reduces cancer risk. Harvard Medical School researcher Edward Giovannucci, MD, and co-workers showed that men who ate more than two servings of tomato sauce per week had a 23% lower risk of prostate cancer than men who ate less than one serving a week.
So should we start drinking a lot of green tea and eating a lot of tomato sauce? Take it easy, warns Otis Brawley, MD, professor of epidemiology at Emory's Rollins School of Public Health and associate director for cancer control and chief of the solid tumor service at the Winship Cancer Institute.
"I am very cautious about all of this," Brawley tells WebMD. "You can find a correlation, but it doesn't mean that one thing causes the other. The green tea and tomato paste findings are really interesting leads. Ed Giovannucci is my hero because I'm always looking for a reason to eat more pizza. But the only way to really nail down any of these things is to do a clinical trial."
There's a cautionary tale. Some years ago, the dietary supplement beta-carotene was found to have anticancer effects. A clinical trial tested it -- and found that if a person smoked cigarettes, beta-carotene actually increased the risk of lung cancer.
And even green tea has its limits. Another study reported at this week's cancer conference tested green tea as a treatment for advanced prostate cancer. Even though patients drank strong green tea six times a day, it didn't make the cancers any better.
"We were administering green tea to patients in the hope that it would fight cancer," Mayo Clinic researcher Aminah Jatoi, MD, tells WebMD. "We were disappointed to see it didn't have that effect at all."
Foodstuffs aren't the only things that seem to prevent cancer. A conference presentation by Dartmouth Medical School researcher John A. Baron, MD, showed that people who regularly took baby aspirin -- but not regular aspirin -- had a reduced risk of colon cancer.
"The remarkable thing is the dose effect, where less aspirin gets a much stronger preventive effect than more aspirin," Rauscher says. "We are just learning how to use these compounds. The key is to find where you get the most effect at the least dose. The benefit of this aspirin study is to tell us yes, aspirin works to prevent [colon] cancers -- but we have to refine the dosing very carefully."
The new anti-inflammatory drugs Bextra, Celebrex, and Vioxx have a more specific mode of action than aspirin. It's been hoped that they can provide the anticancer effects of aspirin without its side effects. Brawley says the new findings suggest that a low dose of aspirin may not only work better but also avoid side effects at a much lower cost than the new drugs.-->