The curative powers of green tea have long been touted, but three human clinical trials here seek to scientifically prove - or disprove - that Polyphenon E, a green tea extract, can help prevent cervical cancer, prostate cancer and chronic obstructive pulmonary disease - COPD - a precursor to lung cancer.

"A lot of people say green tea prevents this or prevents that," said Dr. Francisco Garcia, who is heading a cervical cancer study. "We're actually trying to see if that is true."

But Sherry Chow, a co-investigator on the three studies, said, "There is no direct proof yet that green tea can prevent cancer. We're doing the clinical trials necessary to move in that direction."

The green Polyphenon E pills used in the study come from the National Cancer Institute, Chow said. Taking four small pills once a day offers the equivalent of the beneficial properties found in 16 cups of green tea, she said.

Garcia, professor of obstetrics and gynecology at the UA College of Medicine and Arizona Cancer Center member, is working to see if cervical cancer can be prevented, and perhaps even be resolved non-surgically.

In the cervical cancer clinical trial, participants who have persistent human papillomavirus (HPV) infections or other high risks for cervical cancer take the pills for 16 weeks, Garcia said.

Half the participants get Polyphenon E, and half get a placebo, he said.

About 180 women will take part in the study, which is still seeking participants.

Call 318-7178 for more information on getting involved in the study.

"We're looking for people with evidence of persistent HPV infection, abnormal Pap smears, or might have an an abnormal biopsy," Garcia said.

Dr. Frederick Ahmann, a UA professor of medicine and surgery, is leading a study to determine if Polyphenon E could potentially impact prostate cancer.

Study participants are taking Polyphenon E for a few weeks before undergoing surgery to remove their cancerous prostate.

Tissue removed during surgery will be examined to see if the green tea extract reached the prostate and had any effect on tissues there, Ahmann said.

"It's the first step, but an important test, to see if these substances will turn out to be useful," Ahmann said. "There are theoretical benefits right now but we don't know if green tea does anything."

Participants are told the research will not help their situation, but will perhaps help people in the future, he said.

If this test - slated for completion by year's end - is successful, future clinical trials could possibly determine if green tea can prevent or even cure prostate cancer, he said.

The COPD study is assessing whether the green tea pills can reverse some of the damage associated with the disease, said Chow, research associate professor at UA.

COPD, primarily caused by heavy smoking, is a disease that leads to a high risk for developing lung cancer, Chow said.

Dr. Iman Hakim, principal investigator and dean of the UA College of Public Health, is investigating whether green tea intervention can actually reverse some of the airway damage caused by COPD, Chow said.

Green tea components like Polyphenon E - a chemically defined, decaffeinated, catechin-enriched antioxidant green tea extract - are dietary supplements already available to the public, Garcia said.

"The issue is not whether you can get it, but whether it would do anything for you," Garcia said.

"The big thing for me is to not oversell this concept. We are enthusiastic and hopeful, but the whole reason we are doing the trial is to see if these agents, which look so promising in the laboratory, really have a human application."

Ahmann, who is working on a study to see if green tea extract can impact prostate cancer, agrees.

"Dietary supplements can be sold and touted as something you can do to try and help yourself without any true tested evidence that it works,'' Ahmann said.

"We don't believe that is the proper way to decide what people should or shouldn't take. You should test something to see if there is a positive benefit before you suggest someone take something."

And the public should be cautious of the quality of supplements being sold.

"The over-the-counter pills are not controlled by the FDA," Chow said.

"You don't know what is in them. They are so variable."

The National Cancer Institute, part of the National Institutes of Health, has funded the three studies to the tune of $3.2 million, Chow said.

The COPD study has $1.8 million in funding, the cervical cancer study got $1 million and the prostate cancer study received $400,000, she said.

The Arizona Cancer Center led the way in proving that Polyphenon E is safe and could enter the bloodstream, said Chow, who led that investigation.

The Tucson center, which was the first to work with pure Polyphenon E capsules, is also the leader in investigating the preventive properties of the green tea compound, she said.

"We're really excited about each one of our studies," Chow said.