Tue Oct 28, 4:34 PM ET

WASHINGTON (Reuters) - Ginger, green tea and a Chinese herb may all help prevent the development of cancer, researchers told a conference on Tuesday.

The experimental findings -- most coming from experiments on mice -- do not yet merit a change in diet. But they do suggest there are some ways people may be able to further reduce their risk.

Smoking is the No. 1 cause of preventable cancer in many countries, including the United States, and in the developed world experts are starting to agree that poor diet and a lack of exercise run a close second. 

But researchers speaking to a meeting on Phoenix of the American Association for Cancer Research said they were keen to find ways to further lower the risk.

"These studies are extremely important and must be continued to help us understand better ways of preventing cancer which do not require extraordinary measures," Dr. Raymond DuBois of Vanderbilt University in Nashville, who chaired the meeting, said in a statement.

"We're hoping that, armed with this information, individuals will become more proactive about their health on a daily basis, in consultation with their doctors."

Ann Bode and Zigang Dong of the University of Minnesota used a ginger extract on mice infected with human colon cancer cells. The specially bred mice almost always grow tumors.

But when fed extracts of -gingerol -- the substance that makes ginger spicy -- fewer mice grew the tumors.

After 15 days, Bode and Dong counted 13 tumors in mice fed normal diets compared to four tumors in mice fed the ginger extract before and after they were injected with tumor cells.

"As we continue to study the spice in other tumor areas, we hope it will translate into significant anti-cancer properties for humans," Bode said in a statement.

A second group tested the Chinese medicinal herb, Scutellaria barbata or Ban Zhi Lian.

The team at Union College in Nebraska found it slowed the growth of prostate tumors in mice.

A team at the Arizona Cancer Center in Tucson had 118 heavy smokers drink at least four cups a day of both green and black tea and measured a chemical called 8-OHdG, which the body releases in response to DNA damage like the kind that can cause cancer.

Those who drank decaffeinated green tea for four months had a 31 percent reduction in 8-OHdG. Those who drank black tea had no reduction.