NEW YORK (Reuters) - Active compounds in green tea may slow down the progression of prostate cancer, researchers reported on Friday.

A woman pours hot water to make green tea at a traditional tea house in Boseong, about 397 km (246 miles) south of Seoul, September 23, 2007. REUTERS/Han Jae-Ho

Capsules made using green tea extracts called polyphenols lowered levels of proteins that tumors use to grow, the researchers found.

Made by Polyphenon Pharma, the capsules called Polyphenon E contain epigallocatechin gallate or EGCG, a green tea extract that has antioxidant properties.

Jim Cardelli of Louisiana State University Health Sciences Center in Shreveport and colleagues tested 26 prostate cancer patients, aged from 41 to 68.

Each took four Polyphenon E capsules a day -- equivalent to drinking 12 cups of green tea -- for about a month before they had their prostates removed.

Blood tests showed levels of three proteins associated with the growth and spread of prostate cancer fell. Hepatocyte growth factor or HGF fell 18.9 percent on average, vascular endothelial growth factor or VEGF fell by 9.9 percent and prostate specific antigen PSA fell by 10.4 percent, they reported in the journal Cancer Prevention Research.

HGF and VEGF are produced when tumors spread and some patients showed “significant” reduction levels of more than 30 percent, Cardelli said.

Few side effects were reported and liver function of the patients remained normal.

“It’s still in an early stage. Green tea can keep cancer from growing very fast, but it may not be able to shrink tumors,” Cardelli said in a telephone interview.

“But it can be a good addition to traditional therapies, like chemo (chemotherapy) or radiation.”

Prostate cancer is the second leading cause of cancer death among American men. The American Cancer Society projects prostate cancer will be diagnosed in 192,280 men and will kill 27,360 in 2009.

The test in 26 prostate cancer patients was a small trial and bigger studies would be needed to confirm the results.