Quercetin May Boost Green Tea’s Effect Against Prostate Cancer, Mouse Study Says

December 9, 2013

A new mouse study indicates that quercetin-a flavonoid derived from onions, apples, and red wine-may boost the bioavailability of green tea polyphenols for fighting prostate cancer.

Green tea intake may have chemoprotective properties, but some researchers say green tea’s bioavailability in the body may be limited. However, a new mouse study indicates that quercetin-a flavonoid derived from onions, apples, and red wine-may boost the bioavailability of green tea polyphenols for fighting prostate cancer.

Once in the body, green tea polyphenols such as epigallocatechin (EGC), epigallocatechin-3-gallate (EGCG), epicatechin (EC), and epicatechin-3-gallate (ECG) are readily methylated and excreted via urine. According to the researchers, “methylation significantly decreased the anticarcinogenic activity of EGCG” in prior prostate cell studies. As a result, green tea polyphenols may have lowered bioavailability in the human body; to be effective, they may require higher intake doses than humans may be able to achieve through daily green tea consumption.

The current investigation combining quercetin and green tea included two separate studies. In the first study, mice were inoculated with prostate cancer cells. One week later, they were assigned to one of six treatment groups, 1) control (received a sterilized AIN-93G diet plus water, or “diet”), 2) diet plus “green tea” (equivalent to 5-6 cups of tea daily), 3) diet plus low dose of quercetin (0.2% quercetin), 4) diet plus high dose of quercetin (0.4% quercetin), 5) diet plus green tea and low-dose quercetin, 6) diet plus green tea and high-dose quercetin. The second stud featured the same treatments, only treatment started two weeks prior to inoculating the mice with cancer cells. In both studies, treatments continued for six weeks.

Mice given high-dose quercetin plus green tea experienced a significant inhibition of tumor growth of 38%, the researchers say. They said combining quercetin with green tea “significantly increased the cellular concentrations of non-methylated EGCG in prostate cancer…cells.”

“In previous cell culture experiments, we were able to demonstrate that the combined use of [quercetin] with EGCG dramatically increased the cellular absorption and decreased the methylation of EGCG in prostate cancer LNCaP and PC-3 cells leading to enhanced antiproliferative effect,” they added. “The present study confirmed that the combination of [green tea] and [quercetin] in vivo also increased the anticarcinogenic effect in a dose-dependent manner.” The researchers say human studies are now needed.