Quercetin boosts inhibitory effect of green tea for prostate cancer

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27.01.2014

Men in the early stages of prostate cancer may be able to slow down the course of their disease by drinking five cups of green tea and taking one gram quercetin daily. Experiments on mice brought nutritionists at the University of California in Los Angeles to this conclusion. Their research will be published in 2014 in the Journal of Nutritional Biochemistry.
In 2006 Italian researchers at the University of Parma published the results of an experiment in which they had given 60 men in the early stages of prostate cancer a placebo or a daily dose of 600 mg green tea extract for a year. [Cancer Res. 2006 Jan 15;66(2):1234-40.] At the end of the year that the trial lasted the researchers found tumours in 9 of the 30 men in the placebo group, but only 1 tumour among the 30 men who had taken the green tea extract.

Green tea protects against prostate cancer the Italian trial would seem to suggest. But if you look at the epidemiological studies on the subject you'll notice that green tea has no protective effect just as often as it does protect against prostate cancer. [Mol Nutr Food Res. 2011 Jun;55(6):905-20.]

This may be because some men's bodies rapidly convert the bioactive substances in tea – see a few of them below – into less active components. This is partly due to the enzyme catechol-O-methyltransferase [COMT for short], which attaches methyl groups to the compounds in tea thus reducing their cancer-inhibitory effect.

Men in the early stages of prostate cancer may be able to slow down the course of their disease by drinking five cups of green tea and taking one gram quercetin daily. Experiments on mice brought nutritionists at the University of California in Los Angeles to this conclusion. Their research will be published in 2014 in the Journal of Nutritional Biochemistry.
Researchers at the University of California wondered whether they could enhance the protective effect of green tea by adding the flavonoid quercetin [structural formula shown here]. Quercetin reduces the effect of COMT.

The Americans tested their theory on mice that they had injected with prostate cancer cells. The animals in the experimental group were given an extract of green tea [GT] in their drinking water. The human equivalent of the dose that the mice were given was 5-6 cups of green tea a day.

Some of the mice were given food that contained 0.2 or 0.4 percent quercetin. The human equivalent of the doses that the mice were given was 1 or 2 g quercetin per day.

The figure below shows that the green tea extract slowed down the growth of the tumour, and that the inhibitory effect of the extract increased the more quercetin the mice had in their food.

Men in the early stages of prostate cancer may be able to slow down the course of their disease by drinking five cups of green tea and taking one gram quercetin daily. Experiments on mice brought nutritionists at the University of California in Los Angeles to this conclusion. Their research will be published in 2014 in the Journal of Nutritional Biochemistry.

Men in the early stages of prostate cancer may be able to slow down the course of their disease by drinking five cups of green tea and taking one gram quercetin daily. Experiments on mice brought nutritionists at the University of California in Los Angeles to this conclusion. Their research will be published in 2014 in the Journal of Nutritional Biochemistry.

The figure above shows that the more quercetin the mice had been given, the more bioactive ingredients from the green tea the researchers found in the tumours.

The researchers were also able to ascertain that administration of both quercetin and green tea extract inhibited the body’s synthesis of COMT, and boosted the activity of suicide genes in the tumour cells.

"These results warrant future human intervention studies to confirm the combined effect of green tea and quercetin in prostate cancer prevention and treatment", the researchers write.

Source:
J Nutr Biochem. 2014 Jan;25(1):73-80.

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