Polyphenols, green tea, and prostate cancer

According to a report on BBC News on Saturday a “chemical found in green tea appears to slow the progression of prostate cancer.”

Over the years, there have been a wide range or articles and some scientific publications suggesting beneficial effects of components in green tea on a whole range of clinical conditions, from Alzheimer’s disease and heart conditions to prostate cancer. The problem has always been a lack of really definitive scientific evidence for such effects.

A paper by McLarty et al., just published in Cancer Prevention Research, does seem to add significantly to our understanding of what is going on here.

The researchers studied the effects of short-term supplementation with the active compounds in green tea on serum biomarkers in 26 patients with prostate cancer. They report that:

  • All the men with had had positive prostate biopsies and were scheduled for radical prostatectomy.
  • The men were given daily doses of a product called Polyphenon E, which contained  a total 1.3 g of tea polyphenols, including 800 mg of (–)-epigallocatechin-3-gallate (EGCG) and lesser amounts of (–)-epicatechin, (–)-epigallocatechin, and (–)-epicatechin-3-gallate until the time of their radical prostatectomies.
  • Serum was collected before initiation of the drug study and on the day of prostatectomy.
  • Serum levels of several biomarkers were analyzed, including PSA, hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), insulin-like growth factor I (IGF-I), and IGF binding protein-3 (IGFBP-3), both at baseline and at the time of surgery.
  • The levels of patients’ liver function enzymes were also monitored, as a method to assess risk of toxicity.

The study results showed that:

  • HGF, VEGF, PSA, IGF-I, and IGFBP-3 levels, and the IGF-I/IGFBP-3 ratio, decreased significantly during the study.
  • All of the liver function tests also decreased, five of them significantly.
  • The decreases in HGF and VEGF levels were confirmed in prostate cancer-associated fibroblasts in vitro.

The authors conclude that their results “show a significant reduction in serum levels of PSA, HGF, and VEGF in men with prostate cancer after brief treatment with EGCG (Polyphenon E), with no elevation of liver enzymes. These findings support a potential role for Polyphenon E in the treatment or prevention of prostate cancer.”

The “New” Prostate Cancer InfoLink is pleased to see that there is now additional evidence in support of polyphenols as agents that can help to affect the progression of prostate cancer in patients with relatively low risk disease. According to a report about this research on MedPage Today, four capsules of Polyphenon E “are equivalent to about 12 cups of green tea.” Apparently the manufacturer of Polyphenon E provided free drug for this study, but the authors report no other conflicts of interest.

Should everyone who thinks that are at risk for or have low-risk prostate cancer rush out this morning an start taking daily doses of Polyphenon E. We think not!

What we have here is evidence of the possibility that certain types of polyphenols may be able to delay the progression of prostate cancer over time. We would need a lot more evidence, specifically including data from randomized, double-blinf, controlled trials, before we would feel comfortable reporting that there was a definitive effect of Polyphenon E on the clinical prevention of prostate cancer.

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