First green tea may have anti-cancer properties. Now it turns out, according to a pre-pub in the ASH journal Blood, that polyphenols in green tea can interfere with cancer treatments.

Researchers in California wanted to determine whether multiple myeloma patients taking Velcade (bortezomib, a proteasome inhibitor) and self-medicating with green tea to add to the anti-cancer fight would yield increased antitumor efficacy in MM and glioblastoma (of Ted Kennedy fame), or if it was just placebo.

To their surprised, they discovered that various green tea constiuents - particularly EGCG and related polyphenols - prevented Velcade-induced tumor cell death. "EGCG directly reacted with bortezomib and blocked its proteasome inhibitory function; as a consequence, bortezomib could not trigger endoplasmic reticulum stress or caspase-7 activation, and did not induce tumor cell death," the authors wrote. (This only affected boronic acid proteasome inhibitors, not non-BAP inhibitors.)

The authors conclude, "Taken together, our results indicate that green tea polyphenols may have the potential to negate the therapeutic efficacy of bortezomib and suggest that consumption of green tea products may be contraindicated during cancer therapy with bortezomib."

Green tea has been held up as the solution to many health problems - its antioxidant properties have been touted as beneficial in everything from dandruff and psoriasis to diabetes and heart disease.

See the News Staff post for even more information.