Green tea may cancel out the benefits of bortezomib

A laboratory study has found that a component of green tea binds to the drug bortezomib and cancels out the ability of the drug to kill myeloma cells. Researchers are advising patients who are taking bortezomib, alone or in combination with other drugs, not to consume any green tea products.

The study looked for evidence that green tea might enhance the effects of bortezomib. The researchers were surprised to find that, at levels easily reached using available green tea products, the ability of bortezomib to kill myeloma cells was completely blocked. The active ingredient of green tea (EGCG) appears to bind to a component of bortezomib (called boronic acid) in such a way that neither green tea nor bortezomib would have any effect.

The effect was seen both in the test tube and in mice. Although this hasn’t been tested on humans, the lead author of the paper said that, “the current evidence is sufficient enough to strongly urge patients undergoing bortezomib therapy to abstain from consuming green tea products, in particular the widely available, highly concentrated green tea and EGCG products that are sold in liquid or capsule form.”

A particular cause for concern is that green tea products will also cancel out side effects of bortezomib, so patients may initially feel better. They will, meanwhile, be unaware that their treatment has been blocked and the myeloma may be progressing. The authors stress that this is specific to bortezomib and there is no evidence of problems with green tea and any other myeloma treatment; and also comment that, “related studies with other types of cancer therapies are promising and green tea extract may actually improve the anticancer effects of other drugs.”

(Source: American Society of Hematology: March 2009)