04 February 2009

Just because it's natural doesn't mean it's safe

Green tea is widely reputed to be good for you - many people drink it for its antioxidant properties in an effort to prevent heart disease and cancer. Given the fact that it has been sipped by millions of people in Asia for many generations, green tea certainly seems to be safe. At least by itself.

A study published online today in the journal Blood does nothing to diminish green tea's reputation as an overall tonic, but it does raise an important flag about natural remedies in general. From the press release by the American Society of Hemotology, we find out first why scientists are focusing upon green tea:

Because of its increasing popularity and availability to the public in many formulations, green tea has been increasingly studied to understand its effect on cancer, heart disease, and other conditions. In animal studies, an antioxidant compound in green tea called the EGCG polyphenol (epigallocatechin gallate) has been shown to be a potent anticancer agent, with effects demonstrated against leukemia, as well as lung, prostate, colon, and breast cancer."
So far, so good. But it turns out that some components of green tea may counteract the anticancer effects of one cancer therapy, bortezomib (Velcade®)
"In this study, researchers evaluated whether the combination of green tea and bortezomib would improve outcomes against multiple myeloma, a blood cancer, and glioblastoma, a malignant brain tumor...the team was surprised to find that the EGCG compound seemed to prevent bortezomib from fighting the disease...the two compounds effectively contradicted one another in the cell, leaving nearly 100 percent of the tumor cells intact.
This is not some extreme version of the relevant compound - the authors found that "EGCG blocked bortezomib’s antitumor effects at levels that are commonly achieved with the use of available concentrated green tea supplements (as low as 2.5 μM – which can be attained with two to three 250 mg capsules of green tea extract)."

Of course, this hardly means that everyone should stop drinking green tea. In fact, that would be silly (unless you are taking Velcade, and then you should probably check with your doctor pronto). But it does provide convincing evidence regarding something that has been worrying the mainstream medical community for some years: natural products may be safe, especially in isolation, but they are still chemicals [before reading this post, did you know that green tea contained EGCG polyphenol?] and are likely to interact with other chemicals in unknown ways.

Just because it's natural doesn't mean it's safe.

Cross posted at Open Salon