From San Francisco, at a meeting of the American Association for Cancer Research
St. John's wort, the popular herbal remedy for mild depression, lowers the effectiveness of a cancer-fighting drug, according to a study in the Netherlands.
This previously unrecognized downside results from the herb's stimulation of an enzyme in the body called cytochrome P450. That enzyme breaks down certain drugs, including irinotecan, a chemotherapy drug used against various cancers, says Ron A.H.J. Mathijssen, a physician at the Rotterdam Cancer Institute.