Herbs and cancer drugs - They may not mix

Many people with cancer turn to dietary supplements such as antioxidant vitamins as well as to plants and plant products. They believe that these may help them fight their disease or counter the side effects of conventional therapies.

This practice concerns cancer experts. Although we tend to think of herbs as “natural” and harmless, in fact they can alter the absorption, distribution, metabolism, and excretion of prescribed drugs. In short, they may interfere with cancer treatment.

Where the problem lies
Many adverse drug interactions revolve around a group of body enzymes, called the P450 system, that play a role in the metabolism of most of the commonly prescribed anti-cancer drugs. If a person taking one of these drugs also uses certain herbal preparations, that might increase the enzymes’ activity, resulting in a decrease in the drug’s concentration and thus a reduction of its effectiveness. On the other hand, the opposite may happen: The potency of an anti-cancer drug may rise to toxic levels, much like an overdose.

Rating the remedies
To see which herbal remedies may pose a problem for anti-cancer drugs, a team of experts at the National Cancer Institute (NCI) looked at the 15 best-selling herbs in the U.S. At right are their evaluations. The bottom line for cancer patients: Check with your doctor before you take any herb or supplement.