A recent story in a Denver, Colorado, newspaper carried this ominous headline: “Herbal remedy rapped, cancels chemo, researcher says.” According to a pharmacologist at the University of Colorado’s Health Sciences Center, studies in his laboratory showed that hypericin, one of the active ingredients in St. John’s wort (Hypericum perforatum), had been found to interfere with the action of etoposide, a chemotherapy agent used in the treatment of lung, ovarian, and testicular cancer. Ironically, etoposide has its roots in herbal medicine—it’s a synthetic derivative of podophyllin, an extract from mayapple root (Podophyllum peltatum).
Etoposide appears to work by inhibiting an enzyme called topoisomerase II that cancer cells use for repairing their DNA, which in turn allows them to divide rapidly. Inhibiting this enzyme keeps the cancer cells from dividing, thus slowing the growth of the cancer. Through a complex mechanism, hypericin seems to prevent etoposide from achieving this effect. Other than blocking the drug’s action, no negative effects of hypericin were found. There was also no implication that hypericin would cancel out the effect of chemotherapy agents that worked by a different mechanism.
However, based on this finding, the article goes on to state that “the interaction is just one more sign that herbal remedies should be looked upon as medications by the FDA and not as mere supplements.”
While I agree that the laboratory findings may be cause for concern, I do not understand how they lead to the assertion that herbs should be regulated as drugs.
Two questions are left unanswered by the article, questions that should always be asked when a potential herb/drug interaction has been identified.
First of all, is the concentration of the herbal extract similar to what would be achieved in the bloodstream when a person takes the herb in a normal daily dose? Typically, laboratory studies use isolated compounds in high concentrations that may not reflect what occurs in an actual clinical situation. For example, this study looked at pure hypericin, whereas most commercial St. John’s wort products contain only 0.3 percent hypericin, a relatively low concentration.
Second, is the situation in the bloodstream the same as it is in the test tube, or could unexpected variables affect the end result? Human beings are complex systems, and the sum of the parts can very easily be different from the individual ingredients. Consequently, it can be difficult to use a laboratory finding to predict what will happen inside a person.
One pertinent example of this is the use of antioxidant vitamins along with chemotherapy. In the laboratory, many chemotherapy drugs act as cellular poisons. By generating toxins called free radicals, they damage the DNA of cancer cells, causing the cells to die off. Because antioxidants neutralize free radicals, some oncologists have reasoned that antioxidants should be avoided by cancer patients receiving chemotherapy.
This recommendation is problematic. Since it is based on speculation instead of data, there is no way of knowing what an acceptable intake of antioxidants would be. It is conceivable that a patient would be told to avoid eating fruits and vegetables during treatment. They could also be told to avoid green tea (Camellia sinensis), garlic (Allium sativum), and culinary herbs such as rosemary (Rosmarinus officinalis) or turmeric (Curcuma longa), all of which are potent antioxidants. To follow this logic, if the ideal situation for fighting off cancer with chemotherapy is one in which free radical levels are maximized, perhaps patients should be advised to smoke a cigarette or two just before treatment. (Please don’t follow this advice!)
Fortunately, these predictions have not been proven true by clinical studies. In fact, published studies show a bene-ficial interaction between antioxidants and chemotherapy in that patients receiving both have fewer side effects from the chemotherapy and have better response rates. In addition, numerous medicinal herbs such as astragalus (Astragalus membranaceus), Siberian ginseng (Eleuthero-coccus senticosus), milk thistle (Silybum marianum), schisandra (Schisandra chinensis), and echinacea (Echinacea spp.) have all been studied in combination with various chemotherapy agents and shown to either mitigate side effects, enhance effectiveness, or both.
Unfortunately, until further studies can prove or disprove the interaction between etoposide and St. John’s wort, I would have to recommend not combining the two. However, this singular finding cannot be generalized into a warning about the dangers of taking herbs or antioxidant vitamins while receiving anti-cancer drugs. Meanwhile, I patiently wait for the day when this atmo-sphere of antagonism dissolves and oncologists start writing routine prescriptions for broccoli, garlic, and astragalus along with those for chemotherapy.
Labriola, D., et al. “Possible interaction between dietary antioxidants and chemo-therapy.” Oncology 1999, 13:1003–1012.
Lawson, D. W., et al. “Antioxidants in cancer therapy; their actions and interactions with oncologic therapies.” Alternative Medicine Review 1999, 4:304–329.
Prasad, K. N., et al. “High doses of multiple antioxidant vitamins: essential ingredients in improving the efficacy of standard cancer therapy.” Journal of the American College of Nutrition 1999, 18:13–25.
Robert Rountree, M.D., is a physician at the Helios Health Center in Boulder, Colorado, where he practices integrative medicine. He is coauthor of Smart Medicine for a Healthier Child (Avery, 1994), and an Herb Research Foundation advisory board member.
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