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October 2021

Natural Medicines to Avoid During Cancer Treatment

The notion that “natural” products are generally safe remains a popular misconception. It’s a particularly risky one for patients undergoing cancer treatment. Talk to patients about the natural medicines they want to try to ensure they don’t cause more harm than good. In light of Breast Cancer Awareness Month, here are a few to keep an eye on.

CYP3A4 is the most common enzyme involved in drug metabolism, including the metabolism of many cancer therapies. But many natural medicines can also affect this enzyme. St. John’s wort is one of them. It’s commonly used for depression, so patients undergoing treatment for cancer might be tempted to try it. Make sure patients understand that it can increase how quickly the body breaks down many drugs, including cancer drugs such as docetaxel and irinotecan. This can make these drugs less effective and increase the risk of treatment failure. Grapefruit and grapefruit juice can also affect how the body processes certain cancer drugs, potentially altering their safety and effectiveness. Stay on the safe side and tell patients to steer clear of St. John’s wort and grapefruit.

Also keep an eye on antioxidants such as vitamin C and coenzyme Q10. Whether antioxidants help or hurt cancer treatment remains somewhat controversial. Proponents of antioxidants claim that they can protect healthy cells from the negative effects of cancer drugs. But there’s concern that antioxidants might also interfere with the effectiveness of these drugs. For example, some cancer drugs work by generating oxygen radicals that damage tumors. Coenzyme Q10 might protect tumor cells from the effects of these drugs, making them less effective. Most of these concerns remain theoretical at this point, but until more is known, tell patients that the interaction risk seems to outweigh any potential benefits.

Lastly, watch out for probiotics. Many cancer therapies suppress the immune system. This makes patients more prone to infections than healthy individuals. Probiotics are often overlooked as a potential concern because they’re generally considered safe to try. But probiotics are actually live bacteria and using them while immunosuppressed can increase the risk for infection. Many of these patients also have lines and ports, which can become contaminated when probiotic powders are prepared nearby. For these patients, just being exposed to a powdered probiotic can be a concern. Tell patients to avoid exposure to probiotics while undergoing cancer treatment.

It’s important to keep the lines of communication open. Healthcare providers should encourage patients to discuss the natural medicines they’re interested in while undergoing cancer treatment. Some should be avoided, but there’s evidence that others can help. Check out our CE/CME on Advising Patients on the Use of Natural Medicines and Alternative Therapies for Cancer to learn more.

The information in this brief report is intended for informational purposes only, and is meant to help users better understand health concerns. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions. Copyright © 2021 Natural Medicines Inc. Commercial distribution or reproduction prohibited. Natural Medicines is the leading provider of high-quality, evidence-based, clinically-relevant information on natural medicine, dietary supplements, herbs, vitamins, minerals, functional foods, diets, complementary practices, CAM modalities, exercises and medical conditions. Monograph sections include interactions with herbs, drugs, foods and labs, contraindications, depletions, dosing, toxicology, adverse effects, pregnancy and lactation data, synonyms, safety and effectiveness.