Introduction
Herbs have been used for medicinal purposes for centuries and anecdotal evidence indicates that they are generally safe for moderate consumption. However, herbs can have potentially dangerous or life-threatening side effects. Unlike prescription drugs, herbal supplements are not subjected to large-scale, rigorous testing. Therefore, it is important to consult a qualified health care provider and to thoroughly investigate the potential hazards before consuming an herbal remedy.
Hypertension
Some popular herbs can negatively affect circulation. These include peppermint, chamomile, aniseed, St. John's wort, licorice root, guarana, parsley, ginger and ginseng. These herbs constrict the blood vessels and may cause changes in blood pressure. These herbs are generally regarded as safe at low doses over a short period of time; however, the Director of the Institute for Traditional Medicine in Oregon states that they can “provoke hypertension”. Consumption of these herbs is contraindicated for individuals with conditions of the circulatory system.
Liver Injury and Veno-Occlusive Disease
The liver processes all substances taken into the body and is highly susceptible to injury. According to the University Hospital of Cincinnati more than 900 drugs, toxins and herbs have been reported to cause liver injury. The risk of liver injury while taking Kava Kava has gained attention in recent years, but long-term use of a variety of herbs can increase the risk of liver damage. For instance, the FDA reports that high intake of herbal teas is a significant risk factor for developing veno-occlusive disease, which is a blockage of the liver veins. Notably, herbal teas containing chaparral, germander, groundsel, skullcap, comfrey, mistletoe and senna are associated with veno-occlusive disease, even in individuals with no prior liver problems.
Drug Interactions
In some instances, herbs can counteract or increase the effects of medications or other herbs and supplements. For example, ginkgo, yucca, garlic and St. John’s wort can interfere with blood-thinning medications, such as warfarin. Other popular herbs, such as valerian, can interact with common antihistamines and anti-inflammatories.The American Association of Nurse Anesthetists indicates that herbs should not be taken at least 2 weeks before surgery. Valerian and St. John’s wort interact with anesthetics and increase sedation, while other common herbs can increase the risk of surgical bleeding or affect the heart and blood pressure. A pharmacist or herbalist should be consulted before using medications and supplements.
Pesticides, Microbes and Heavy Metals
The plant materials used to make herbal remedies can easily become contaminated with pesticides, microbes, molds, E.coli or heavy metals, which can lead to serious illness if consumed. An American supplier must ensure that products conform to The American Herbal Products Association quality standards. Before purchasing an herbal remedy, certificates of lab analysis may be requested in order to guarantee that the supplement is free from microbiological contaminants. To avoid pesticide contamination, only purchase products that have been USDA certified or those that have been grown organically without the use of pesticides. A study in the journal “Trends in Pharmacological Sciences” states that unscreened herbal medicines may contain toxic heavy metals or undeclared prescription drugs. Herbal suppliers should demonstrate evidence that products conform to the safety guidelines established by The American National Standards Institute or other governing body. As with any health decision, the risks and benefits of potential herbal treatments should be considered under the guidance of a qualified health care professional .
References
Centers for Disease Control: Chaparral-Induced Toxic Hepatitis
University Hospital of Cincinnati: Diseases of the Liver
"Handbook of Medicinal Herbs, Second Edition"; James Duke; 2002
Erin Connelly - Since 2003 Erin Connelly has been a writer for university, government and nonprofit publications. She has edited submissions for "Nature," ...
Join the Conversation