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Are plants safe?

No blanket statement can be made to settle this question.  Well intentioned, yet equally misinformed parties have argued either that herbs are safe because they are “natural” and “more gentle” medicinal tools, or that they are dangerous because their effects are largely “unknown” or “unsubstantiated.”  Neither statement aids in the discussion of herbal safety.

To use plants therapeutically implies an expectation that they will have a physiological effect.  Potential safety problems may arise from inherent toxicity of the plant. Most of those used in popular health care are chosen because they are known to be safe (they have low 'acute toxicity'). However it is not easy to rule out long term or chronic toxic effects as these are difficult to identify in everyday use. Only modern large-scale computer-based monitoring schemes can begin to pick up potentially hidden risks. Even here well-known problems of under-reporting and other biases mean that such risks may still be difficult to identify.

The question remains then, will the effects of plant medicines be beneficial or harmful? There is no single answer that is true for every person: this is the case for the effects of herbs, pharmaceuticals, or common groceries.  Unique individuals with unique bodies will have unique responses.  So how can you begin to assess your own personal risk when using herbs? 

Here are some general guidelines to consider. These are followed by day-to-day tips for prudent use.

Use this database – An educated consumer is a wise consumer.  By consulting EXTRACT, you are already taking the most important step in understanding how to use herbs safely.  Each herb monograph includes a summary on the safety considerations of that particular plant.  Special attention is given to using the herb while pregnant or breastfeeding, possible overdosing, and common side effects.  Safety information in EXTRACT is constantly updated and is derived from the world’s most authoritative reviews of herbal safety, including the World Health Organization and the Medicines and Healthcare Products Regulatory Agency in the UK.  Consumers and health care practitioners who are interested in reviewing the studies and data on which EXTRACT’s monographs are based are encouraged to consider a subscription membership to the database.

Consult a professional – Inform your physician about your interest.  Print off the appropriate pages from this website and hand it in - they will be useful for any health care professional. Click here for tips on how to initiate and conduct a constructive conversation with your doctor about medicinal plant use.

The best possible resource to advise on the safe and effective use of therapeutic plants is a well-qualified professional specialist practitioner.  He or she be able to identify and prevent potential problems and interactions, and also help to choose appropriate herbs for you as an individual and aid in the monitoring of progress.  To learn more about finding and seeing a professional herbalist, click here.

Critique your herbal product – Some of the most serious safety concerns about using herbs involves the proper identification, processing and labeling of plant material.  Therapeutic herbal products are a largely unregulated industry, raising serious questions about the quality of the plant material and the validity of production methods. Avoid obtaining your remedies from someone who promises too much. Plant remedies have gentle supportive effects – they are not miracle workers. Those who claim miracles are thinking more of themselves than of you! Probably the most commonly documented reason for toxic or adverse reactions to herbal products is the presence of adulterants defined as the intentional or unintentional presence of undeclared ingredients which impact adversely on the safety of the product. This adulteration may be due to:

  • Unintentional or intentional substitution of one or more herbal ingredients with toxic species.

  • Intentional addition of a conventional chemical drug, either of natural or synthetic origin.

  • Environmental contamination of the herb with a chemical or pathogen.

  • Intentional addition of a “natural” active component which is responsible for the adverse reaction, such as a microorganism, mineral or nutrient.

For this reason the single most useful measure to reduce the risks of consuming plant-based remedies is to ensure verified standards of production (see quality issues). The EXTRACT team is will produce a list of reputable, independently certified herbal products to help consumers to find appropriate quality products.  Watch this space for updates on this endeavor.  In the meantime, consumers are encouraged to learn as much as possible about the plant they want to use and the company they choose to support.  For information on how to identify a particular plant, see the “What is it” section of our individual plant monographs.

Not all herbal medicines are “time tested” or “ancient” remedies – A long record of historical medicinal use provides invaluable clues as to how a plant can be used safely.  It is not illogical to assume that if a plant has be used by humans for thousands of years, that the most immediate threats of toxicity were extensively examined.  If administered in an approximate equal dose with similar preparation methods to its historical roots, then one can consume the herb with reasonable reassurance of its safety.  However, many herbs on the market have not been used historically or are being manufactured with new methods that alter the dose, constituent make-up and potentially the activity of the plant in the body.  When assessing potential risks of a herbal remedy, consumers are wise to consider not only the available scientific data, but also traditional use data.  EXTRACT is a unique resource that offers evaluation from both positions.  The summary of traditional and historical use under “What does this plant do” section of each plant monograph can help consumers determine how their intended use of the herb compares with how it has been used over time and across the globe.

Consider your specific situation – Don’t forget to assess your overall health.  Are you currently taking medication whose dosage is critical for your health (with a small ‘therapeutic window’) that could be interrupted by adding another medicinal agent?  Are you pregnant or breastfeeding?  Are you attempting to treat a potentially life threatening or acute condition?  If so, you are greatly increasing your risk of complications and safety concerns.  Seek appropriate medical counsel and be aware of the limitations and risks of self care.

Maintain PerspectiveIn 2006 the World Health Organisation’s Collaborating Centre for International Drug Monitoring in Uppsala has received 3.6 million ADR reports from around the world. Of these over 41,000 (1.1%) have listed a herbal drug and just over 17,000 (0.5%) where a herbal drug is listed as suspected or interacting. Their Director has reported that the adverse drug reactions (ADRs) most often associated with herbs were generally minor: pruritus, urticaria and rash, nausea, vomiting, abdominal pain and diarrhoea and dyspnoea. “Very rare” serious symptoms included facial oedema, angioedema and anaphylactic shock, hepatitis, purpura, thrombocytopenia, Stevens Johnson syndrome, convulsions, erythema multiforme and circulatory failure. Most herbal ADRs per head of population arise from France and Germany where herbal medicine is part of the healthcare system and where the true level of herbal ADRs relative to those of synthetic drugs might be clearer; yet even here the levels of reports are very low.


Prudent use

In addition to the preliminary advice above expert experience of plant medicines leads to the following recommendations to reduce risks in day-to-day use.

  • Take your prescribed medicine at different times from your plant remedies (ideally separating them by an hour or more).

  • Do not take your plant remedies for more than three months without getting expert opinion or at least without a break of one month.

  • If you notice anything uncomfortable or have minor adverse effects after taking your plant remedy stop treatment and get expert advice if possible. At the very least take a break before restarting and stop immediately if the discomfort resumes.

  • In the unlikely event that you get a more serious adverse event that you associate with taking your plant remedy you should tell your healthcare professional. This information is useful and there may also need to be follow up in your case.

  • Be wary of taking plant remedies if you have had liver or kidney disease or suffer alcohol or recreational drug damage.

  • Do not take any plant remedies without close expert monitoring if you are being prescribed blood-thinning medicines, digoxin, insulin, anti-epileptic drugs, anti-HIV drugs, anti-rejection drugs, chemotherapy, or within 2 days of a general anaesthetic.

  • Do not take plant remedies in the first 3 months of pregnancy without good expert advice and monitoring and try to avoid such remedies at any time during pregnancy or lactation.

Further resources

The government’s medicines regulator in the United Kingdom, The Medicines and Healthcare products Regulatory Agency (MHRA) has become particularly involved in the herbal sector. It has produced general safety advice to consumers as well as a more substantial report on the Safety of herbal medicinal products. The report opens with the paragraph:In general, most herbal medicinal products are unlikely to pose a significant threat to human health…

The supervising editors of the PlantοMedicine site have produced a comprehensive review of the subject: The Essential Guide to Herbal Safety, published by Elsevier/Churchill Livingstone in 2005. On March 23rd 2006 the American Botanical Council announced that it was awarding the book the first James A. Duke Botanical Literature Award. In their press release the ABC states: The Essential Guide to Herbal Safety provides a rational and well-referenced approach to determining the relative safety of many of the botanicals in the marketplace and how these herbs can be used responsibly by consumers. As such this book meets a compelling need of health professionals, is an excellent resource for those in the herb and dietary supplement industry, and provides an important public service to the consumer. There were numerous excellent books published in 2005 that were contenders for this award, but The Essential Guide to Herb Safety contained the scholarship, the scope, and the relevant applications to the needs of the herb community to merit this award.


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