Herbal remedies may make you ill. Here is how to avoid the dangers

Thinking of consulting a traditional herbal practitioner? In the UK, herbalists come in numerous guises depending what tradition they belong to: Chinese herbalist, traditional European herbalist, Ayurvedic practitioner, Kampo practitioner etc. If you consult such a therapist, you should be aware of several important issues which might save you money or protect you from ill health.

Worldwide, the treatment by traditional herbal practitioners is probably the most common form of herbal medicine; it is more popular than using specific, well-tested herbs to treat specific conventionally diagnosed conditions, an approach that might best be called ‘rational phytotherapy’ and which I will come to in a minute.

Traditional herbalists often use their very own diagnostic methods (think, for instance, of ‘tongue and pulse diagnoses’ used by Chinese herbalists) and reject or are untrained in conventional diagnostic methods. The traditional diagnostic techniques of herbalists have either not been validated at all or they have been tested and found to be not valid.

Traditional herbalists often do not recognise conventional disease categories. Instead they arrive at a diagnosis according to their specific philosophy which has no grounding in reality, for instance, energy imbalance in traditional Chinese herbalism.

Traditional herbalists individualise their treatments. This means that 10 patients suffering from depression, for instance, might receive 10 different, tailor-made prescriptions according to their individual characteristics. And none of the 10 prescriptions might include St John’s wort, the only herbal remedy that actually is supported by reasonably sound evidence of efficacy for depression.

Typically, the prescriptions of traditional herbalists contain not one herbal ingredient, but are mixtures of many — up to 10 or 20 — herbs or herbal extracts. Considering that each of these herbs might contain a multitude of pharmacologically active molecules, what you eventually ingest is a hotchpotch of a myriad of active ingredients which are unpredictable in their actions and interactions.

Even though the efficacy of the individualised herbal approach can, of course, be tested in rigorous trials, and even though about a dozen such studies are available today, there is currently no good evidence to show that the individualised herbal mixtures prescribed by traditional herbalists are effective.

The potential of harm through these individualised herbal mixtures is considerable: the more ingredients, the higher the likelihood that one of them has toxic effects or interacts with a prescription medicine. Essentially, this means that there is no good evidence that individualised herbal treatments as used by so many herbal practitioners across the globe generate more good than harm.

Therefore, you might decide to avoid traditional herbalists altogether and go for what I called ‘rational phytotherapy’. In other words, you might opt for a commercially available herbal remedy sold in pharmacies, health food shops, or over the internet. These remedies are usually bought by consumers and then self-administered, or (less frequently) they might be prescribed/recommended/sold by a clinician such as a doctor, naturopath, chiropractor etc. Typically, they contain just one herbal extract and are used under similar assumptions as conventional medicines: one (hopefully well-tested) remedy is employed for treating a defined condition, diagnosed according to validated and generally accepted criteria — for instance, St John’s wort for depression or devil’s claw for back pain.

Today, the manufacture, promotion and sale of commercial herbal ‘dietary supplements’ has grown into a multibillion-dollar industry.

This sounds as though you are on much safer ground with ‘rational phytotherapy’ compared to traditional herbalism. This may well be true; nevertheless, a few issues are worth remembering.

Some people claim that phytotherapy is effective because many of our modern drugs are based on plants. The latter part of this claim is true, of course, but this does not necessarily mean that herbal remedies are effective. The drugs derived from plants contain one single, well-defined, extensively researched molecule (by definition, this makes them conventional drugs and not herbal remedies), while herbal remedies are based on entire (parts of) plants; thus they contain (as already mentioned) a multitude of pharmacologically active molecules. This means that it is often difficult or even impossible to tell what dose of which ingredient is being administered and what pharmacological actions can be expected. In a word, phytotherapy is exceedingly messy pharmacology.

National regulations differ greatly, of course, but generally speaking herbal remedies do not have to be supported by strong evidence for efficacy. This means that a given remedy might or might not have been tested in clinical trials to determine whether it works for the condition advertised. In fact, only very few (less than 30, I estimate) herbal remedies are supported by sound evidence for efficacy, while thousands do not meet this criterion.

The widespread notion that herbal remedies are natural and therefore safe is a fallacy. Because plants contain many chemicals which can have pharmacological activity, they might be therapeutic. But they might also be toxic; historically, the most powerful poisons originated from the plant kingdom. Anyone using the ‘natural = safe fallacy’ urgently needs reminding of hemlock or poison ivy.

In addition to potential toxicity of a herbal ingredient, there are other important safety issues to consider. Most importantly, herbal remedies can interact with prescribed medicines. For instance, St John’s wort, one of the best-studied herbal remedies in this respect, powerfully interacts with about 50 per cent of all prescription drugs. It lowers their level in the blood which means that a patient on anti-coagulants, for instance, would lose her protection from a (potentially fatal) blood clot.

In many countries the regulation of herbal remedies is so lax that there is no guarantee a herbal remedy sold legally is safe. The regulators are only allowed to intervene once there are reports of adverse effects. This means that the burden of proof of safety is effectively reversed which obviously exposes consumers to incalculable risks.

The quality of the herbal product is equally poorly regulated in most countries, and this might be an issue particularly for those customers who buy on the internet. A plethora of US investigations has shown that the dose of the herbal ingredient printed on the label of a commercial product can range virtually from zero to 100 per cent. Similarly, there are few safeguards that the ingredients listed on the label correspond to the ones in the preparation. In essence, this means that it is worth purchasing not just well-researched herbal remedies but also those marketed by high-quality manufacturers via respectable outlets.

Any regulation of herbal remedies, even the European one that is often praised as protecting consumers adequately, is null and void once consumers go on the internet and purchase their herbal remedies from one of the many dubious sources found there in truly alarming profusion. Bogus claims, inferior quality and even outright dangerous products abound, and it is often impossible to tell the acceptable from the fraudulent product.

Despite all this, many consumers would argue that herbal medicines are preferable to conventional drugs, not least because the former are much safer than the latter. This may well be true but it is also largely irrelevant. The value of a therapy is not determined by its risks in isolation but by the balance between the potential harm and the known benefits. In routine healthcare we should focus on those treatments where the benefits clearly outweigh the risks. Considering all of the issues mentioned above, one might doubt whether many herbal medicines fall into this category.

Edzard Ernst, emeritus professor at the University of Exeter, is the author of A Scientist in Wonderland and the awardee of the John Maddox Prize 2015 for standing up for science. He blogs at edzardernst.com.


  • Heather Nic An Fhleisdeir

    Since it’s relevant, would you please give us your qualifications, ie: educational background to speak on phytotherapy? Where did you learn botany? Where was it that you studied biochemistry? Please also note where your phytotherapy credentials have been gained. This is important to determine if this is actually a scholarly article, since there are no footnotes from scholars or peer-reviewed journals listed as your references for the claims you have made.

    • Maria_Maclachlan

      The fact that it is written by an emeritus professor of complementary medicine should reassure you of its scholarliness but, if not, the content should. The fact that there are no footnotes is a style issue – the Spectator is a current affairs magazine, not an academic journal and, if you look carefully, you will see that Edzard links directly to the studies that support his claims. If you think his qualifications are relevant, a quick google will reveal them. I’d be interested to know what specifically in the above article you think requires a specialised knowledge of botany, if you’d care to share?

    • Andy Lewis

      One can only marvel at someone questioning the credentials of Professor Ernst when they are from the “Academy of Scottish Herbalism”.

  • Anna Newton

    It is interesting to see that you recommend buying herbs from Internet, the unregulated market full of dubious, unlicenced preparations – is that really rational phytotherapy???

    • Maria_Maclachlan

      What he says hardly amounts to a recommendation.

  • Heather Nic An Fhleisdeir

    Interesting that Hippocrates thinks otherwise: “It is far more important to know what person the disease has than what disease the person has.”

    • Ieva Zagante

      Why have you chosen Hippocrates out of the many medical men of the Ancient and the Middle ages? Only one you know? Anyway, people have learned a lot since then. First of all about causes of diseases. For example imballance of the 4 humours is proven to be false.

      • Black bile and all that yukkie nastiness, yet current fashion for prescribing

        Statins seems to reach into this territory.

  • There is one famous tradition named after the River Ganjes. Ganja. Just starting
    to become regulated in some juresdictions.