MD, PhD, FMedSci, FRSB, FRCP, FRCPEd

If you believe herbalists, the Daily Mail or similarly reliable sources, you come to the conclusion that herbal medicines are entirely safe – after all they are natural, and everything that is natural must be safe. However, there is plenty of evidence that these assumptions are not necessarily correct. In fact, herbal medicines can cause harm in diverse ways, e. g. because:

  • one or more ingredients of a plant are toxic,
  • they interact with prescribed drugs,
  • they are contaminated, for instance, with heavy metals,
  • they are adulterated with prescription drugs.

There is no shortage of evidence for any of these 4 scenarios. Here are some very recent and relevant publications:

German authors reviewed recent case reports and case series that provided evidence for herbal hepatotoxicity caused by Chinese herbal mixtures. The implicated remedies were the TCM products Ban Tu Wan, Chai Hu, Du Huo, Huang Qin, Jia Wei Xia Yao San, Jiguja, Kamishoyosan, Long Dan Xie Gan Tang, Lu Cha, Polygonum multiflorum products, Shan Chi, ‘White flood’ containing the herbal TCM Wu Zhu Yu and Qian Ceng Ta, and Xiao Chai Hu Tang. the authors concluded that stringent evaluation of the risk/benefit ratio is essential to protect traditional Chinese medicines users from health hazards including liver injury.

A recent review of Nigerian anti-diabetic herbal remedies suggested hypoglycemic effect of over 100 plants. One-third of them have been studied for their mechanism of action, while isolation of the bioactive constituent(s) has been accomplished for 23 plants. Several plants showed specific organ toxicity, mostly nephrotoxic or hepatotoxic, with direct effects on the levels of some liver function enzymes. Twenty-eight plants have been identified as in vitro modulators of P-glycoprotein and/or one or more of the cytochrome P450 enzymes, while eleven plants altered the levels of phase 2 metabolic enzymes, chiefly glutathione, with the potential to alter the pharmacokinetics of co-administered drugs

US authors published a case of a 44-year-old female who developed subacute liver injury demonstrated on a CT scan and liver biopsy within a month of using black cohosh to resolve her hot flashes. Since the patient was not taking any other drugs, they concluded that the acute liver injury was caused by the use of black cohosh. The authors concluded: we agree with the United States Pharmacopeia recommendations that a cautionary warning about hepatotoxicity should be labeled on the drug package.

Hong Kong toxicologists recently reported five cases of poisoning occurring as a result of inappropriate use of herbs in recipes or general herbal formulae acquired from books. Aconite poisoning due to overdose or inadequate processing accounted for three cases. The other two cases involved the use of herbs containing Strychnos alkaloids and Sophora alkaloids. These cases demonstrated that inappropriate use of Chinese medicine can result in major morbidity, and herbal formulae and recipes containing herbs available in general publications are not always safe.

Finally, Australian emergency doctors just published this case-report: A woman aged 34 years presented to hospital with a history of progressive shortness of breath, palpitations, decreased exercise tolerance and generalised arthralgia over the previous month. A full blood count revealed normochromic normocytic anaemia and a haemoglobin level of 66 g/L. The blood film showed basophilic stippling, prompting measurement of lead levels. Her blood lead level (BLL) was 105 µg/dL. Mercury and arsenic levels were also detected at very low levels. On further questioning, the patient reported that in the past 6 months she had ingested multiple herbal preparations supplied by an overseas Ayurvedic practitioner for enhancement of fertility. She was taking up to 12 different tablets and various pastes and powders daily. Her case was reported to public health authorities and the herbal preparations were sent for analytical testing. Analysis confirmed high levels of lead (4% w/w), mercury (12% w/w), arsenic and chromium. The lead levels were 4000 times the maximum allowable lead level in medications sold or produced in Australia. Following cessation of the herbal preparations, the patient was commenced on oral chelation therapy, iron supplementation and contraception. A 3-week course of oral DMSA (2,3-dimercaptosuccinic acid) was well tolerated; BLL was reduced to 13 µg/dL and haemoglobin increased to 99 g/L. Her symptoms improved over the subsequent 3 months and she remains hopeful about becoming pregnant.

So, how safe are herbal medicines? Unfortunately, the question is unanswerable. Some herbal medicines are quite safe, others are not. But always remember: whenever you administer a treatment you should ask yourself one absolutely crucial question: do the documented benefits outweigh the risks? There are several thousand different herbal medicines, and for less than a dozen of them can the honest answer to this question be YES.

73 Responses to How safe are herbal medicines?

  • You start this off with “If you believe herbalists, the Daily Mail or similarly reliable sources, you come to the conclusion that herbal medicines are entirely safe – after all they are natural, and everything that is natural must be safe.”

    That would certainly be a pretty weird conclusion. Those must be some outside of the box herbalists…and, is the Daily Mail the equivalent of our Fox News? (If you’re not familiar with Fox, they have the reputation for making things up, coming to quite abstract conclusions, and have an abysmally low accuracy rate regarding facts.)

    In my experience, people are much more likely to assume that all modern meds have been proven to be harmless (prescribed or over the counter) – other than the fine print adverse reactions that would never apply to them. I also hear many more stories about patients not mentioning western meds they are taking when consulting herbalists. Because westen meds are perfectly safe…why would the herbalist need to know about them?

    On the other hand, every herbalist I’ve talked to or heard about warns that medicines (herbal medicines in their case) are very potent and should not be treated lightly.

    It would seem that the safest thing to do – if you aren’t consulting a skilled professional (Ayurvedic doc, Chinese Med doc, Allopath, Naturopath, etc) with a proven track record, would be to stick with over the counter homeopathic remedies. Assuming they used a good source for the water, of course.

    • jm wrote: “I also hear many more stories about patients not mentioning western meds they are taking when consulting herbalists.”

      Is that because herbalists are not required, as a matter of routine, to ascertain what medications their customers might be taking? I note that the Code of Ethics and Practice of the UK National Institute of Medical Herbalists is quite vague on the matter:

      4. In providing care you must:
      4.1 assess any condition thoroughly, with appropriate examination and investigation

      8. You must keep accurate, comprehensive, easily understood, contemporaneous and dated case notes recording:
      • relevant medical and family history

      Ref: http://www.nimh.org.uk/wp-content/titkosuploads/2012/03/Code-of-Ethics-201111.pdf

      As contraindications and risk/benefit profiles regarding herbal medicines are little known, you have to wonder if the above requirements are deliberately worded to protect herbalists.

      • “Is that because herbalists are not required, as a matter of routine, to ascertain what medications their customers might be taking?

        Not from what I hear. Might be the case in the UK…but I would doubt it.

        • jm, you are implying that herbalists are globally required to accurately assess possible adverse interactions between herbal remedies and their patients’ pharmaceutical medications. Are most herbalists medically qualified to make such assessments? I very much doubt it.

          • Globally required? You should ask an herbalist. The ones I know are quite skilled at assessing interactions.

          • What do yo mean by “You should ask an herbalist.”? Is any herbalist going to reply along the lines: “I haven’t an f’ing clue how my herbs interact with your medication because there is insufficient scientific evidence to support my practice.”?

            Tell us, jm, which internationally recognized qualifications does a herbalist need to obtain such that they are as trustworthy and knowledgable as, say, a UK pharmacist?

            Note: Most, if not all, UK pharmacists have become acutely aware of adverse interactions between prescription medicines and herbal remedies because quackery is insidiously prevalent throughout much of the UK.

            My final question: Are you, jm, adequately medically qualified to be giving alternative medical (sCAM) advice to the public? If so, your bedside manner is deplorable (and the antitheses of the placebo effect).

          • I literally mean: you should ask an herbalist. You’re certainly free to speculate as to how they would answer your questions…but you’d get more accurate info by speaking to one. Or a few. Or many.

            Sorry to hear about the insidious prevalence of quackery throughout the UK. That must suck.

  • When will people stop calling medicine, “western medicine” anywhere people can actually afford it they will use medicine, not allopathic medicine, just medicine. Anything that actually works whatever the source would be medicine, no east west divide is required except in the mind of those who don’t really seem to understand what constitutes evidence.

    • On a blog post about herbal medicine…I think it’s relevant to differentiate between herbal prescriptions and pharmaceuticals.

        • I don’t really see much of a difference, really. Best to avoid all of them, if at all possible. Except honey, of course. A spoonful every day is fantastic. Long live the bees.

        • jm said:

          I think it’s relevant to differentiate between herbal prescriptions and pharmaceuticals.

          jm said:

          I don’t really see much of a difference, really.

          Eh?

          • Oh, you were really asking what the difference is between herbal medicines and modern pharmaceuticals? I thought you were referring to the fact that medicine is medicine…in which case I really don’t see a difference.

            I figured you knew what Edzard was referring to with “herbal medicines”. You should ask him to explain what he means.

          • No, jm, I’m asking you what you believe is the difference between them after you said it was ‘relevant to differentiate between herbal prescriptions and pharmaceuticals’.

      • No problem with distinguishing them, just don’t call it western medicine or allopathy that does nothing for clarity or accuracy.

        • What would you suggest? Referring to “medicine” could mean herbs, pharma, food…

          • Perhaps it’s more pertinent for you to explain what you mean by “western medicine” and why you feel the end to use it, or are you saying aspirin isn’t used in China?

          • Actually I think it would be more pertinant for you to give me a term that doesn’t make you all defensive. How about “moderm pharmaceuticals”, would that work for you?

            Why do I think it would be best not to use medicines of any kind? Seriously? I only use medicine when I’m injured or sick. I prefer not to be injured or sick – that would be ‘plan A’.

            Aspirin isn’t used in China? Since when? That’s ridiculous.

          • @jm
            It is good to hear that you have the sense to use (real?) medicines only when they are needed.
            We were starting to worry that perhaps your somewhat labyrinthine logic might be caused by too much medicine 😀

          • @Bjorn
            Also good to hear that you realize herbal medicines are real. (Or am I reading too much into your comment?) It’s hard to track where your Harry Potter/tooth fairy lines are drawn sometimes. I also wonder how labyrinthine logic relates to your Dadaist logic on a flow chart. 🙂

  • I find it strange to examine the seemingly minute cases of severe health complications related to herb use when we compare them to the immense amount of iatrogenic deaths attributed to pharmaceutical drugs. Evidence based medicine indeed.

    • again:
      it is about the risk/benefit profile

      • And with the vast majority of herbs found at your local health food store, the risk potential is minuscule. On the other hand, 100,000 Americans die each year from prescription drugs, an exceedingly high death rate. Perhaps that should be noted.

        • this is a blog about alternative MEDICINE, not about cooking! what could be more clear than that?

          • I’m sorry…cooking food with herbs for healing purposes is the basis of healing traditions globally….or what you would call…alternative medicine. Are you truly saying that billions of people are woefully uninformed and unsafe?

          • But I also include almost the entirety of herbs sold at classic “herbal stores” that are not seen as culinary herbs. Besides a very few isolated cases, can you cite extensive evidence of the “dangers” of most of these herbs. And then compare that to 100,000 deaths a year from pharmaceutical drugs. Huh? Why the fear mongering?

          • sorry, but you seem to not WANT to understand!
            if a herbal or other treatment has no demonstrable benefit, then even if completely it would not have a positive risk/benefit profile. I am NOT fear-mongering, but you seem to be too obstinate or daft to get it.

          • Daft? You are implying that no more than a dozen herbs are “safe.” That’s simply…ludicrous.

          • DAFT AND UNABLE TO READ

          • These are your comments.

            “So, how SAFE are herbal medicines? Unfortunately, the question is unanswerable. Some herbal medicines are quite safe, others are not. But always remember: whenever you administer a treatment you should ask yourself one absolutely crucial question: do the documented benefits outweigh the risks? There are several thousand different herbal medicines, and for less than a dozen of them can the honest answer to this question be YES.

            I have read them.

            You are clearly implying that less than 12 herbs are SAFE to take. And its….silly.

          • “…do the documented benefits outweigh the risks? There are several thousand different herbal medicines, and for less than a dozen of them can the honest answer to this question be YES.”

            IT IS VERY CLEAR THAT YOU CANNOT READ!!!

          • Again I did read…For no more than less than 12 herbs, you imply that they constitute a greater risk than benefit…ridiculous. And the title to this piece is “How safe are herbal medicines?”

            You are clearly saying that only a small number of herbs should be deemed safe…and that is…just plainly wrong.

          • Jon Nettle said:

            You are clearly saying that only a small number of herbs should be deemed safe…and that is…just plainly wrong.

            Why?

          • @Alan.

            Because it’s…silly. I just named 13 that are commonly used. Do you think we should be worried about them?

          • @Jon Nettle

            Please try to understand what Prof Ernst has already said to you.

            But perhaps you could say how the medicines regulators (eg the MHRA) define what is a medicine?

          • I have read what Ernst has said. From the top of his article…

            “If you believe herbalists, the Daily Mail or similarly reliable sources, you come to the conclusion that herbal medicines are entirely safe – after all they are natural, and everything that is natural must be safe. However, there is plenty of evidence that these assumptions are not necessarily correct. In fact, herbal medicines can cause harm in diverse ways…”

            And then at the end…

            “…do the documented benefits outweigh the risks? There are several thousand different herbal medicines, and for less than a dozen of them can the honest answer to this question be YES.”

            He is clearly saying that using herbal medicines is “risky” and unsafe except in a few small cases. He continues to say I’m daft and I cant read…but I can point to what he is actually writing. I have already posted 13 herbs just off the top of my head. I could easily post a dozen more that I am sure you would agree don’t pose any danger.

            When 100,000 people die from iatrogenic deaths due to prescription drugs every year in the States, pointing to a few extremely rare cases of herbal poisoning as proof of the “danger” of herbs is simply..fear mongering.

          • when will you stop putting words in my mouth?

          • Ok, then please let me know what you think. Do you think it’s safe to consume a wide variety of herbs?

          • Jon Nettle said:

            When 100,000 people die from iatrogenic deaths due to prescription drugs every year in the States, pointing to a few extremely rare cases of herbal poisoning as proof of the “danger” of herbs is simply..fear mongering.

            Did you not read what Prof Ernst said about risk/benefit profile?

            But, if you want to bring up the numbers of iatrogenic deaths (properly evidenced, of course), please only do so if you also detail the numbers of lives saved by conventional medicine, the number of people living longer and with a higher quality of life because of conventional medicine, the number of babies who survive birth because of conventional medicine and the number of those who are suffering less and in less pain because of conventional medicine.

            And then give the same numbers for herbal treatments.

          • Just so we don’t get off track on the 3rd leading cause of death in America (iatrogenic deaths), I’d be happy to answer your question if you’ll start with mine…

            Do you think we should be worried about the 13 herbs I mentioned? Do you think they have a greater risk than benefit profile?

          • TO ANSWER THIS QUESTION, YOU WOULD NEED TO SHOW ME EVIDENCE THAT THEY ARE EFFECTIVE

          • “Effectiveness” is quite a different question than safety. The opposite of effective is…ineffective…not risky or unsafe. If you want to make the premise that less than 12 herbs are “effective”, then make that case.

            But making the case that the vast majority of herbs constitute a “risk”… Is either very poor wording, or a needless inducement of fear.

          • and where did I claim that “the vast majority of herbs constitute a “risk”… ”
            STOP PUTTING WORDS IN MY MOUTH!

          • You use that argument a lot. It tends to read like “so what if some people die due to sloppy practice of medicine – others have been helped. Collateral damage for the greater good!”

            I’m sure that’s not what you’re saying (at least I hope not), but that’s how it reads.

            In practice I hope that MDs would assume that herbal medicines (including those used in food) are effective and factor that into treatment plans. Real world treatments don’t have the luxury of waiting for documented evidence to catch up.

          • HAVE YOU HEARD ABOUT A THING CALLED “EVIDENCE-BASED MEDICINE”?

          • Oh, there should have been an “@Alan” before that comment.

          • jm

            On the contrary. It rebuts those who ask why anyone bothers with a few injuries or deaths at the hands of quacks when there are all these problems with conventional medicine.

            As Prof Ernst, I’m sure, is tired of saying, what is important is the risk-benefit profile of any treatment; without the benefit, the risk is not worth taking.

          • “HAVE YOU HEARD ABOUT A THING CALLED “EVIDENCE-BASED MEDICINE”?”

            YES, HAVE YOU HEARD OF “ERR ON THE SIDE OF CAUTION”?

          • that’s precisely what I am advocating!
            thank you

          • @Alan
            “On the contrary. It rebuts those who ask why anyone bothers with a few injuries or deaths at the hands of quacks when there are all these problems with conventional medicine.”

            No, it really doesn’t.

          • “that’s precisely what I am advocating!”

            Apparently we have different ideas about what constitutes caution.

          • @Edzard. using your logic…since say…marjoram provides no benefit…via RCTs, then they present a risk. Do you believe marjoram is risky?

          • you are NOT using my logic:
            I do not claim that “marjoram is risky” – but I KNOW that any therapy that has no demonstrable benefit cannot have a positive risk/benefit profile.
            this is obviously too difficult for you to comprehend. I will therefore leave you alone with your ignorance and herewith discontinue this fruitless conversation. cheers

        • @edzard, you are the one who suggested the term benefit/risk. If you want to be clear, the say…

          Benefit/no benefit.

          That is quite clear…and we can debate that specifically.

          But you wrote benefit/risk. Stop flying from your own words. If you write a needlessly inflammatory article, then be prepared to defend it.

  • By the way…only less than a dozen can be deemed safe? Huh?

    Oregano, thyme, garlic, ginger, turmeric, mint, coriander, cumin, paprika, anise, basil, chives…and dill. Should I throw my culinary herb collection out then? Wouldn’t want to end up in the ER…

    • read my text again and consider that the dose of these herbs in medicines would be several orders of magnitude greater than for culinary purposes.

  • I did read the text. You wrote…

    “So, how safe are herbal medicines? Unfortunately, the question is unanswerable. Some herbal medicines are quite safe, others are not. But always remember: whenever you administer a treatment you should ask yourself one absolutely crucial question: do the documented benefits outweigh the risks? There are several thousand different herbal medicines, and for less than a dozen of them can the honest answer to this question be YES.”

    You didn’t mention the use of herbs in culinary preparations, one of the most common ways of employing herbs worldwide. And yes, sometimes culinary herbs are used as liberally as “therapeutic” dosages. Ae you saying I should be concerned if I liberally apply dill in my squash soup? Either you need to be more clear or it sounds a lot like fear mongering.

    • Jon Nettle, what is it that you are failing to understand? An apple a day is reasonable dietary advice (for one of our 3-5 per day of fruit and veg intake), however, this does not imply that a diet consisting of only apples is even more healthy. Sodium chloride (table and cooking salt) and potassium salts are essential dietary ingredients, but even you must be aware that an average daily intake that is too high will result in early death.

      Dosage is the key: not too much; not too little. Herbalists, on the other hand, generally display a blatant disregard for internationally agreed safe dosage levels and ensuring that their herbs are free from harmful contaminants (especially heavy metal contaminants).

      • Herbalists? Are you referring to the literally hundreds of millions of people worldwide who integrate herbs- yes ample “therapeutic” doses of herbs into their cooking for healing their family and loved ones from sickness? Are you seriously trying to say that they are all “unsafe” and “blatantly disregarding greed safe dosage levels…”?

        Me thinks there is more than a little cultural myopia going on here.

      • I don’t think Jon is referring to “an apple a day”. Using herbs medicinally, in food preparation, is a very common delivery method. Surely, MDs look at that aspect of a patient’s diet before prescribing pharmaceuticals, although there are probably hacks and quacks out there that don’t…but hopefully they are few and far between.

        Anyone that separates “food” and “medicine” should not be prescribing. Not ethically, anyway.

  • You do realize that culinary preparations involving many different types of herbs are some of the most fundamental ways of healing people throughout the world? Adding herbs to soups, congees, stock, etc…is perhaps the fundamental way of restoring health in cultures throughout the world. Are you really saying that less than a dozen herbs can be deemed “safe” or would you like to amend that?

  • ” Do you think it’s safe to consume a wide variety of herbs?”
    SHOW ME THE DATA AND I WILL GIVE YOU A RESPONSE

  • ” Do you think it’s safe to consume a wide variety of herbs?”
    SHOW ME THE DATA AND I WILL GIVE YOU A RESPONSE

  • Would the cantankerous commentators, who so dearly dispute the dangers of herbal nostrums, perhaps care to address the quality and safety issues uncovered in this highly absorbing account. It tells of how a sizeable portion of the 44 herbal products, arbitrarily obtained from US store shelves, proved to be flawed or fallacious or even both.
    Are they perhaps prepared to provide consumer advice on how to avoid buying the proverbial “cat in the sac“?

    On reading the above comments and browsing herbalists tabulations of remedial fauna, one is led to understand that most if not all common condiments have healing qualities. But the applicability of each plant to named diseases seemshighly unspecific and most of them seem to be effectively”panaceal” in nature.
    Perhaps the type of ingredient is not so important as the magical properties of the label “HERBAL”??

    Nah…
    I tend to subscribe to the understanding so well put by Daren O’Briain in a monolog about quackery:
    “We tested it all, and the stuff that worked became ‘medicine’. And the rest of it is just a nice bowl of soup and some potpourri”

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