Leaving the Land of Woo

A rational, sceptical look at the ideas of alternative medicine, food, religion, and the paranormal

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Is herbal medicine safe?

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Herbal medicine is often seen as one of the more reliable of the alt-med options and has an air of respectability about it.  We know of course that many plant extracts have been identified and purified and form the basis of pharmaceuticals so returning to the source seems as if it might be rational.  Herbal medicine businesses exploit this assumption.

There are claims that herbal medicine is a tried and tested solution to many common medical complaints such as skin problems, digestive disorders, high blood pressure, and a host of other conditions.  Based on the idea that plant extracts are natural, they appear to be somehow better than the processed and artificial pharmaceuticals produced by the drug companies.

Indeed, the distrust of the profit-oriented Big Pharma is high on the list of complaints from the alt-med community and encourages many to look for a low-tech more unrefined solution.  But is herbal medicine really the answer to distrust of Big Pharma?

What's in it?
This seemingly innocent question is quite difficult to answer, because the production process is uncontrolled.  Even with vitamin pills we know precisely what is in them but this isn't at all the case with herbal medicines. Every plant extract contains hundreds and possibly thousands of chemicals in different quantities.  Some of them, perhaps even most of them, will have a biological effect.  The composition of a plant extract will vary depending on which part of the plant is used and the extraction process employed.  The result will be a mixture of indeterminate content and unless the manufacturers carry out a detailed assay, they won't know the contents either.  They settle instead on making a rough list of what they think is in it - not the same as an accurate list of ingredients.

With any biologically active chemical, there will be a range of effects, some possibly beneficial and some potentially harmful.  As the concentration increases, different effects become more significant, until a toxic level is reached.  Even something as anodyne as aspirin becomes toxic in high concentrations.  So without knowing what those chemicals are, and at what levels they become toxic, we cannot say with any confidence what the effects will be.

Ayurvedic medicines and TCM (Traditional Chinese Medicine) herbal preparations are not covered by the same legislation as applies to pharmaceuticals.  That means that they can be marketed without assays to identify the composition, and without trials to test efficacy and side-effects.  Since the preparation process is not controlled, no-one can claim to know the true composition.

In practice, neither the person selling nor the person buying herbal medicines knows precisely what's in it.

Active ingredients and remedies
Traditionally, some herbal preparations are associated with helping particular conditions.  In the sixteenth century, herbal medicines provided a main source of treatments because there was no clinical practice that we would recognise today.  Some of these preparations had active ingredients which brought about some relief, but most were mixtures which had a similarly mixed effect.  Whilst they may have contained a useful active ingredient, often the effect was dampened or modified by the presence of other chemicals, some very harmful.

Frequently, the herbals were designed to produce an emetic effect, to make the patient vomit.  Others were designed to purge the bowels by providing a strong laxative effect.  Most of the herbal preparations were used for their mild poisoning effect. Such mild poisoning was seen as useful in expelling various types of "humour".  But the theory of humours was quite wrong - the human body does not work that way.  Nowadays we do not use emetics and laxatives to purge patients, bleeding or sweating them to remove choleric humour.   We don't use tobacco and arsenic to treat bubonic plague - we can use a simple effective antibiotic called tetracycline. 

The use of Herbals such as Culpeper's Complete Herbal involved mixing magical spells with religious verses, astrological predictions and charms along with the herbal preparations.  They also contain questionable advice as for example in describing the taste of rhubarb leaves: "a fine tart or sourish taste, much more pleasant than the garden or wood sorrel".  Rhubarb leaves contain oxalates which are seriously poisonous and they should not be eaten.  These herbals belong to a pre-scientific world where even basic knowledge of human biology was lacking.  These remedies mostly didn't work, but it was all the physicians of the time had available to them.  We now have so much more knowledge.

Can we trust old remedies?
An intelligent reading of an old herbal will startle the reader with its patently wrong notions about biology and health.  We know much better now how the human body works and we can identify chemicals which affect the body's chemistry.  Relying on the recommendations of books of herbs from long ago is in fact ignoring the overwhelming body of clinical knowledge we have since acquired.  That body of scientific knowledge is not at all invalidated by any of the activities of Big Pharma and it is a mistake to throw out the clinical science baby with the Big Pharma bath water.

Old herbals are full of misinformation, wrong advice, patently absurd recommendations.  They are historical curiousities which tell us how people hundreds of years ago thought the human body worked.  They were largely wrong and following their advice will also be wrong.

Some herbal extracts contain pharmacologically active ingredients which can help us.  For example, the chinchona bark contains quinine which, when extracted and purified, is a powerful treatment for malaria.  Boiled up rhubarb leaves on the other hand is poisonous.  We need to be able to separate out the safe and useful plant extracts from the rest of the chemicals we get when we mash up plants.

Surely they must work if people use them?
That's a wonderfully alluring but quite incorrect assumption.  Many people buy these remedies, take them, and the condition they were supposed to treat then simply goes away on its own as it would have without treatment.  Many mild skin conditions and digestive disorders are of this type.  Often the herbal preparations do nothing at all but the sale has already been made.  To find out if there is any effect, we need to trial them under controlled conditions.

Countless trials have been made of various plant extracts and the results are only significant in a very small number of cases, cases in which the active ingredient is already known and often available as a clinically tested pharmaceutical preparation.  Despite massive investment in advertising from the herbal medicines industry, the quality of data from trials of efficacy is uniformly very poor.  The evidence of efficacy is just not there for the vast majority of cases trialled.  PubMed is a useful source of trial data and the link is listed on this site.

Dangerous preparations
Some cases have been reported in the press of adulterated herbal medicines, preparations that contain harmful levels of lead and mercury, and some TCM preparations which contain serious poisons such as aristolochic acid.  Without an adequate process of control and assay, these products should carry a health warning.

Apart from the quality control in the products themselves, there is grave concern about the diagnostic skills of those dispensing such medicines.  If someone assesses illness in terms of concepts that were invalidated more than three hundred years ago, we would understandably suspect the accuracy of the diagnosis.  In TCM, diagnosis is made using fictitious ideas of how the human body works, without any basis in fact.  TCM practitioners therefore have no credible means of diagnosing illness, far less prescribing a particular suitable medication.

  • Traditional or natural does not mean the same as effective
  • Non-commercial doesn't necessarily mean safe
  • Herbal medicines are commercial products just like drugs
  • Herbal medicines have unknown composition
  • Herbal medicines have no dosage control
  • Medical practitioners have to have demonstrable diagnostic skills which herbal medicine sellers lack
  • Traditional Herbal references are full of incorrect and potentially dangerous recommendations
Last Updated on Wednesday, 26 January 2011 13:22