Traditional herbalism: no good evidence that it works

The evidence for treating patients with an individualised mixture of several plant extracts is patchy at best, says Professor Edzard Ernst

Herbal medicine, many GPs might believe (not least after reading my last blog), is a bit of a success story within CAM. I am afraid this is not quite true.

Many of your patients would consult a herbalist. The question is, how effective are their treatments (rather than single herbal remedies they might buy over the counter)?

Traditional herbalism has nothing to do with the fact that garlic, for example, has been shown to be effective for hyperlipidaemia. The approximately 1,000 British herbalists do not think in conventional disease categories and hold beliefs abandoned by the rest of medicine 200 years ago - a 'damp' and 'cold' condition requires a 'dry' and 'hot' remedy, for example.

The medicine prescribed by traditional herbalists would typically not be an extract of a single herb but an individualised mixture of several plant extracts. The composition of this mixture depends on the characteristics of each individual patient. Thus, ten patients with the same condition could get ten different prescriptions.

Neither the diagnostic validity nor the clinical effectiveness of this approach are well-investigated. Only a very few randomised controlled trials (RCTs) of individualised herbalism are available, and collectively these data fail to demonstrate the superiority of this approach over placebo or standard treatment.

As traditional herbalists use mixtures of multiple extract, safety issues are much more critical than in phytotherapy. The potential for toxicity, herb drug interactions, contamination, or adulteration increases in parallel with the number of plants in the mixture. These potential problems are currently not well-researched. Thus we do not really know how safe traditional herbalism is.

What follows is simple and in stark contrast to what many people seem to assume: today there is no good scientific evidence to demonstrate that traditional herbalists do more good than harm.

Professor Edzard Ernst is professor of complementary medicine at the Peninsula Medical School, University of Exeter