Since 1990 the use of herbal medicines in the developed world has increased by almost 400% . Why are these products so alluring? And are they safe?

Over the past two centuries, scientific research has sought to replace the piecemeal folk-wisdom of earlier ages with the light of order, meaning, rigour and progress - with great success. Life expectancy has leapt up by decades. Many once-terminal diseases are now curable, and others have been eliminated completely. Pain and suffering, though still all too common, are alleviated immeasurably by the ever-improving fruits of scientific labours.

And yet the past ten or so years have seen the emergence of an apparently insatiable market in the western world for all things 'natural', folkloric, traditional, and, above all, non-scientific. The result has been that science-based medicine, with its emphasis on controlled study, proof, evidence, statistical significance and safety is being rejected in favour of 'alternative medicine' - an atavistic portmanteau of anecdote, hearsay, rumour and hokum.

Probably the most commercially successful and widely used branch of alternative or complementary medicine is 'phytotherapy'. These are the tablets, powders and elixirs, otherwise known as herbal medicine, that are sold in most countries, through health shops and pharmacies as 'nutritional supplements'.

Phytotherapy - the use of which has increased by almost 400% this decade - involves whole-plant preparations such as raspberry-leaf tea (Rubus idaeus) or extract of horse-chestnut seed (Aeschlus hippocastanium), which are believed, through the (scantily supported) process of 'synergy' to be more effective than the sum of their parts. It is this emphasis on whole-plant material, rather than individual chemical ingredients, that differentiates phytotherapy from the appropriation and synthetic manufacture by mainstream medicine of the active compounds of plants.

We now think of aspirin as totally synthetic, but it was originally derived, a century ago, from the bark of willow trees (Salix alba). This trend continues. Chemists have now produced synthetic versions of paclitaxel [taxol], a drug originally derived from a species of yew tree (Taxus) and extremely effective against ovarian cancer: and in the 7 May issue of the journal Science, Bei Zhang of Merck Research Laboratories in Rahway, New Jersey and colleagues show how a compound extracted from a tropical fungus might, one day be used as a substitute for insulin.

The herbal medicine market has grown by 400% this decade. In the next ten years it is expected to be worth 12-15 billion dollars a year woldwide. Allready Americans spend nearly two billion dollars every year on phytotherapy and Europeans (especially German and French people) are not far behind. In some countries these treatments are bought by more than half the population with the result that a third of all over-the-counter health products are herbal medicines.

Only a tiny minority of these remedies have been shown to have mild-to moderately beneficial health effects. For instance, St John's Wort (Hypericum perforatum), for which the NIH [US National Institutes of Health] recently funded a controlled trial, is in some people, as effective a treatment for depression and Seasonal Affective Disorder as many synthetic anti-depressants. There is good evidence that extracts of the ginkgo tree (Ginkgo biloba) boosts short-term memory in elderly patients; and another plant, saw palmetto (Serenoa repens), seems to have a shrinking effect on enlarged prostate glands.

But the dearth of research is hardly surprising when, even in its absence, manufacturers can barely keep pace with demand. Patenting opportunities are minimal. And sales regulations so lax compared with those that must be met for fully-fledged 'drug' status as to create a wide-open pharmaceutical back door. Thus there is little to motivate this multi-billion dollar industry into carrying out expensive, lengthy, properly controlled, large-scale clinical trials.

So why are affluent, otherwise rational, highly educated people (for this is the average user profile) so hungry for phytotherapy?

One theory is that the consumer/patient is disillusioned. She (I use 'she' since women in their 30's and 40's are the biggest consumers of herbal products) is dismayed at the number of questions for which science still has no answers. She has been disenfranchised by over-stretched and impersonal health services within which the individual is treated hastily and with ever-lessening humanity. But most importantly, she has become used to choice and the power to exercise that choice - or at least the illusion of these things.

Another important factor is that, as [Dr] Elizabeth Williams, editor of the journal Phytotherapy Research based at the University of London, UK, explains, "people still believe that 'natural' equals good and safe despite plenty of evidence to the contrary." This view is echoed by most researchers caught up in this unexpected anti-science boom. "People seem to manage to hold contradictory views at the same time - for example, that nicotine is bad but other natural products are good," Williams goes on. "Although they know that there are poisonous plants, this does not seem to impinge on their belief that herbs are good." This situation may stem from the fact, Williams proposes, that herbs are associated with healthy eating and good cooking.

Which is a laughable notion given that, as far as the human body is concerned, 'natural' is meaningless. Physiologically, the body cannot tell the difference between chemically synthesised vitamin C, say, and Vitamin C that has been extracted from an orange. And, yes, using garlic (Allium sativum), ginger (Zingiber officinale) or ginseng (Panax ginseng or P. quinquefolius) in cooking is indeed, 'natural' but what's so natural about consuming the equivalent of several hundred or thousand times that amount in one go, as one does when taking some extract tablets?

Equally, what's so safe about consuming substances that need meet no standards of contents? For example, some so-called 'ginseng tablets' were recently found to contain no ginseng at all. There need be no uniformity of chemical constituents: some 'St John's Wort' preparations contain totally different ingredients. In addition, so-called 'natural' remedies are sold with very little information about their claims, effects and dangers.

Another reason given for the resurgence of phytotherapy is that people are apprehensive about the side-effects associated with synthetic drugs. When compared to some of the harsh treatments that are necessary for many life-threatening illnesses, "the claim is that herbal remedies are milder, gentler and safer," explains Edzard Ernst, Professor of Complementary Medicine at Exeter University, UK.

Since years of use have seen to it that extremely toxic plants such as deadly nightshade (Belladonna) have long since been weeded out of the folk medicine cabinet, this claim may, in part, be true. Although others argue that, for the very same reasons, what is left in the ethno-pharmacopoeia is of minimal efficacy and mainly of relevance to minor, self-limiting conditions such as nausea or headaches. More worrying, however is the recent realisation - as confirmed by a paper published in the British Journal of Clinical Pharmacology last year - that, for a number of reasons, the immediate side effects of alternative medicines are grossly underreported.

The final motivation for the phytotherapy fad seems to be, as with many other branches of complementary medicine, the appeal of self-medication. In an age of choice, empowerment, convenience, and the erosion of unquestioned authority people are eager to decide for themselves what they put into their bodies (as evinced by the recent fuss about genetically modified [GM] foods). Somehow, people who would not dream of putting their hair, houses or cars in anything but expert hands feel qualified to negotiate the exquisitely complex chemistry, physics and biology of the human body.

Worse still, many of those who take herbal supplements are reticent about them when consulting their conventional medical practitioners. Indeed, communication between the two schools is thoroughly inadequate. "Interactions - especially long term interactions - with prescribed drugs are probably the sleeping giant," says Ernst on the subject of the safety of phytotherapy. "We know that interactions are a reality, but we have not even begun to study this systematically with any degree of rigour"

Herbal medicines, then, are still, as they have always been, a rich source of drug 'leads'. In fact only last week a paper in the new journal Nature Cell Biology pinpointed the active component of an ancient Chinese herbal remedy for leukaemia. Nonetheless, it is imperative that the current fashion for all things 'natural' does not blind us to the fact that some phytotherapies may or may not be dangerous and some may or may not work. For without proper research and regulation this trend is nothing but nostalgia.