A couple of weeks ago, the University of Washington in Seattle published a paper saying that echinacea is no better than a placebo when it comes to treating colds in children. Now, when I see someone in the chemist reach for a pack of echinacea, I want to say to them: "Didn't you read the study? This stuff is useless. Put it back." Why do people choose to ignore the evidence of studies that refute the efficacy of their favourite alternative remedy? Is it a case of wilful ignorance?
"I think two mistakes encourage people to believe in medicines even when tests have shown that they don't work," says Jamie Whyte, the author of Bad Thoughts (Corvo). "The first is to mistake negative test results - tests that show there is no correlation between taking the medicine and getting better - for a mere absence of positive evidence that there is a correlation. That is, people that think that, after such tests, the matter simply remains open.
"The second mistake is to think that although the medicine doesn't work for everyone (that's all the negative test shows, they think), it does work for them. They've taken the medicine and got better. They don't realise they would have got better just as quickly without the medicine. You could say their mistake is in personalising the matter - the medicine works for them; tests only show what happens with other people."
Some people claim to have lost faith in science altogether, and are simply guided by their inner guru when it comes to purchasing decisions. Mike Miller, a civil servant from Limerick, Ireland and a fan of herbal remedies, says he hasn't lost faith in science, but "studies can be used to prove anything". And that certainly seems to be the case. One week margarine is good for you, the next it's not. Eggs are bad for you, then they're not. Who can keep up? In the same week that the echinacea findings were published, Trudy Norris, the president of the National Institute of Medical Herbalists, told the BBC: "This research contradicts many other studies that show the beneficial effect of taking Echinacea."
Faced with this confusion, I would opt not to buy any alternative remedies. But this is not the decision most people make when reading the results of these sorts of studies. Alternative remedy believers tend to remain loyal to their faith. They will readily quote studies that support the claims of their favourite alternative remedies, yet ignore studies that refute those claims.
Sceptics sniff at such irrational behaviour, but we're all prone to irrational behaviour at some time or another. Thinking like a scientist simply isn't in our nature. Dr Michael Shermer, the publisher of Skeptic magazine (www.skeptic.com), says that most people who turn to alternative remedies do so when traditional medicine fails to provide what they're looking for, which is attention along with a cure. "In addition," he says, "humans are pattern-seeking animals who think anecdotally, not scientifically. They think, 'My aunt Mary tried extract of seaweed and her cancer went into remission, so there must be something to it.' Most of us, most of the time, accept such stories as evidence. We have been thinking this way for millions of years, but we have been doing science for only 400 years."
But there's nothing contradictory in being a scientist and a believer in complementary medicine. Professor Edzard Ernst, a professor of complementary medicine at the University of Exeter, is both scientist and alternative medicine man.
Ernst acknowledges that it is difficult for most people, even health professionals, to make sense of apparently contradictory information. "I only see two options," he says. "First, you trust someone's advice. The trouble with this is finding someone competent. Herbalists might be overstating their point, and UK doctors usually haven't got a clue about herbal medicine. Second, you refer to sources that are based on the totality of the available evidence, like our book The Desktop Guide to Complementary and Alternative Medicine [Mosby]."
And there's an issue with the studies themselves. "The problem with herbals is that because of their traditional use, there is no possibility of patenting these products, because of 'prior art'," says Dr Liz Williamson of the School of Pharmacy at the University of London. "So there is little incentive for anyone to do these studies - and if anyone does, the competition can just use the data (which is in the scientific literature and therefore the public domain), to sell their own product. And this product may not have been tested at all, and may not even be similar, but the consumer rarely knows the difference between a quality product and a rubbish product - they just go for the price, and buy on the net."
Bear in mind that alternative remedies are not, at worst, just ineffective. Some are downright dangerous. Kava kava, a natural tranquilliser, was removed from UK health-food shops after four people died and seven needed liver transplants after using the herb.
Trudy Norris admits that there is a lot of misinformation, but says labelling requirements will improve as a result of an EU directive on traditional medicines. In the meantime, there's no simple solution to the question of whether you should use particular ones. You have to do your homework. And if avoiding questionable remedies doesn't save your life, it might just save you a few quid.
Treatments put to the test
What it is: The root of the ginseng plant is used as a mild stimulant and a tonic. It is also said to be good for treating impotence and stress.
The evidence: "There is much confusion about ginseng - not least because two different plants are often treated as though they are the same: Asian (or panax) ginseng and Siberian ginseng," says Professor Edzard Ernst. "Asian ginseng is more popular. It's used for a range of indications; as a general tonic or as an anti-diabetic herb, for instance." The evidence is promising but not convincing. He also cautions that Asian ginseng is thought to interact with prescribed drugs.
The verdict: Promising, but bear in mind that ginseng is not completely harmless.
St John's Wort
What it is: A plant that, taken as an extract, is popular as a self-prescribed treatment for mild to moderate depression. More than two million Britons use St John's Wort, one of the nation's favourite over-the-counter herbal remedies. Sales are worth £5m a year.
The evidence: "Even though several recent US trials disagreed, the evidence is still overwhelmingly in favour of St John's Wort as a treatment for mild to moderate depression," says Professor Ernst. "If you combine it with other drugs, problems can arise; it interacts powerfully with a host of prescribed drugs. So you should take it only if you don't use other medications, including oral contraceptives." Self-prescription means self-diagnosis. A trial published in the Journal of the American Medical Association showed that the herb has no more effect than a placebo when it comes to treating major depression. And while it may be a natural substance, St John's Wort should be treated with caution. People taking medication to treat depression, cancer, pain, high cholesterol, high blood-pressure and heart arrhythmia should avoid taking it. Also, it's not advisable to spend too much time in the sun if you're taking the herb, as it causes skin photosensitivity. But then, sunlight is also meant to be a cure for mild depression. And sunlight's free.
Verdict: Almost certainly helpful for mild or moderate depression. It is best to consult your GP.
Evening primrose oil
What it is: Best known as a hormone-balancing treatment for those suffering from premenstrual syndrome (PMS). It is also used to treat a range of other disorders, including dermatitis and eczema.
The evidence: Professor Ernst says that although evening primrose oil has been promoted for myriad conditions, there is no conclusive proof that it works for any of them. A study published last week found that the oil seemed to work even less well for eczema than dummy capsules. But Dr Marilyn Glenville, an expert on natural women's health, says that evening primrose oil has been shown to be more effective for PMS when taken with vitamin B6.
Verdict: This is an expensive product, but worth a try for PMS if you can afford it.
What it is: The most popular of the Bach Flower Remedies developed by Edward Bach, a homoeopath who believed sickness could be healed by treating the underlying emotions. It consists of five plants: cherry plum, clematis, impatiens, rock rose and star of Bethlehem. Meant to help relieve emotional distress.
The evidence: Bach discovered his remedies "intuitively". His method was to place flowers he'd instinctively selected in spring water and set them in the sun. Once he'd harvested the "energy" from the flowers, he'd dilute the mixture hundreds of times to make it more effective. The evidence for Bach Flowers is scanty, though many people do swear by it.
The verdict: Go ahead if it makes you feel better.
What it is: Otherwise known as "coneflower", this herbal preparation, usually available as drops, has become immensely popular as a treatment for boosting the immune system and, in particular, for preventing colds.
The evidence: A recent study by the University of Washington in Seattle showed that echinacea is no better than a placebo in treating colds in children. Echinacea has fared better in other studies, which have appeared to show that it can shorten the duration of colds. Advocates would say that the Washington study is of little relevance, as the herb should be used to boost the immune system to prevent colds, not as a remedy. However, Professor Ernst says the jury is still out on whether it has a role in cold prevention.
Verdict: there's little in the way of proof, but many swear by this. And it will do no harm.
What it is: Used as a cream or homoeopathic pills to treat bruises, aches and sprains.
The evidence: "For Arnica, there's quite a lot of pharmacological evidence (as opposed to clinical results)," says Dr Liz Williamson of the School of Pharmacy, University of London, "but it has got very confused with the homoeopathic issue." Recent and much publicised trials conducted by Professor Ernst showed Arnica, in homoeopathic pill form, to be ineffective in treating post-operative pain, bruising and swelling. Much of the press wrongly took this to mean that Arnica cream was also ineffective. This is not proven to be the case.
The verdict: Doesn't look too promising as a homoeopathic treatment, but the jury's still out on the cream version.
What they are: Live bacterial cultures said to be good for the gut, immune system and protection against infection. "Friendly" bacteria help to keep micro flora in the intestinal tract in balance.
The evidence: Studies show that probiotics may treat irritable bowel syndrome. Advocates think they can help other problems, including acne. "They're effective," says Ian Marber of the nutrition clinic The Food Doctor, "but the yoghurt drinks aren't necessarily as good as taking a capsule."
The verdict: Reasonably good evidence as a treatment for specific disorders.