It may not be the elixir of eternal youth, but of all the hyped superdrugs of recent years, DHEA looks the best bet

If you haven't heard of it yet you soon will. DHEA - the latest anti-ageing, anti-Alzheimer's, anti-cancer, anti-fat, anti-everything- awful wonder drug - is on its way to Britain from America, where it is selling to health freaks like fat-free hot cakes.

It comes in the slipstream of melatonin, CQ10, ginkgo biloba, growth hormone, echinacea and bushels of other "natural" panaceas. None of these - curiously - seems to have stopped people from getting old, doddery and forgetful, despite relieving them of more than pounds 60m each year. So is DHEA any different?

Actually, it just might be. DHEA (full name dehydropiandrosterone) is a steroid hormone produced naturally by the adrenal glands. Although levels made by the body are abundant in youth, they drop dramatically with age: by the time a man is 70 he will be making less than 10 per cent of the DHEA he had at his physical and sexual peak and the difference is even more marked in women. A synthetic form of DHEA, dubbed the "fountain of youth" in the hype, is now taken as a dietary supplement by hundreds of thousands of health-conscious Americans and is fast becoming the latest medical elixir: converts claim that it can reverse ageing, restore sexual vigour and prevent cancer and heart disease.

The difference between DHEA and many other unlicensed wonder drugs, however, is that it comes with an impressive scientific track record. More than 2,000 studies suggest that it may have wide-ranging beneficial effects, and the scientists who are working on it seem unusually willing to try a taste of their own medicine. At a recent international conference on the subject, one in four delegates admitted they took DHEA supplements themselves.

One of the scientists researching DHEA is Dr Joe Herbert of the Centre for Brain Repair at Cambridge University. "DHEA is a different kettle of fish from melatonin - most of the claims about that were rubbish," he says. "It is too early to prove that DHEA can have significant effects, but the evidence so far is looking good. If I were a betting man I'd be taking it myself."

Dr John Moran, of the Optimal Health Clinic in Harley Street, who specialises in ailments of middle age, already does. "I have been on it for a year now and I am leaner, fitter and have a far better sense of general well- being," he claims.

He also gives DHEA to some of his patients.

"I use it for middle-aged men and women who complain of depression, anxiety, stress, fatigue, or memory and concentration problems." Nearly all of them subsequently report increased energy and generally improved health, he says, although he admits: "It is difficult to isolate the effect of DHEA because it works synergistically with the other hormones.

"I find it particularly useful for women who complain of lack of libido because it converts in the body to testosterone, and it is this which creates sex drive in both women and men. You have to get the levels of all these hormones right, though. I try to tailor the supplements so the entire hormone profile of my patients is closer to how it was when they were young."

Called the "mother of hormones", DHEA is thought to provide a reservoir of biological building material on which the body draws to keep all the other hormones - particularly oestrogen and testosterone - at optimal levels. Animal studies (and a few trials on humans) suggest that it can help to clear the arteries of the fatty gunge that causes cardiovascular disease; "buffer" brain cells against the destructive effect of the stress hormone cortisol and boost serotonin levels, preventing depression; help to burn up sugar, encouraging weight loss, and that it may protect against breast cancer in the same way as the drug tamoxifen - by attaching to oestrogen receptors and blocking the effect of natural oestrogen on hormone- responsive tumours. One study showed that when older, slower mice were given the hormone they became more active and learnt to run mazes as easily as younger rodents.

However, Dr Herbert points out: "You can't rely on animal studies because rats and mice don't make DHEA like we do so the effect on them of supplements may be different. What we need to do is to give DHEA to a lot of people for a long time under controlled conditions. Until we have done that we can't say anything about it for certain." Dr Herbert himself is currently running a trial of DHEA as a treatment for depression. The result is not yet known but in America three carefully controlled trials on middle-aged human volunteers have returned particularly interesting results. One showed that DHEA supplements raised the number of tumour and infection-fighting immune cells. It also increased sensitivity to insulin and therefore may have a role in staving off diabetes. Another revealed that it increased muscle and reduced fat - a fact already known, and used, by a number of athletes. In a second trial, 82 per cent of post- menopausal women given DHEA said that it made them feel more energetic, healthier and generally younger.

Overall, the studies so far make an impressive case for DHEA, but not a conclusive one. Professor Tom Kirkwood of Manchester University, an expert on the molecular basis of ageing, is cautious. "DHEA is interesting - it clearly affects the signals which pass between cells and that could in turn affect the way our organs function, so it could have implications for health in general. But the fundamental process of ageing goes on inside individual cells and I can't see any way that DHEA could alter that."

What of the safety of DHEA? Very few adverse effects were reported by volunteers in the published trials and Dr Moran says that he has seen none among the hundreds of people he has treated. However, they were all middle-aged people on a moderate dose (usually 50mg a day). In larger doses, or if used by younger people, there is a risk that DHEA could push up sex hormone levels to the point when women might start to grow facial hair and men to grow breasts. And although DHEA seems - on the face of it - to give protection from breast cancer to post-menopausal women, there is a theoretical risk that long-term use could stimulate hormone-sensitive cancers such as those of the womb, the ovary, the prostate and - paradoxically - the breast.

"It is like the Pill and HRT," says Joe Herbert. "It may be years and years before we will know what the full range of effects are. For that reason we have to advise caution - people shouldn't just rush out and buy it until we have done much, much more research over many years."

In fact you can't just rush out and buy it, anyway - not unless you can surf the Internet or have the patience to plough through the Yellow Pages in search of illicit supplies. The Medicines Control Agency - unlike its US equivalent, the FDA - takes the view that DHEA, like melatonin, is a medicine rather than a food supplement and, as such, cannot be legally sold except by private prescription from a doctor "on his or her personal responsibility".

A phone around health stores last week, however, found two who said that they could get DHEA on order and one that got around the restriction by selling another hormone called pregnolenone, which they claim is turned into DHEA in the body and works just as well as the real thing. The Hale Clinic in Regent's Park - the UK mecca for serious supplements junkies - said that they sold DHEA on private prescription. High street stores such as Holland and Barrett do not stock it.

On the Internet, though, the story is different: a few clicks and you get a list of dozens of mail-order suppliers, some with price lists (a month's supply costs about pounds 25). "The fountain of youth in a bottle," says one. "At last - the antidote to ageing," claims another.

"I would advise anyone thinking of buying through these suppliers to be very, very careful," warns Herbert. "Some of the stuff advertised on the Internet may not be DHEA at all - and unless it is pure it could be dangerous. It also has to be in microcrystalline form or it won't be absorbed.

"There are a lot of cowboys in the supplements business and a lot of nonsense talked. I have a hunch that DHEA may turn out to be very useful. But it is not the elixir of youth, and anyone who says it is, is talking hype. Don't fall for it"n