The Human Condition: The wonder drugs that grow on trees

Mind-altering drugs - the responsible ones you get from your GP, not the dangerous ones supplied by your local pusher - are under attack. Not from self-righteous moralists, but from a far more ancient source of comfort. Herbs and natural foodstuffs, long relegated to the medical fringe by the wizardry of modern chemistry, are emerging to challenge synthetic drugs in a battle for the mind.

The latest contender is something called PS - short for phosphatidy- lserine - a type of fat derived from soya beans that promises to restore flagging memory, improve concentration and banish anxiety. At the recent launch, journalists were bombarded with scientific evidence of its effectiveness - 42 studies, 17 double-blinded - plus pictures of brain scans of a woman sunk in gloom and dementia. The "before" version shows her brain as dark as a deserted warehouse, but after taking PS, her scan looks like Christmas Eve in Oxford Street, all lit up, with brain cells buzzing.

Now, this is the sort of stuff we expect from big-spending pharmaceutical companies - studies, statistics, hi-tech pictures - but it's a relatively new tack for natural products, seen as not only lacking financial muscle but also as being more homey.

PS, we were told, was a natural lipid "essential for the normal functioning of every cell in the body". Anyone whose internal stocks had been depleted by ageing or unhealthy living could benefit from a top-up. In fact, there was even a syndrome it could treat, known as Age Related Cognitive Decline (ARCD). How could we tell if we had it? "Higher mental tasks that were previously easy to do," explained cell biologist Dr Parris Kidd, "such as memorising a telephone number or shopping list - all get harder." Not only could ARCD slow down your life, but it increases your chances of getting dementia. Obviously, we all need PS.

This is playing the drug companies at their own game, but these new kids on the block have an ace up their sleeves. We have become sceptical about synthetic drug claims because they always have unwanted side effects. Something that is natural and, in the case of herbs, that has been used for centuries, seems safer. We just need convincing that they actually work.

The first to pull off this combination in the mass market was St John's Wort, launched in Britain earlier this year. A rather insignificant looking weed with yellow flowers, which has been used for generations by herbalists to treat mental problems, an extract of its leaves massively out-sells Prozac in Germany as an anti-depressant. Again it was accompanied by an impressive array of double-blind trials showing that it was as good as the chemical "serotonin re-uptake inhibitors", with fewer side effects. No wonder sales have taken off here, too.

Herbalists have often complained that their safe and effective treatments were being ignored because, without the possibility of a patent, no-one would pick up the tab for expensive clinical trials, necessary to convince doctors. But now, the sheer potential of the market is powering this new policy, led largely by German firms.

For, while the market for antidepressants is big, many observers think the jackpot for the next century will be a safe and effective treatment for memory loss and the terrible mental decline brought on by Alzheimer's. Already the disease affects 800,000 people in Britain and the numbers are set to double in 20 years.

This is the market PS is aimed at, as well as the fiftysomethings who want to keep themselves sharper in today's competitive climate. But already it has a high-profile rival in Ginkgo biloba, a herb, in the form of a tree, whose leaves, it is claimed, can enhance memory by improving the flow of blood to the brain.

Ginkgo biloba has been used in China for 5,000 years and was already an ancient species when the dinosaurs became extinct. Once again, it is backed up by an impressive array of statistics - pounds 5 million invested in research, 70 scientific papers testing its claims to reduce blood clotting, encourage blood supply to the brain and scavenge dangerous free radicals. And again the trials against the main synthetic "cerebral vasodilator" in which it performed just as well. "Ginkgo biloba appears capable of improving cognitive performance and social function of demented patients," concluded a study published in the reputable Journal of the American Medical Association last month.

Inevitably, the claims of both Ginkgo and PS are disputed. It has been pointed out that PS is not completely identical to the lipids found in all our brain cells, while a scientific supporter of PS claims that various of the Ginkgo trials were not properly conducted and that others were not as rigorous as those done on PS. But such sniping is a sign that herbs and supplements are on the offensive and that they have moved into the arena of scientific debate. It is a trend that can only grow.

"There are all sorts of other plant products that have not been studied scientifically because no-one has been prepared to put the money up," says Dr Peter Houghton, lecturer in pharmacology at King's College, London. "However, that seems to be changing." For example, his lab is currently looking at Sage, which he believes may turn out to be effective in treating Alzheimer's. "We've found there is something in it that binds to cells in the brain affected by the disease, so it may provide some protection," he continues. "It also has anti-inflammatory properties and it is one of the plants that contains oestrogen-like chemicals which protect against Alzheimer's, too." But before you start pigging out on sage and onions, it is worth knowing you need about 100 grams of the stuff.

Some of the other plants that look promising in the memory field include laburnum and daffodil bulbs. One of the surprises is that Rosemary, traditionally used by the Ancient Greeks as a memory booster used by the Ancient Greeks, doesn't seem to have any effect.

This shift from synthetic to natural mind control substances can be seen as part of the same tide of consumer choice that is driving companies to become more eco-friendly. But it has another intriguing implication. If it is all right for people to buy herbs over the counter with the express intention of cheering themselves up or improving a medical condition, why can't they do the same with marijuana?