Nutritional therapists are blaming this dietary staple for everything from IBS, diabetes and arthritis to depression. Are they right? Suzanne Levy reports

Bread. For centuries it's been the main staple of our diet. Seen as the essence of goodness, no meal was complete without it. But in just a few years, there's been a major shift among health-conscious people, and for many of us wheat has become something to be avoided, shunned, a newly fashionable demon. Is it just a fad? Or is there some sense behind this behaviour?

Bread. For centuries it's been the main staple of our diet. Seen as the essence of goodness, no meal was complete without it. But in just a few years, there's been a major shift among health-conscious people, and for many of us wheat has become something to be avoided, shunned, a newly fashionable demon. Is it just a fad? Or is there some sense behind this behaviour?

There's no doubt that giving up wheat has moved from the fringes to the mainstream. The proof is in the high street. Stylish sandwich eaterie Pret a Manger has started serving open sandwiches made from wheat-free bread alongside its traditional triangles; while Sainsbury's proudly advertises its "Free From" range, 60 different products that contain no wheat, dairy or gluten, ranging from desserts to fish fingers.

Both have responded directly to their customers' changing behaviour. Sainsbury's began its new range when it found that 14 per cent of its customers follow some form of exclusion diet. And at Pret a Manger, after requests for wheat-free bread flooded in last year, management began to look seriously at the issue. Emma Blackmore, the group's development chef, says: "We have a food team who eat out all the time, who know what's kicking around. And in London, especially, it's become very fashionable to give up wheat. Our customers have shouted and we need to listen to them."

But while these food outlets see it as more than a passing trend, the jury's still out for the medical establishment as to the need for such behaviour. What all scientists agree on is that there are people who have classic allergic reactions to gluten, a constituent part of wheat, and to a lesser extent rye, barley and oats. This reaction, which can be severe, is known as coeliac disease, and now affects as many as one in 300 in the British public. It's detected in standard blood tests by measuring certain antibodies, and giving up wheat and other foods containing gluten is still considered the best form of treatment.

What is less clear-cut is the question of wheat intolerance. Many in the complementary field, and some in the mainstream, believe that this is also an immune-system response, but one that is different from coeliac disease – less intense, and slower to show itself. Symptoms may appear two days after eating bread, for example. The thinking goes that the body reacts to wheat as if it were an invader, and can set up a chain of events that interferes with the body's normal processes, causing everything from irritable bowel syndrome to thyroid disorders, arthritis, diabetes, asthma and eczema.

But where orthodox and complementary medicine really part company is on the extent to which other symptoms can be attributed to wheat intolerance. An amorphous batch of vague, "under-the-weather" symptoms is now being connected to wheat by many nutritionists and alternative practitioners – headaches, a feeling of ill health, bloating, tiredness, depression.

Exactly how (and, some would argue, if) these are linked to wheat is not yet fully understood. It's believed, for example, that intolerance could produce a mineral imbalance, causing a deficiency of magnesium, which could lead to tiredness. There's little mainstream scientific evidence to back this up, however – so doctors have been reluctant to accept these ideas.

More research would be an advantage, but that hasn't stopped nutritionists advising their patients. Dr Brian McDonogh, the first medical doctor to gain a post-graduate degree in nutritional medicine in the UK, says, "Why do I recommend giving up wheat? Because I know it works for my patients."

Neil Blair, 35, a London lawyer, is typical of the kind of people who have given up wheat recently. Feeling bloated, sluggish, "generally not on top of my game", he went to see a GP-turned-naturopath. When a wheat-intolerance test showed positive, he was recommended to give up bread and cereal. Within weeks, he lost half a stone (although he admits this could be due to exercise, which he started at the same time) and now feels lighter, and his uncomfortable stomach symptoms have disappeared. "I'm now convinced, and am preaching the cause!" he laughs.

"You have to remember that Stone Age man didn't eat wheat," points out Dr Nick Avery, a former GP who now runs the Centre for the Study of Complementary Medicine and is the consultant for Boots on homeopathy. "It was introduced only 10,000 years ago with the cultivation of crops. Which is relatively recent compared to the diet of millions of years ago, for which our bodies are better adapted – nuts, berries, fruits. We overdose on wheat and end up eating it for breakfast, lunch and dinner – toast, sandwiches, a pizza. It's too much."

Dr Avery believes that not enough is yet known of what exactly in wheat is triggering the symptoms he sees in his patients, but he is suspicious of the chemicals used to grow wheat today, as well as modern processing and the preservatives that are used in British bread-making. "My patients give up wheat and feel a lot better, then they go to Paris for a romantic weekend, eat baguettes – and say they're OK! Over there baguettes are baked fresh twice a day; here you can get a loaf that keeps for seven days in the supermarket."

These theories are still in their infancy, however, and for many in orthodox medicine the biggest sticking point is the tests used for wheat intolerance. Unlike those for allergies, there are no medically accepted tests for wheat intolerance, so unproven techniques are being used, such as electric currents on the skin.

"It's witchdoctory," dismisses Professor John Warner of the University of Southampton, who specialises in allergies in children. "There's no evidence that these tests diagnose anything at all. You need a proper test, not some crazy test which uses hair or nails sent through the post."

In his view, the only accurate way to detect an intolerance to a food such as wheat is to carry out double-blind tests in which someone is given a food, but doesn't know if it contains the substance or not. He is worried that many people are eliminating wheat from their diets without proper advice or supervision, which may mean that their diet becomes nutritionally unsound.

Dr Wendy Doyle from the British Dietetic Association views the demonisation of wheat as something of a fad. "My worry is that there are a lot of people who are wheat free who don't need to be. It's said that 20 per cent of people claim that they have intolerance, while only 2 per cent actually have it."

But given the practical difficulties of giving up wheat, it seems unlikely that people would do it without needing to – or believing that it's helping. Says wheat-free-diet devotee Neil Blair: "It's almost impossible to avoid, so I haven't gone mad, I just avoid bread and cereals. But that can be tricky. Lots of my lunches were just sandwiches – now I eat meat and salads, which is difficult in terms of expense and time."

And then there's the taste of many wheat-free products. "Pretty awful," said the Sainsbury's developers when they were testing what was available on the market. So they spent time creating products they'd want to eat, which also include dairy-free and gluten-free. Soon they'll be launching three new breakfast cereals, a white loaf and a rice-based tikka masala sauce. Clearly, for them, the wheat-free way is here to stay.