A DECADE ago, when the first season of Frasier was on TV, Niles Crane warned his brother about the many food allergies of his wife Maris.

“Just remember that she can’t have shellfish . . . poultry, red meat, saturated fats, nitrates, wheat, starch, sulphates, MSG or herring. Did I say nuts?”

“Oh, I think that’s implied,” replied Frasier.

Back in 1994 I didn’t know anyone like Maris. Now she seems to be everywhere. Organise a dinner party, and just as you are leafing through the pages of Nigella Lawson or Nigel Slater, mouth watering at the prospect, the call will come. A guest — often, but not always, a woman — will piously inform you of a food intolerance. Maybe several.

Often, this news is accompanied by the inspiring story of a life transformed through a new restrictive diet — of energy levels restored through cutting out wheat, or headaches cured by avoiding dairy products. You sigh to yourself: like it or not, everyone at your dinner table must now sample this new regime.

At children’s birthday parties it is worse. Five and six-year-olds will turn up with lists of food Mummy says they can’t have. Of course, there always were a few children who had a peanut allergy or Celiac disease, but this is something else altogether.

Once it would have been considered rather picky for a child — or an adult — to refuse so much as a Brussels sprout. These days disapproval seems to descend on those of us who eat “everything”. What, bread? White pasta? Dairy? How could you? In these times of plenty, eating everything has become synonymous with a lack of self-control — or a lack of control over one’s children.

It is surely no coincidence that Maris, with her multiple intolerances, is both rich and thin. Fussy eating — sorry, food intolerance — has become bound with issues of self-discipline, body image and social aspiration.

Around a fifth of the population now claims to suffer from a food intolerance, says the charity Allergy UK. According to the nutritionist Patrick Holford, founder of the Institute of Optimum Nutrition, surveys show that as many as 45 per cent of the population probably has a food intolerance. “It really is a huge problem. The critical thing is for people to get tested. They must then get rid of any food that they are intolerant to,” he says.

But it appears that rather than being a genuine physiological problem, for a large number of people food intolerance may be all in the mind. A new study, to be published in the journal Social Cognition next month, reveals that many dietary intolerances could amount to little more than figments of the imagination.

Psychologists at the University of California in Irvine were studying the phenomenon of false memory when they discovered that it was easy to manipulate people into thinking they had a food intolerance. When told — falsely — that a particular food had previously made them ill, many people later reported an intolerance to that food. Dr Elizabeth Loftus and her colleagues asked their subjects to answer detailed questionnaires about early eating memories. A week later they were each handed a bogus dietary profile which contained a single untruthful fact about the history of their relationship with food.

Some were told, for instance, that they had become sick when eating pickles or hard-boiled eggs. In later interviews, about 40 per cent of those who took part in the study confirmed that they clearly remembered having an adverse reaction to the food in question or believed their intolerance to it was real. Compared with a control group, those who were fed the false information also said they would avoid the offending food whenever possible. “It is called the false feedback technique, ” explains Loftus. “You gather data from subjects and can use it to lend credibility to this false profile.”

The idea that food problems can be imagined is not new. An investigation by the British Nutrition Foundation (BNF) two years ago revealed that 20 per cent of Britons think they have a problem with food, but Allergy UK confirms that only 2 to 3 per cent of people in the UK suffer from a true allergy.

Times recommends

• How I lost the gift of joy for a while
• How to get Coleen Rooney's post-baby body
• The A-Z of winter style rules