Are you already a devotee to the latest fad diet - nutrichondria?

If you've taken to having your Sunday roast without a Yorkshire pudding, or switched semi-skimmed for soya milk in your morning tea, chances are you could be suffering from a particularly modern malady - nutrichondria.

Billed as a preoccupation with the negative aspects of one's diet - in particular, a propensity to self-diagnose food intolerances or allergies based on supposition - the phenomenon is making its presence known in supermarket aisles and on dinner tables all over Britain.

Our eating habits have never been so, well, specific. Last year, sales of "free-from" foods in the UK - gluten-free, dairy-free, joy-free, take your pick - surged by £230 million ($402 million AUD) compared with the year prior, a rise of more than 40 per cent, while one in four Brits says they or someone in their household avoid certain ingredients as part of a general healthy lifestyle.

According to DNAFit, a UK-based genetics company that provides home-testing kits, almost half of adults go further, saying they have some food intolerance or allergy, despite only 15 per cent having undertaken the requisite medical tests to confirm their suspicions. Are 21st-century bodies no longer able to handle ingredients we've eaten for millennia, or has the vogue for ditching dairy and other "triggering" foodstuffs turned us into nutrichondriacs?

To take one of the most commonly touted intolerances du jour, a quarter of the 4,000 people surveyed by DNAFit declared a sensitivity to gluten, one of the world's most heavily consumed proteins, found in wheat, rye and barley, despite having no medical diagnosis.

For Haley Wallbank, a teacher from London, eliminating gluten from her diet seemed a suitable means of tackling feelings of lethargy and poor sleep. At the age of 52, she had come across Gwyneth Paltrow's blog, Goop, and soon found herself hooked by the vision of health the actress's lifestyle seemed to afford. She bought It's All Good, Paltrow's gluten-free recipe book and, like 22 per cent of those surveyed by DNAFit who declared themselves intolerant, self-diagnosed based on a celebrity having done so."I lived on beans and gluten-free pasta, which was disgusting, but Gwyneth was a role model - her life seemed bright and wonderful, while I was sluggish and unmotivated," Wallbank, now 57, recalls.

Having cut out the foods suggested, Wallbank could scarcely feel the effects, let alone benefits, of her new ultra-strict lifestyle. And yet she persisted: "It was like waiting for a bus that never came," she says, "even though I wasn't getting where I wanted right then, I kept thinking I'd feel better next week or month."

She hadn't realised how prevalent gluten was in foods from sauces to sausages, and how much label-reading and menu-checking her new lifestyle would require - eroding much of her social life in the process.

"It was very sudden, as far as my friends and family were concerned, and eventually they got fed up and stopped inviting me out," she remembers. "I got very isolated with it, but at the time, I couldn't see what the problem was. I was too immersed to see logic."

Wallbank believes that, while she ended up being "obsessive and unhealthy" in her dietary choices, they were driven by genuine concern: her mother had suffered from bowel cancer, and the symptoms she was experiencing were too palpable to go unaddressed. Eventually, she did consult a doctor and, on realising that she was going through menopause, reintroduced the foods she had long deprived herself of, with no adverse effect.

Wallbank believes that celebrities must be conscious of the enormous platform from which they broadcast potentially harmful notions about diet to the masses. Dairy, for instance, is an increasingly common culinary excision, avoided by the likes of Victoria Beckham and David Cameron; but while one in five believe they are allergic or intolerant to cow's milk, according to Food Standards Authority figures, only five per cent of people of northern European descent actually are.

Yet in a world where Instagram posts highlighting the latest fad diet can be seen - and acted upon - by millions in milliseconds, an A-list seal of approval for ditching foodstuffs is more persuasive for many than medical evidence. This was the case for Hannah Caldwell, 25, who as a student found herself being swept up by singer Miley Cyrus's enthusiasm for excluding dairy, meat and gluten from her diet.

"I wasn't impressionable," the events manager contends, "but when you're young, you take control over your diet for the first time; and gluten-heavy foods did make me feel really bloated." Speaking to a housemate who had coeliac disease - not to be confused with an intolerance, as the briefest exposure to gluten could trigger a powerful autoimmune reaction - convinced Caldwell that eradicating bread and pasta from her diet was for the best.

It also set her back financially - gluten-free products are up to four times more expensive than their standard counterparts - but "I felt better in myself," she recalls.

She did not undertake allergy tests, but even those who do may not find the answers they seek. "There are food allergies, sensitivities and intolerances, and they're not all the same thing," explains Dr Rangan Chatterjee, a GP and the author of The Four Pillar Plan. An allergy is an immune system reaction to a particular food mistakenly perceived by the body as a threat. A sensitivity or intolerance causes digestive difficulties - diarrhoea, bloating or stomach cramps - but no allergic reaction, and is never life-threatening.

Numerous home allergy tests have entered the market, but these can often rely on dubious methods such as hair samples or grip strength. Blood tests undertaken and analysed by medical professionals should always be first port of call.

The main disconnect comes, says Dr Chatterjee, when people test negatively for food allergies - yet still feel better for removing certain foods from their diet. "There aren't many good tests for sensitivity, and a lot of people suffering with complaints don't feel they are getting satisfactory explanations from their doctors," he says. "It's easy to denigrate people for eliminating food groups, but if cutting something out makes you feel better, I fully understand why people do it."

Dr Chatterjee recommends that, if you are planning to stop eating certain foods, doing so on a trial basis is the safest bet. Though he concedes that elimination diets "can be done to extremes", the far greater issue, he believes, is that "our microbiomes have been decimated by modern living. The bulk of the problems I see are from people eating diets that are harming their health," with highly processed culinary fare being chief among the culprits.

Even so, the issue of intolerance versus intolerants - those who cut out foods for genuine health benefits, and those restricting their diet because a social media influencer suggests they should - abounds.

As our mealtime options grow evermore diverse, whether it is consumers or manufacturers who are the main beneficiaries of this exorbitant choice, remains to be seen.

The Sunday Telegraph UK