In a sun-filled café in Sydney's Annandale, Kelly Hender pulls two slices of bread from her handbag and hands them to the waiter. Across the small table, her breakfast companion rolls her eyes, jokingly.

Moments earlier, Kelly, 30, had inspected the list of ingredients of the café's gluten-free bread. "I'm sorry," the pretty blonde explains with a smile, "but I can't actually eat yeast, either. Could you use this for my toast, instead?" Apprehension flashes across the waiter's face, but he disappears into the kitchen. Suddenly, Kelly hears muffled shouting and the red-faced waiter reappears.

"I'm so sorry, but the chef says there's no way he's taking this bread," says the waiter apologetically. "The chef is sick to death of everyone coming in here saying they can't eat this and they can't eat that."

One evening, across the city, 23-year-old public relations officer Kate Alexander is sitting in her Lane Cove living room punching in the number of her favourite pizza place. The usually simple task is more complicated for Kate, whose naturopath diagnosed her in mid 2007 with intolerances to not only wheat and gluten (a protein found in wheat, rye and barley), but also lactose (a sugar found in notably in milk), oranges, capsicum, coconut, cashews, peanuts, yeast, sugar and blueberries.

"I try to make a joke out of it," she says. "I say, 'hi, it's bubble girl here. I'd like the vegetarian pizza on a gluten-free base, hold the cheese, the capsicum, the mushrooms and the nuts'.

Fortunately, her local pizza place is perfectly happy to accommodate her specific food. "So many places are starting to cater for people like me - [it] just goes to show that there are a lot of people dealing with a similar issue."

In fact, according to dietitian Sue Shepherd, who specialises in the area, up to one in four people, mostly women, now claim to have a food intolerance, making this nutritional trend the "cultural phenomenon of the millennium" - and one of the hottest food movements for 2009, according to the American Culinary Federation.

But while many intolerances and allergies cause crippling symptoms, requests for wheat-free, gluten-free, dairy-free, yeast-free, preservative-free foods are becoming ubiquitous. And they are causing problems. For every tolerant pizza parlour, willing to accommodate the dietary requirements of women like Kate, there's an exasperated and overworked chef - as Kelly's experience demonstrated. Perhaps many of them might be more understanding if they didn't harbour a sneaking suspicion that "food intolerance" was simply shorthand for "diet" or "fussy eater".

A food intolerance is an inability to process food and is distinct from an allergy, where the body attacks the food as a toxin, causing a much more serious reaction. An allergic reaction to peanuts, for example, can result in vomiting, diarrhoea or even a potentially fatal anaphylactic fit. A food intolerance can also cause a nightmarish litany of symptoms - anxiety, crippling diarrhoea, palpitations, rashes, hives and swelling, moodiness and fatigue, nausea or stomach pains, bloating, migraines - but sufferers often elicit far less sympathy.

This skepticism isn't wholly unfounded. Experts agree that while there has been a genuine increase in the number of people with intolerances or allergies, there is concern that many people diagnose themselves without ever seeing a doctor or dietitian. Cutting out entire food groups can lead to malnourishment, and can even mask an eating disorder.

Others are worried that for some, restrictive "free-from" food intolerance diets are symptomatic of society's obsession with healthy eating - or simply provide the perfect excuse for those on the lookout for a socially acceptable post-Atkins reason to avoid bread and pasta.

After all, when super-svelte Victoria Beckham calls pasta her "kryptonite" and style icon Carrie Bradshaw feigns a severe reaction to parsley, the question is inevitable: how much is fact and how much is fashion?

The experts weigh in on food intolerances in the July issue of marie claire.

Gut feeling: what the medical terms really mean

Coeliac disease affects one in 100 Australians (although it's estimated only 20 per cent are ever diagnosed). It can be genetic and is a serious immune reaction to gluten, which is a protein found in wheat.

An allergy, such as a peanut allergy, can cause potentially life-threatening immune reactions, tragically illustrated with high-profile deaths from peanuts. One in 100 adult Australians suffers from an allergy.

Irritable Bowel Syndrome (IBS) is another oft-cited reason for avoiding carbohydrates and processed, sugary food. It can have similar symptoms to food intolerances - bloating, nausea and diarrhoea - but relates to a sensitive bowel.

An intolerance does not involve the immune system; it is a chemical reaction and inability to properly digest a food (lactose intolerance, for example, results from insufficient gut enzymes to break it down, causing bloating, wind and nausea).

Food intolerances:

Food Intolerance Network www.fedupwithfoodadditives.info
Self Essentials www.self.net.au (02) 9555 4810
Support for those with eating disorders:
NSW Eating Disorders Foundation www.edf.org.au (02) 9412 4499
VIC Eating Disorders Foundation www.eatingdisorders.org.au (03) 9885 0318
ACT Eating Disorders Program (02) 6205 1519
QLD Eating Disorders Association www.eda.org.au (07) 3394 3661
SA Eating Disorders Association www.edasa.org.au (08) 8297 4011
WA Women's Healthworks (08) 9300 1566
TAS Tasmanian Eating Disorders Website www.tas.eatingdisorders.org.au 1800 675 028