‘‘I really have to look at every single thing I put in my mouth,’’ says the 44-year-old French teacher. Love has a food intolerance that is as complicated as it is common.

Usually described as ‘‘fructose intolerance’’, but often extending to malabsorption of other sugars, scientists believe the condition could affect almost half of the 15 per cent of Australians with irritable bowel syndrome (IBS), and be the prime trigger of symptoms such as diarrhoea, constipation, bloating and pain.

Diagnosis is confirmed by a breath-test, and the number of specialist diagnostic centres in Melbourne has risen since 1999 from one to an estimated 18.

Sufferers are treated with a low FODMAP diet, which stands for six sugars.  It restricts most fruits, many vegetables, wheat, some dairy and other everyday foods such as honey.

‘‘Some people just give up on asking you out for dinner — it’s that difficult to work out,’’ says Ms Love. But she says her painful and socially awkward IBS symptoms have disappeared, and as a FODMAP-follower she’s not alone.

The diet, which was developed in Melbourne by dietitian Dr Sue Shepherd in 1999 and later proved effective by Dr Shepherd and Monash University, has spawned a thriving local industry.

‘‘There are lots of diets being promoted ... but this is one where we know why it works,’’ says Dr Shepherd.

Her annual patient list has soared from 100 to 4000 in 13 years (about 80per cent of whom are being treated with the FODMAP diet) and she also publishes cookbooks, consults overseas and conducts supermarket tours and information sessions for chefs.

Natalie Nott, 35, is among her acolytes. ‘‘FODMAPs has really changed everything.’’ Relieved of her irritable bowel syndrome symptoms, last year she self-published the Low Fodmap Cookbook, which has sold about 600 copies, and has 1000 subscribers to her blog.

She says dining out is still difficult, but restaurants such as Fox in the Box, in Hampton, and The Firehouse, in Ringwood, now cater specifically for FODMAPs.

Food companies Naturally Good and Simply Wise include a ‘‘fructose-friendly’’ label on relevant products.
Meanwhile, breath-testing clinics are booked out weeks in advance. Paul Rose, manager at Stream Diagnostics, says the company’s Box Hill and Brighton centres conduct about 300 breath-tests a week, and that about 60 per cent of clients test positive for fructose malabsorption.

Patients drink a solution of fructose and then breathe into a device similar to a police breathalyser several times over three hours. Malabsorption is indicated by increased hydrogen in the breath. The tests costs between $85 and $100 each and there is no Medicare or private health insurance rebate.

Karen McHarg, 42, an administrator, asked for a referral from a GP after hearing about fructose malabsorption at work. ‘‘Of a workplace of about 200 people, I know of 10 who have been diagnosed or who are following the FODMAP diet.’’

She hopes they will provide an answer to her IBS issues. Dr Shepherd says better diagnosis of fructose malabsorption has made the condition seem more prevalent, although some speculate that increased fructose in our diets, particularly from high-fructose corn syrup in many processed foods, is also to blame.

But Australian Medical Association president Steve Hambleton said  the incorrect perception of food allergies and intolerances was also on the rise, and warned that the FODMAP diet should only be used under professional guidance.

‘‘You need to go to a GP first to make sure you don’t have a serious, treatable medical condition — especially one of the inflammatory bowel diseases,’’ he said.

‘‘There is an objective increase in recognised food intolerances, But there’s probably an equal number of people who think they’re intolerant or allergic without robust reason.’’

nbc@theage.com.au