A diet low in poorly absorbed sugars, including fructose and lactose, can reduce symptoms of irritable bowel syndrome, a study has found.
Melbourne researchers compared the effects of a diet low in FODMAPs - it stands for six sugars - with a normal Western diet in a study of patients with irritable bowel syndrome.
Participants were provided with all of their meals throughout the study and received three weeks each of a low-FODMAP and normal Western diet, without knowing which diet they were receiving.
The study, published in the journal Gastroenterology, found a diet low in the poorly absorbed sugars significantly reduced symptoms of irritable bowel syndrome including diarrhoea, constipation, bloating and pain.
Peter Gibson, study co-author and director of gastroenterology at The Alfred hospital, said the study provided the first high-quality evidence to support the use of diet to manage irritable bowel syndrome, which affects about 15 per cent of Australians.
He said some drugs were available to treat symptoms but the evidence for reducing or excluding certain foods from the diet had previously been uncertain.
Study co-author and dietitian Emma Halmos said foods high in poorly absorbed sugars included apples, pears, onions, garlic, wheat and rye. But she said a diet low in poorly absorbed sugars did not show any benefits in a group of healthy people included in the study, who should not restrict their diet unnecessarily.
Dr Halmos said people with symptoms of irritable bowel syndrome should see their doctor and first have a test to rule out coeliac disease, in which the immune system reacts abnormally to the protein gluten found in wheat, rye, barley and oats.
Professor Gibson said many people with irritable bowel syndrome reported feeling better on a gluten-free diet but this was probably because gluten tended to co-exist with poorly absorbed sugars such as fructans in wheat.
Sandy Hirschfield took part in the study after suffering various symptoms including bloating, stomach cramps, nausea and weight gain after a bout of severe food poisoning 15 years ago.
She said she had ''very strong reactions'' to the two diets and has since adopted a diet low in poorly absorbed sugars.
''I've learnt a lot from it, what sorts of foods are high and low in FODMAPs and that my symptoms are related severely to lactose malabsorption. Every time I had any dairy product I'd be nauseous but I didn't realise that's what was causing it,'' she said. ''I've lost the bloatedness and lost weight and I feel so healthy and well without having to take drugs.''