Three key substances in the gluten found in wheat, rye and barley trigger celiac disease

The precise cause of the immune reaction that leads to coeliac disease has been discovered.

Three key substances in the gluten found in wheat, rye and barley trigger the digestive condition, UK and Australian researchers say.

This gives a potential new target for developing treatments and even a vaccine, they believe.

Coeliac disease is caused by an intolerance to gluten found in foods like bread, pasta and biscuits.

It is thought to affect around 1 in every 100 people in the UK, particularly women.

The link between gluten and coeliac disease was first established 60 years ago but scientists have struggled to pinpoint the precise component in gluten that triggers it.

The research, published in the journal, Science Translational Medicine, studied 200 patients with coeliac disease attending clinics in Oxford and Melbourne.

The volunteers were asked to eat bread, rye muffins or boiled barley. Six days later they had blood samples taken to measure their immune response to thousands of different gluten fragments, or peptides.

The tests identified 90 peptides that caused some level of immune reaction, but three were found to be particularly toxic.

Professor Bob Anderson, head of the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, said: "These three components account for the majority of the immune response to gluten that is observed in people with coeliac disease."

Coeliac disease can be managed with a gluten-free diet but this is often a challenge for patients. Nearly half still have damage to their intestines five years after starting a gluten-free diet.

Professor Anderson said one potential new therapy is already being developed, using immunotherapy to expose people with coeliac disease to tiny amounts of the three toxic peptides.

Early results of the trial are expected in the next few months.

Sarah Sleet, Chief Executive of the charity Coeliac UK, said the new finding could potentially help lead to a vaccine against coeliac disease but far more research was needed.

She said: "It's an important piece of the jigsaw but a lot of further work remains so nobody should be expecting a practical solution in their surgery within the next 10 years."

The symptoms of coeliac disease vary from person to person and can range from very mild to severe.

Possible symptoms include diarrhoea, nausea and vomiting, recurrent stomach pain, tiredness, headaches, weight loss and mouth ulcers.

Some symptoms may be mistaken as irritable bowel syndrome or wheat intolerance.