Scientists have found a new genetic risk factor for coeliac disease, an immune disorder that stops people eating wheat-based food. More than 125,000 people in the UK are diagnosed with the disease but there could be a further 500,000 people who do not know they have it.

The condition is caused by an intolerance to gluten, a protein in wheat, barley and rye, which causes damage to the gut and prevents normal digestion. It runs in families and, if left undetected, can lead to anaemia, poor bone health and weight loss.

David van Heel, of Queen Mary University of London, who led the study, said: "The first findings suggest that interleukin genes that control inflammation are critical. We expect to find more disease risk factors from in-depth analysis."

The team compared the gene sequences of coeliac disease sufferers to those of 1,500 healthy people. The latter were more likely to have a protective section of DNA in the interleukin-2 and interleukin-21 regions, sections responsible for the production of proteins, called cytokines, used to control inflammation. The amount of cytokines in people without coeliac disease could be protecting them against inflammation in the gut, they said. The results are published today in Nature Genetics.

Sarah Sleet, chief executive of Coeliac UK, said: "This research heralds an important breakthrough in understanding better who is likely to develop coeliac disease." Current genetic testing was a blunt instrument, able to narow the search only to around a third of the general population, she said.

Using similar methods, scientists last week announced more than 20 genetic links for common illnesses such as diabetes, heart disease and Crohn's disease.