Coeliac disease is on the rise among children, research suggests.
The condition occurs when a person's immune system mistakenly attacks their tissues after they eat gluten – a protein in wheat, barley and rye.
At least one in 100 people in the UK is thought to have coeliac disease, however, just three in 10 (30%) have been diagnosed. Continuing to eat glutenous food – like bread, pasta and cake – can damage the small intestine, leaving it less able to absorb nutrients.
With the disease's prevalence among children being less clear, scientists from the Marche Polytechnic University in Italy screened more than 7,000 youngsters aged five to 11.
Read more: Vegan diet cuts severe COVID risk by 73%
Results reveal 1.6% of the children had coeliac disease, suggesting it has become twice as common among young people over the past 25 years.
The condition can develop at any age, but often arises between eight and 12 months old. It can take several years for a patient to be diagnosed, however, with affected children often growing slowly or going through puberty at an older age.
"Our study showed [the] prevalence of coeliac disease in schoolchildren has doubled over the past 25 years when compared to figures reported by our team in a similar school age group," said lead author Professor Elena Lionetti.
"Our sentiment is there are more cases of coeliac disease than in the past and we could not discover them without a screening strategy."
Read more: Green tea compound could combat severe COVID
Coeliac disease's exact cause is unclear. It is known to run families, with certain genetic mutations linked to a higher risk of the condition.
Enduring a gastrointestinal infection in early life, or eating gluten at just a few months old, has also been associated with the disease.
To better understand coeliac disease's prevalence among children, the Marche scientists screened thousands of children across eight Italian provinces.
The youngsters underwent a finger-prick test to look for mutations to the genes Human Leukocyte Antigens, which predispose people to the disease.
If a child tested positive for the mutations, they were checked for antibodies against gluten. Antibodies are proteins released by the immune system in response to an infection. In coeliac disease, a patient's antibodies mistakenly combat gluten.
Finally, the children were diagnosed with coeliac disease according to medically-recognised criteria.
Read more: Milk boosts heart health
Overall, 1.6% of the children had coeliac disease, as presented at the World Congress of Paediatric Gastroenterology, Hepatology and Nutrition meeting. This is twice the prevalence unveiled by a similar study by the same scientific group 25 years ago.
It is unclear why coeliac disease may be becoming more common among children.
"At the moment 70% of coeliac disease patients are going undiagnosed and this study shows significantly more could be identified, and at an earlier stage, if screening were carried out in childhood with non-invasive screening tests," said Professor Lionetti.
"Diagnosis and avoiding gluten could potentially prevent damage to the villi [finger-like projections that line the gut], which can lead to malabsorption of nutrients and long-term conditions such as growth problems, fatigue and osteoporosis."
Watch: Five gluten-free desserts
With many patients being misdiagnosed with irritable bowel syndrome (IBS) initially, the scientists are calling for the roll-out of a mass screening programme for coeliac disease.
"The study has shown screening is an effective tool for diagnosing coeliac disease in children which could potentially help avoid a lot of unnecessary suffering from what can be a hard-to-detect condition," said Professor Lionetti.
Routine testing is not in place in the UK. People may be checked for coeliac disease if they endure persistent symptoms or have a family history of the condition.
"This new study adds to the growing evidence base that the number of people in Europe with coeliac disease is rising, yet many still remain undiagnosed," said Tunde Koltai, chair of the Association of European Coeliac Societies.
"It is essential we adopt an effective screening strategy for coeliac disease across Europe to ensure children and the wider population are diagnosed as early as possible so they can have the best possible quality of life".
Coeliac disease can trigger gut-related symptoms, like diarrhoea, abdominal pain, bloating, indigestion and constipation. Some also endure fatigue, unintentional weight loss, rashes, infertility, nerve damage and poor balance, co-ordination or speech.
Over time, continuing to eat gluten can lead to weakened bones and anaemia. Less common complications include bowel cancer.
Coeliac disease is considered incurable, with a strict gluten-free diet the only treatment.