Coeliac disease is a chronic autoimmune disorder in which eating gluten causes the immune system to damage the lining of the small intestine. Gluten is a group of proteins found in wheat, barley and rye and is therefore present in many common foods, including bread, pasta, cakes, biscuits and numerous processed products. In susceptible individuals, components of gluten, particularly peptides derived from gliadin, initiate an abnormal immune response.
This response produces inflammation and damages the intestinal mucosa, including the villi that normally provide a large absorptive surface. The resulting impairment of nutrient absorption is called malabsorption. Coeliac disease is therefore not simply an intolerance in the everyday digestive sense and is not the same as a wheat allergy. It is a systemic autoimmune condition triggered by dietary gluten in genetically susceptible people.
The small intestine is central to understanding the disease because its lining is specialised for nutrient absorption. Millions of microscopic projections called villi increase the available surface area through which nutrients can pass into the body. In untreated coeliac disease, immune-mediated inflammation damages and flattens these structures, reducing the intestine's absorptive capacity. This can interfere with the uptake of iron, folate, vitamin B12, calcium and other nutrients, although the precise pattern varies between individuals.
Malabsorption helps explain why coeliac disease can produce symptoms beyond the digestive system, including fatigue, anaemia, weight loss, neurological problems and impaired growth in children. The intestinal damage can occur even when gastrointestinal symptoms are mild or absent, which is one reason diagnosis and treatment are important even for people who do not feel obviously ill after eating gluten.
Coeliac disease can present at any age and has a broad spectrum of clinical expression. Some people develop prominent diarrhoea, abdominal pain and bloating, while others have predominantly non-gastrointestinal manifestations such as iron-deficiency anaemia, unexplained fatigue, osteoporosis or neurological symptoms. Some people have few or no noticeable symptoms and are identified because they belong to a higher-risk group or are investigated for another condition.
NHS information estimates that coeliac disease affects at least one in 100 people in the UK, while recognising that some cases remain undiagnosed. First-degree relatives of affected people have increased risk, as do people with certain other autoimmune or genetic conditions, including type 1 diabetes, autoimmune thyroid disease, Down's syndrome and Turner syndrome.
Diagnosis generally begins with blood testing for antibodies associated with coeliac disease while the person continues to eat gluten. The reason for continuing gluten is fundamental: reducing or eliminating gluten can reduce the immune response and cause blood tests or intestinal examination to become falsely reassuring. People with positive antibody tests are generally referred for specialist assessment, and an intestinal biopsy may be required to confirm the diagnosis depending on age, clinical circumstances and current diagnostic pathways.
NHS guidance also notes that a person can occasionally have coeliac disease despite negative blood antibodies, so persistent compatible symptoms can warrant further specialist evaluation. Testing is particularly relevant for people with persistent unexplained gastrointestinal symptoms, prolonged fatigue, unexplained weight loss, certain anaemias, type 1 diabetes, autoimmune thyroid disease, irritable bowel syndrome in adults, or a first-degree relative with coeliac disease.
The treatment for confirmed coeliac disease is a strict gluten-free diet maintained for life. Removing gluten prevents the continuing immune stimulus and allows the intestinal lining to recover. Symptoms commonly improve considerably within weeks, although complete healing of the digestive tract can take considerably longer and may take years in some people. Dietary management requires attention to ingredients, food preparation, cross-contamination and nutritionally balanced substitutes.
A dietitian can help people understand naturally gluten-free foods, certified gluten-free products, nutritional requirements and practical strategies for eating outside the home. Unlike a temporary elimination diet used diagnostically for some intolerances, gluten avoidance in coeliac disease is a permanent medical treatment because re-exposure can reactivate intestinal damage even when symptoms are not immediately apparent.
Untreated or inadequately treated coeliac disease can have consequences beyond gastrointestinal discomfort. Malabsorption can lead to iron deficiency and iron-deficiency anaemia, folate or vitamin B12 deficiency, low bone mineral density and osteoporosis. Neurological complications can include peripheral neuropathy and ataxia. Fertility and pregnancy can also be affected in some individuals, while children may experience impaired growth or delayed puberty. More serious complications are uncommon but can include certain intestinal malignancies and other severe consequences of prolonged intestinal disease. The risk profile is influenced by whether the disease remains untreated or whether gluten exposure continues. Effective adherence to a gluten-free diet substantially changes the clinical course by allowing intestinal healing and reducing the consequences associated with ongoing gluten-driven inflammation.
Coeliac disease is closely related to genetics but is not caused by genetics alone. Particular HLA gene variants, especially HLA-DQ2 and HLA-DQ8-related genetic backgrounds, are strongly associated with susceptibility. However, these variants are relatively common in the general population, whereas only a minority of genetically susceptible people develop coeliac disease. This means that genetic susceptibility is necessary for most cases but is not sufficient by itself.
Environmental and biological factors also appear to influence whether disease develops, including gastrointestinal infections and other factors affecting immune regulation. Family history therefore raises risk but does not guarantee disease, while the absence of a known family history does not exclude it. The condition illustrates how genetic predisposition and environmental exposure can combine to produce an autoimmune disorder.
Coeliac disease should be distinguished from non-coeliac gluten sensitivity and wheat allergy because the three conditions involve different mechanisms and clinical implications. Coeliac disease produces characteristic autoimmune intestinal injury and requires lifelong strict gluten avoidance. Non-coeliac gluten sensitivity does not have the same established autoimmune intestinal pathology, while wheat allergy is an allergic immune reaction to wheat proteins and can produce rapid allergic symptoms.
Coeliac disease is also different from lactose intolerance, although untreated coeliac disease can temporarily cause secondary lactose intolerance because damage to the small-intestinal surface can reduce lactase activity. Understanding these distinctions prevents inappropriate self-diagnosis and explains why someone experiencing symptoms after eating bread should undergo appropriate assessment rather than assuming that all gluten-related conditions are interchangeable.
