What is Coeliac Disease?
Coeliac disease is a chronic autoimmune condition that affects the digestive system, particularly the small intestine. When someone with coeliac disease eats foods containing gluten—a protein naturally present in wheat, barley, and rye—their immune system mistakenly treats it as a threat and launches an attack. This abnormal immune response causes inflammation and damage to the lining of the small intestine, which is responsible for absorbing nutrients from the food we eat.[1][2]
The small intestine is lined with tiny, finger-like projections called villi, which help break down and absorb nutrients. When someone with coeliac disease eats gluten, these villi become inflamed and damaged in a process called villous atrophy. This flattening of the villi reduces the surface area available for nutrient absorption, making it difficult for the body to get the vitamins, minerals, and other essential nutrients it needs from food. Over time, this can lead to malabsorption and malnutrition, even if a person is eating a healthy diet.[2][15]
It’s important to understand that coeliac disease is not the same as a food allergy or gluten sensitivity. While gluten sensitivity can cause similar symptoms like abdominal pain and tiredness, it does not cause the same intestinal damage seen in coeliac disease. A wheat allergy, on the other hand, is an immune reaction to wheat that can cause different symptoms such as itchy eyes or difficulty breathing, but it also doesn’t lead to long-term intestinal harm. Coeliac disease is unique in that even small amounts of gluten can trigger damage, and this damage can continue even if symptoms are mild or absent.[3][6]
Epidemiology: Who Gets Coeliac Disease?
Coeliac disease is more common than many people realize. Experts estimate that about 1 in 100 people in the United Kingdom have the condition, though many cases remain undiagnosed or misdiagnosed as other digestive problems like irritable bowel syndrome. In the United States, approximately 2 million people have coeliac disease, representing about 1 percent of the population worldwide.[3][5]
The condition affects people across all age groups and can develop at any stage of life, though healthcare providers notice it often appears during two distinct time periods. The first window is in early childhood, typically between 8 and 12 months of age, when babies begin eating solid foods containing gluten such as crackers or cereals. The second common time for diagnosis is during middle age, between the ages of 40 and 60.[4][13]
Demographically, coeliac disease shows some interesting patterns. In the United States, it is more common among white Americans compared to other racial or ethnic groups. The condition also appears to affect more females than males—women are more likely to receive a diagnosis than men. However, this could partly reflect differences in healthcare-seeking behavior rather than true biological differences.[3]
One of the biggest challenges with coeliac disease is that many people who have it don’t know they have it. Some estimates suggest that as many as 97% of people with the condition remain undiagnosed. This happens because symptoms can be very mild, atypical, or even completely absent, making it easy to overlook the disease or attribute symptoms to other common conditions.[15]
Causes of Coeliac Disease
Coeliac disease develops when someone with a genetic predisposition is exposed to gluten. The exact cause isn’t entirely clear, but research has shown that it involves a combination of genetic factors and environmental triggers. Almost everyone with coeliac disease has specific gene variations known as HLA-DQ2 or HLA-DQ8. These genes are inherited from biological parents and affect how the immune system recognizes and responds to gluten proteins.[4][13]
However, having these genes doesn’t guarantee that someone will develop coeliac disease. Many people carry these genetic variants but never develop the condition, which tells us that other factors must be involved in triggering the disease. Researchers believe that the balance of microorganisms living in the gut might play a role, as might major physical events such as illness, surgery, pregnancy, or severe stress. These events could potentially trigger the onset of coeliac disease in someone who is genetically susceptible, though more research is needed to fully understand these mechanisms.[4][13]
The disease is triggered specifically by gluten, which is found in wheat, barley, and rye. Within gluten, different protein fractions cause problems for people with coeliac disease: gliadin in wheat, secalin in rye, hordein in barley, and avenin in oats. When someone with coeliac disease eats these proteins, their immune system responds abnormally, attacking not just the gluten but also the person’s own intestinal tissue.[15]
Risk Factors for Developing Coeliac Disease
Several factors can increase a person’s likelihood of developing coeliac disease. The most significant risk factor is having a family member with the condition. Because coeliac disease has a strong genetic component, first-degree relatives—parents, siblings, and children—of people with coeliac disease have a higher risk of developing it themselves. These family members should be tested even if they don’t have symptoms.[5]
Certain genetic syndromes also increase risk. People with Down syndrome, Turner syndrome, or Williams syndrome are more likely to develop coeliac disease compared to the general population. Additionally, having other autoimmune conditions raises the risk. People with type 1 diabetes or autoimmune thyroid disease have an increased likelihood of also having coeliac disease, as autoimmune conditions often occur together.[3][5]
The presence of the HLA-DQ2 or HLA-DQ8 genes is necessary for coeliac disease to develop—you cannot have coeliac disease without carrying at least one of these gene variants. However, these genes are relatively common in the population, and most people who have them never develop the disease. This means that while genetic testing can rule out coeliac disease (if you don’t have the genes, you won’t develop it), having the genes alone doesn’t mean you will definitely get it.[4]
Symptoms of Coeliac Disease
The symptoms of coeliac disease vary tremendously from person to person, which makes diagnosis challenging. Some people experience severe digestive problems, while others have no noticeable symptoms at all. The range and intensity of symptoms can also change over time, with periods where symptoms come and go.[2][6]
Digestive symptoms are more common in children than adults, though people of any age can experience them. These gastrointestinal signs include chronic diarrhea that may have a particularly unpleasant smell, stomach aches, bloating and excessive gas, nausea and vomiting, and sometimes constipation instead of diarrhea. Some people notice that their stools appear greasy or bulky. Because the damaged intestine can’t properly absorb lactose from dairy products, many people with untreated coeliac disease also develop temporary lactose intolerance, which adds to their digestive discomfort.[2][5][6]
More than half of adults with coeliac disease have symptoms that affect parts of the body beyond the digestive system. These extraintestinal symptoms can be the first or only signs of the disease, which often delays diagnosis because they don’t seem related to food or digestion. Common non-digestive symptoms include extreme fatigue and weakness, unexplained weight loss (or failure to gain weight appropriately in children), and signs of anemia such as paleness, feeling cold, and indented or concave fingernails. Many people experience iron-deficiency anemia even when they’re not bleeding anywhere, because the damaged intestine cannot absorb iron properly.[2][4][6]
Bone and joint pain can occur due to poor absorption of calcium and vitamin D, potentially leading to weakened bones. Women may experience irregular menstrual periods or have difficulty getting pregnant. Children with undiagnosed coeliac disease may not grow at the expected rate and might have delayed puberty. Dental problems such as enamel defects can develop, and some people experience neurological symptoms including headaches, balance problems, or peripheral neuropathy (numbness or tingling in the hands and feet). Mood changes are also common, with many people reporting irritability, depression, or anxiety.[2][4][6]
Around 15% of people with coeliac disease develop a distinctive skin condition called dermatitis herpetiformis. This itchy rash appears as clusters of bumps or blisters, typically on the elbows, knees, buttocks, and scalp. Despite its name, it has nothing to do with the herpes virus—it’s actually another way that coeliac disease manifests in the body.[4][6]
Prevention of Coeliac Disease
Currently, there is no known way to prevent coeliac disease from developing in people who carry the genetic risk factors. The condition cannot be prevented through lifestyle changes, dietary modifications before onset, or vaccinations. Once someone has the genetic predisposition, exposure to gluten at some point in life may trigger the disease, though the timing and circumstances vary greatly between individuals.[2]
Past research explored whether the timing of introducing gluten to babies might affect their risk of developing coeliac disease, but current evidence doesn’t support delaying gluten introduction beyond the normal age for starting solid foods. Healthcare guidelines now recommend not introducing gluten into a baby’s diet before 6 months of age, but there’s no proven benefit to delaying it further. Both breast milk and all infant formulas are naturally gluten-free.[9][19]
For people already diagnosed with coeliac disease, preventing complications is possible through strict adherence to a gluten-free diet for life. This prevents further intestinal damage and allows the intestine to heal. Following the diet consistently also reduces the risk of long-term complications such as osteoporosis, certain cancers, and other serious health problems. Regular follow-up with healthcare providers, including annual reviews to monitor growth, weight, symptoms, and nutritional status, helps ensure the disease is well-managed.[9][19]
Screening family members of people with coeliac disease is an important preventive measure, even when they don’t have symptoms. Early detection through screening allows for earlier treatment, which can prevent the development of complications and improve long-term health outcomes. First-degree relatives should be tested for coeliac disease regardless of whether they have symptoms.[5]
Pathophysiology: How Coeliac Disease Affects the Body
Understanding how coeliac disease works in the body helps explain why it causes such wide-ranging symptoms. When someone with coeliac disease eats gluten, the immune system identifies it as harmful and triggers an inflammatory response in the small intestine. This inflammation specifically targets and damages the villi—those tiny, finger-like projections that line the intestinal wall.[2][4]
In a healthy person, villi create a large surface area for absorbing nutrients from food, much like how the fibers of a towel increase its ability to soak up water. When villi are damaged and become flattened through villous atrophy, this surface area shrinks dramatically. The small intestine loses much of its ability to break down food and extract nutrients. This leads to malabsorption, where essential nutrients pass through the digestive system without being absorbed into the bloodstream.[2][15]
The malabsorption affects different types of nutrients in various ways. Fat-soluble vitamins (A, D, E, and K) cannot be absorbed properly, leading to deficiencies that affect vision, bone health, blood clotting, and cellular function. Iron and folate absorption is impaired, causing anemia. Calcium and vitamin D deficiency leads to bone problems and potential osteoporosis. Protein and calorie malabsorption result in weight loss and, in children, growth faltering and delayed development.[2][4][6]
The immune system’s response to gluten also involves the production of specific antibodies. The enzyme tissue transglutaminase plays a key role in this process. When gluten enters the intestine, tissue transglutaminase modifies gluten proteins, making them more recognizable to the immune system. The immune system then produces antibodies against both the modified gluten and tissue transglutaminase itself. These antibodies can be detected in blood tests and are used to help diagnose coeliac disease.[8]
Beyond the intestine, inflammation can affect other parts of the body, explaining the extraintestinal symptoms. The immune system’s overactivity and the resulting nutritional deficiencies can impact the nervous system, bones, skin, reproductive organs, and other tissues. In some people, the spleen doesn’t work as effectively, which can increase susceptibility to certain infections. This is why some people with coeliac disease may need additional vaccinations.[9][19]
The good news is that this damage is often reversible. When gluten is completely removed from the diet, inflammation subsides and the villi can begin to regenerate and heal. Many people see improvement in their symptoms within days to weeks of starting a gluten-free diet. Complete healing of the intestinal lining can take longer—sometimes several months to a few years—but for most people, the intestine can recover fully if the gluten-free diet is maintained strictly.[9][10][19]
Complications of Untreated Coeliac Disease
When coeliac disease goes undiagnosed or untreated, or when someone with the condition continues to consume gluten, serious health complications can develop over time. The ongoing intestinal damage and chronic malabsorption take a toll on multiple body systems.[4][5]
Malnutrition is one of the most immediate concerns. When the body cannot absorb nutrients properly, deficiencies develop even if a person is eating a seemingly healthy diet. Iron-deficiency anemia is particularly common and causes fatigue, weakness, and poor concentration. Vitamin B12 and folate deficiencies can also lead to anemia and neurological problems. Inadequate absorption of calcium and vitamin D weakens bones, leading to osteoporosis (brittle, fragile bones) and an increased risk of fractures. This bone disease can develop even in young adults with untreated coeliac disease.[2][5][6]
In children, the consequences of untreated coeliac disease are particularly concerning. Chronic malnutrition during crucial developmental years can result in stunted growth and delayed puberty. Children may not reach their expected adult height. Cognitive development may also be affected, potentially impacting learning and school performance. Addressing the disease early in childhood allows children to catch up on growth and development.[2][4]
Reproductive health can be affected in both men and women. Women with untreated coeliac disease may experience irregular or absent menstrual periods and have difficulty becoming pregnant. Miscarriages may occur more frequently. In men, fertility can also be reduced, though this is less well studied.[2][6]
There is a small but real increased risk of certain types of cancer in people with untreated coeliac disease. The most concerning is intestinal lymphoma, a cancer of immune cells in the small intestine. The risk of bowel cancer may also be slightly elevated. However, following a strict gluten-free diet significantly reduces these cancer risks, bringing them much closer to that of the general population.[5][9][19]
Long-term inflammation and nutritional deficiencies can lead to nervous system problems including peripheral neuropathy, balance and coordination difficulties, and in rare cases, a condition called ataxia that affects movement. Depression and anxiety are more common in people with untreated coeliac disease, possibly due to both the physical effects of malnutrition and the chronic nature of feeling unwell.[2][6]
The encouraging news is that following a strict gluten-free diet can prevent virtually all of these complications. Early diagnosis and treatment offer the best outcomes, allowing the intestine to heal before serious damage occurs. Even when complications have already developed, many improve or stabilize once a gluten-free diet is implemented and nutritional deficiencies are corrected.[9][10]
