What is coeliac disease?
Coeliac disease is a chronic autoimmune condition where the immune system reacts abnormally to gluten – a protein found in wheat, barley and rye.
In people who are genetically prone, eating gluten can inflame the small intestine and, over time, flatten the lining so your body can’t absorb nutrients properly.
It affects about 1 in 100 people worldwide, is more common in women, and can cause digestive symptoms, as well as nutrient deficiencies.
What is gluten?
Gluten is a group of proteins found in the seeds of several common grains like wheat, rye and barley, and also some varieties of oats
It’s also present in related grains or hybrids, such as spelt, escanda or kamut. These proteins help give dough its elasticity – so they’re what make bread soft and chewy.
For most people gluten is harmless, but in people with coeliac disease, even small amounts can trigger the immune system. When they eat gluten, their body reacts as if it’s a threat.
The tricky part is that gluten isn’t just in obvious foods like bread or pasta. It’s widely used in processed foods because it works as a thickener, stabiliser or filler. This means it can show up in things like sauces, soups, dressings, processed meats and packaged snacks – even when you wouldn’t expect it! That’s why the gluten-free diet needs to be quite strict and broad: avoiding gluten isn’t just about cutting out certain grains, but also carefully checking labels to make sure it’s not hidden in everyday products.
Most countries have guides or websites where you can check if a product is certified gluten-free.
In Australia, you can use the Coeliac Australia endorsed product list at https://coeliac.org.au/
It’s best to check local sources, as a product may have different ingredients in different countries.
What causes coeliac disease?
Coeliac disease starts with a genetic predisposition, which means your body is more likely to mistake gluten as something harmful. But having the genes doesn’t automatically mean you’ll develop it. At some point, the body loses its tolerance to gluten and starts reacting to it, causing inflammation in the small intestine.
Even if you’ve eaten gluten your whole life, coeliac disease can still develop later on. Things like gut infections, antibiotics or changes in your gut bacteria may play a role, although the exact cause isn’t fully understood yet.
A combination of your genes and environmental factors causes the immune system to react in the wrong way.
What are the symptoms?
If you have coeliac disease, your body reacts to gluten in a way it shouldn’t. Instead of simply digesting it, your immune system treats it as a threat and inflammation in the lining of the small intestine starts. Over time, this damages the part of the bowel that absorbs nutrients, especially iron, calcium and some vitamins – even if you are eating well.
This inflammation in the small bowel can cause symptoms like bloating, diarrhoea, constipation, stomach pain and excess gas, along with nutrient deficiencies.
Because the immune reaction involves the whole body, symptoms can appear in many different ways. You might feel constantly tired, experience ‘brain fog’ or lose weight from poor nutrient absorption.
Ongoing inflammation and low nutrient levels can also affect the body more broadly. You might notice muscle cramps, headaches or changes in your menstrual cycle – like irregular periods – and in some cases, problems to get pregnant.
You might also notice itchy, blistery skin rashes, caused by your immune system reacting to gluten and mistakenly targeting the skin.
Coeliac disease is more than a gut problem and can show up in lots of different ways throughout the body.
Coeliac disease and nutrient absorption
Everything starts in your gut. When gluten reaches the small intestine, it activates immune cells in the gut lining. These cells release signals that inflame the tiny, finger-like structures called villi, which normally help absorb nutrients from your food.
The first part of your small bowel, called the duodenum, is the hotspot. It’s where the immune system first reacts and detects gluten. Because the duodenum is where iron, folate, calcium and zinc are mainly absorbed, damage here quickly leads to deficiencies. If the immune reaction continues, it can spread to other parts of the small intestine, affecting absorption of even more nutrients.
Over time, the lining of the intestine becomes inflamed and flattened, making it less effective at absorbing nutrients. The gut can also become more ‘leaky’, allowing nutrients to pass through before the body has a chance to properly absorb them.
The combination of damaged villi and leaky gut explains why people with coeliac disease often develop nutrient deficiencies, even if they are eating well.
How do you know it’s coeliac disease?
If your doctor thinks your symptoms might be due to coeliac disease, the first step is usually a set of blood tests.
These check whether your immune system is reacting abnormally to gluten.
- tTG-IgA (tissue transglutaminase antibodies)
Main screening test. High levels suggest coeliac disease. - Total IgA
Checks whether your body makes enough IgA antibodies. This is important because the tTG-IgA test relies on IgA to work properly. Around 2–3% of people with coeliac disease have low IgA levels, meaning results may appear low or negative – even if coeliac disease is present. - IgG-based tests (if needed)
Used if IgA levels are low, to detect a similar immune response using a different antibody type. - EMA-IgA (anti-endomysial antibodies)
A highly specific test, usually used if the diagnosis is unclear.
If the blood tests suggest coeliac disease, your doctor will usually recommend an endoscopy. This involves passing a thin tube into the small intestine to take tiny samples. These samples are examined for damage to the intestinal lining, which confirms the diagnosis.
Sometimes, the process happens in reverse – a biopsy shows these changes first and blood tests are used to confirm the cause.
It is very important that you are eating gluten before and during testing. If you have already removed gluten from your diet, the results may appear normal even if you do have coeliac disease.
Researchers are currently exploring less invasive tests, such as saliva or stool testing, but these are not yet available for diagnosis.
Diagnosis usually involves blood tests followed by a biopsy to confirm the condition.
Genetic testing
In certain situations, a genetic test may be used to look for specific genes associated with coeliac disease: HLA-DQ2 or HLA-DQ8. If these genes are not present, coeliac disease is extremely unlikely. However, many people without the condition also carry these genes, so the test on its own cannot confirm the diagnosis.
It is mainly used when blood test results are unclear or if someone has already started a gluten-free diet.
Screening
Doctors may recommend testing people at higher risk, even if they have no symptoms. This includes close family members of someone with coeliac disease and people with certain related conditions, such as type 1 diabetes, autoimmune thyroid disease or Down syndrome.
What is the treatment?
The treatment for coeliac disease is a strict gluten-free diet. This means completely avoiding foods that contain gluten for life.
Following the diet carefully is essential. It helps relieve symptoms, prevents nutritional deficiencies and allows the small intestine to heal.
Symptoms usually start to improve within 2-4 weeks of starting a gluten-free diet, but the gut doesn’t heal overnight. Even when symptoms ease and blood tests return to normal, full recovery of the intestinal lining is slower – often taking around 3 years and sometimes even longer for some people.
Many drugs are being studied to target the disease in different ways, but for now, diet is the only proven way to manage coeliac disease.
Gluten free diet: the hidden challenges
Going gluten-free is essential for managing coeliac disease – but it’s not automatically a healthy diet.
At diagnosis, your gut may struggle to absorb nutrients, so deficiencies in iron, calcium, vitamin D, vitamin B12, zinc and folate are common. These usually improve as your intestine heals on a gluten-free diet.
However, over time, nutrition gaps can still appear, not because of absorption, but due to daily food choices. Many people focus on avoiding gluten and overlook overall balance.
Shop-bought gluten-free products are often low in fibre and sometimes high in sugar and fat, which can lead to nutrient gaps affecting energy and bone health. That’s why it’s important to monitor your nutrition regularly.
Packaged products can be convenient but shouldn’t make up most of your diet. Always check labels and choose certified gluten-free items, as gluten can hide in sauces or processed foods as a thickener or stabiliser.
Avoid cross-contamination – even small traces of gluten from utensils, cooking surfaces, or non-certified oats can cause problems.
A healthy gluten-free diet emphasises naturally gluten-free foods like fruits, vegetables, legumes, dairy, eggs, meat, fish, nuts and seeds, along with nutrient-rich grains such as quinoa, buckwheat and amaranth.
A gluten-free diet heals your gut.
To feel your best, focus on building a diet that’s balanced, varied and nourishing, not just gluten-free.
Monitoring and follow-up
After diagnosis, regular follow-up is important. Blood tests are used to monitor how well the diet is working.
- An initial review is usually done 3–6 months after diagnosis, checking symptoms, blood tests and nutritional status.
- Ongoing reviews are typically every 12 months for adults, until blood tests return to normal.
If blood tests remain abnormal, this may suggest ongoing gluten exposure (often accidental).
A newer way to check recent gluten intake is by testing for gluten immunogenic peptides (GIP). These are tiny fragments of gluten that pass through the body and can be detected in urine or stool. A positive result means gluten has been eaten recently.
GIP test can be very helpful for spotting accidental gluten intake or understanding whether ongoing symptoms are due to diet slip-ups or other causes.
Why treatment matters?
If coeliac disease isn’t diagnosed or managed, it can cause nutrient deficiencies, leading to anaemia, low bone density or even slowed growth in children. Adults may also experience fatigue, digestive issues or unintended weight loss.
People with untreated or persistent intestinal damage also have a slightly higher risk of certain type of lymphomas.
Gluten-Free for everyone?
Not at all. Unless you have coeliac disease or a diagnosed gluten sensitivity, cutting out gluten won’t make you healthier. In fact, if you rely mostly on processed gluten-free foods, you could miss out on important nutrients, get less fibre and end up eating more sugar or fat than you realise.
Gluten-free products can also be more expensive and avoiding gluten unnecessarily can make meal planning tricky.
A gluten-free diet is safest and most effective when it’s medically needed and guided by a healthcare professional. It’s all about eating well, not just cutting out gluten.
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