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Celiac disease
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In one pass Celiac disease is not being sensitive to bread.
Educational content, not medical advice. See a clinician about your own case.
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Chapter 1
The enzyme turns gliadin into antigen
Celiac disease is not being sensitive to bread. It is autoimmunity: what the immune system ends up attacking is the lining of your own small intestine.
The starting point is a protein in wheat gluten called gliadin. When it reaches the small intestine, it should not be treated as an enemy. But the intestinal tissue has an enzyme, tissue transglutaminase (tTG), that happens to favor gliadin as a raw material. It changes one small chemical group on gliadin (a step called deamidation) and so creates new shapes the immune system has never seen. In people with celiac disease, antibodies then target both the modified gliadin and the enzyme itself.
For you this means two things. Treatment is not eating a bit less bread; it is strict, long-term avoidance of gluten. And the diagnosis comes from tests, not from how you feel.
The starting point is a protein in wheat gluten called gliadin. When it reaches the small intestine, it should not be treated as an enemy. But the intestinal tissue has an enzyme, tissue transglutaminase (tTG), that happens to favor gliadin as a raw material. It changes one small chemical group on gliadin (a step called deamidation) and so creates new shapes the immune system has never seen. In people with celiac disease, antibodies then target both the modified gliadin and the enzyme itself.
For you this means two things. Treatment is not eating a bit less bread; it is strict, long-term avoidance of gluten. And the diagnosis comes from tests, not from how you feel.
Mechanism · How an enzyme turns gliadin into antigen
People with celiac disease carry an antibody in their blood that sticks to the thin layer of connective tissue around muscle fibers (the endomysium), which is why it is called the anti-endomysial antibody. For a long time nobody knew which molecule it actually recognized. Dieterich 1997 found the answer: the autoantigen is tissue transglutaminase (tTG), one of the body's own tissue-repair enzymes.The same study found that gliadin is a preferred substrate of this enzyme, and that the enzyme's action gives rise to new antigenic epitopes — the small pieces of structure the immune system can recognize and treat as foreign. How they are made was filled in the next year by Molberg 1998: the enzyme selectively changes the shape of part of gliadin (deamidation), and the modified piece fits firmly into the patient's HLA-DQ2 molecule, where T cells in the gut recognize it.
Put the two findings together and the odd feature of celiac disease makes sense: antibodies go after the modified gliadin and after the enzyme. The first comes from food, the second is your own. That is why it counts as an autoimmune disease, not a food allergy or intolerance. A blood test can screen for celiac disease because it looks for exactly these antibodies against the enzyme.
How the small intestine absorbs nutrients is covered in Digestive System. This page is about why that absorptive surface gets taken apart by your own immune system.
Chapter 2
Villi are flattened
The lining of the small intestine is packed with tiny finger-like projections called villi, which make the absorptive area very large. In celiac disease the immune attack makes the villi disappear and flatten, while the small pits between them that make new cells (the crypts) grow deeper instead. The absorptive surface shrinks, and the typical result is malabsorption (Lebwohl 2018).
So iron deficiency, low vitamin D (calciferol), and weight loss are often several consequences of the same damaged surface, not three different diseases.
Diagnosis needs a blood test (serology) plus a small-intestine biopsy. Treatment is a strict gluten-free diet. Left untreated for a long time, it also carries a rare but serious risk: enteropathy-associated T-cell lymphoma.
So iron deficiency, low vitamin D (calciferol), and weight loss are often several consequences of the same damaged surface, not three different diseases.
Diagnosis needs a blood test (serology) plus a small-intestine biopsy. Treatment is a strict gluten-free diet. Left untreated for a long time, it also carries a rare but serious risk: enteropathy-associated T-cell lymphoma.
Mechanism · What follows when the lining flattens
Arrange what the Lebwohl 2018 review describes in order, and it becomes a chain you can draw one link at a time:The enzyme modifies gliadin: tissue transglutaminase reshapes gliadin, and the immune system starts treating it as an enemy.The immune attack lands on the villi: the lining of the small intestine is hit, the villi disappear, and the crypts grow.The absorptive surface flattens: the same length of small intestine has far less area left for absorbing.Malabsorption follows: nutrients that rely on the small intestine, such as iron and vitamin D, do not get in, energy falls short, and weight drops.
This chain explains a common puzzle: why some people are worked up for anemia, for their bones, or for weight loss, and only at the end of that round does celiac disease turn up. Those findings are not separate diseases. They sit downstream of the same damaged surface.
It also explains why diagnosis needs both tests. The blood test shows whether the immune system is going after the enzyme and gliadin; the biopsy shows whether the villi have actually been flattened. The first is suspicion, the second is the scene itself.
Treatment acts at the start of the chain: take gliadin away, the immune system loses its target, and the later links get a chance to stop. That is why a strict Gluten-Free diet is the treatment itself, not a supporting menu.
Chapter 3
Not the gluten-free fashion
True celiac disease requires strict avoidance of gluten, because the villi get taken apart. In people who avoid gluten because it is fashionable, this enzyme and these antibodies are not at work. Do not merge the two into everyone should drop wheat.
Many people feel unwell after eating wheat but do not have celiac disease (this is often called non-celiac gluten sensitivity). A double-blind trial in such people suggests that what triggers the symptoms is more likely the fructans in wheat (a carbohydrate that is readily fermented in the gut and produces gas) than gluten itself.
The other way around, in a large observational study, people without celiac disease who ate less gluten over the long term did not have a lower risk of coronary heart disease. The researchers also warned that deliberately avoiding gluten may mean eating fewer whole grains along the way.
Many people feel unwell after eating wheat but do not have celiac disease (this is often called non-celiac gluten sensitivity). A double-blind trial in such people suggests that what triggers the symptoms is more likely the fructans in wheat (a carbohydrate that is readily fermented in the gut and produces gas) than gluten itself.
The other way around, in a large observational study, people without celiac disease who ate less gluten over the long term did not have a lower risk of coronary heart disease. The researchers also warned that deliberately avoiding gluten may mean eating fewer whole grains along the way.
Evidence · What two studies do and do not show
Skodje 2018 was a double-blind crossover trial in people who reported non-celiac gluten sensitivity. The same people took gluten, fructans, and a placebo in turn, served as their own controls, and did not know which one they were getting in each round. Symptoms followed the fructans more than the gluten. What it shows: in this group, many people blamed the wrong ingredient. What it cannot show: that gluten is harmless for everyone.Lebwohl 2017 was a prospective cohort of adults without celiac disease, with gluten intake estimated from diet questionnaires. Eating more or less gluten over the long term showed no association with coronary heart disease risk, and the authors warned that deliberately avoiding gluten may mean eating fewer whole grains. This is an observed association, not a trial, so what it answers is cutting gluten bought no heart benefit, not cutting gluten is certainly harmful.
Taken together, the two studies say the same thing. In people without celiac disease, the discomfort may be real, but the cause is more likely fructans than gluten; and avoiding gluten by itself did not buy a heart benefit.
The Gluten-Free trend itself is taken apart in more detail in Gluten-Free. Oats are a separate question: they contain no wheat gluten themselves, and the trouble is cross-contamination during processing plus a minority of people with celiac disease who react to the oat protein itself — see Oats.
Chapter 4
The diet is treatment, not a menu
The Lebwohl 2018 review lists a strict Gluten-Free diet as the established treatment for celiac disease. This story stops at the mechanism and that treatment discipline. It does not give recipes, and it does not replace a gastroenterologist's biopsy and follow-up.
If you suspect you have celiac disease, get tested first. Do not start avoiding gluten on your own and then have your antibodies checked. Once the gluten stops, the immune system has less to attack, the antibodies fall, and the blood test can come back falsely negative.
If you suspect you have celiac disease, get tested first. Do not start avoiding gluten on your own and then have your antibodies checked. Once the gluten stops, the immune system has less to attack, the antibodies fall, and the blood test can come back falsely negative.
References · 5
- Dieterich, W., Ehnis, T., Bauer, M., Donner, P., Volta, U., Riecken, E. O., & Schuppan, D. (1997). Identification of tissue transglutaminase as the autoantigen of celiac disease. Nature Medicine, 3(7), 797-801. 10.1038/nm0797-797
- Molberg, O., McAdam, S. N., Korner, R., Quarsten, H., Kristiansen, C., Madsen, L., Fugger, L., Scott, H., Noren, O., Roepstorff, P., Lundin, K. E., Sjostrom, H., & Sollid, L. M. (1998). Tissue transglutaminase selectively modifies gliadin peptides that are recognized by gut-derived T cells in celiac disease. Nature Medicine, 4(6), 713-717. 10.1038/nm0698-713
- Lebwohl, B., Sanders, D. S., & Green, P. H. R. (2018). Coeliac disease. The Lancet, 391(10115), 70-81. 10.1016/S0140-6736(17)31796-8
- Skodje, G. I., Sarna, V. K., Minelle, I. H., et al. (2018). Fructan, rather than gluten, induces symptoms in patients with self-reported non-celiac gluten sensitivity. Gastroenterology, 154(3), 529-539. 10.1053/j.gastro.2017.10.040
- Lebwohl, B., Cao, Y., Zong, G., et al. (2017). Long term gluten consumption in adults without celiac disease and risk of coronary heart disease: prospective cohort study. BMJ, 357, j1892. 10.1136/bmj.j1892
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