Celiac disease is a lifelong autoimmune condition in which eating gluten triggers an immune attack on the lining of the small intestine, flattening the villi that absorb nutrients. It is not a wheat allergy, and unlike non-celiac gluten sensitivity the damage is immune-mediated and visible under a microscope. Around one person in a hundred has it in most screened populations, and many are undiagnosed, because it ranges from diarrhea and weight loss to nothing beyond stubborn anemia. The fuller reference is the Celiac disease entry in the Smart Longevity glossary.
What it measures
Celiac disease is a diagnosis rather than a single number, assembled from blood antibodies, what the gut lining looks like, and what happens once gluten is removed. The first-line blood test is tissue transglutaminase IgA (tTG-IgA), drawn with total IgA. Total IgA matters because people with selective IgA deficiency make no IgA antibodies, so their tTG-IgA reads negative however damaged the gut is; IgG tests are used instead. Endomysial antibodies (EMA) confirm, and an upper endoscopy with several duodenal biopsies looks for the lesion itself.
HLA typing for DQ2 and DQ8 works only in reverse: nearly everyone with celiac disease carries one, but so does a large minority of everyone else, so a negative result rules the diagnosis out while a positive one proves nothing. One practical point decides whether any of it works: these tests need an active immune response, so you must still be eating gluten when they are done.
Typical values
There is no universal cut-off to quote: assays are calibrated differently by each manufacturer, so a result means something only against your own report’s reference interval.
| Test | What the report shows | How it is read |
|---|---|---|
| tTG-IgA | A number next to the lab’s upper limit of normal | Main screening test; labs are not interchangeable |
| Total IgA | A concentration with an age-specific range | Low or absent means IgA tests cannot be trusted |
| EMA-IgA | Positive or negative | Very specific; confirms a positive tTG-IgA |
| Duodenal biopsy | A Marsh grade, 0 through 3 | Grade 3 is villous atrophy, the defining lesion |
Some guidelines allow a no-biopsy diagnosis in children whose tTG-IgA is at least ten times their lab’s upper limit of normal with a positive EMA on a second sample: a multiple of the local cut-off, not a fixed number.
Why it matters for longevity
The damaged surface is where iron, folate, calcium and fat-soluble vitamins are taken up, so untreated celiac disease often shows up first as deficiency. Iron is the classic case, because duodenal villi are the main site of Iron absorption, and an anemia that will not respond to iron tablets is a standard reason to test for it.
Over years, poor calcium and vitamin D uptake plus inflammation lower bone density, and adults diagnosed late have more Osteoporosis and more fractures. The condition also clusters with other autoimmune disease, particularly type 1 diabetes and autoimmune thyroid disease. Cohort studies report modestly raised all-cause mortality, concentrated in people whose villous atrophy persists on a supposedly gluten-free diet. Those are observational associations, but they point one way: risk tracks how well the lining heals.
What changes it
One thing changes it, and changes it completely: a strict, lifelong gluten-free diet. No wheat, rye or barley, including spelt and malt, and watch for cross-contamination in shared toasters, fryers and flour dust. Most people tolerate pure oats, but commodity oats are often contaminated in the mill, so only certified gluten-free oats count. Check medications too, where wheat starch is a common filler.
Antibody levels usually fall over months on the diet and are used to track adherence. Healing of the lining is slower and in adults sometimes incomplete, so follow-up matters more than early relief of symptoms. Ask for baseline checks of iron stores, B12, folate, vitamin D and bone density, and work with a dietitian. The rest is not under your control: the genetic susceptibility is fixed.
Related reading
- How to Support Gut Health and Your Microbiome
- Fiber, the Microbiome, and Longevity
- How to Strengthen Bones and Prevent Osteoporosis
- Osteoporosis
Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.