Gluten Sensitivity: How to Detect It Without Getting It Wrong

Gluten sensitivity, coeliac disease, wheat allergy: three very different realities

"Gluten sensitivity" is often spoken about as though it were self-evident, yet the term actually covers three distinct conditions. Coeliac disease is a serious autoimmune condition in which gluten triggers the destruction of intestinal villi. Wheat allergy involves a classical immune response mediated by IgE antibodies. And then there is non-coeliac gluten sensitivity (NCGS) — the hardest of the three to pin down.

NCGS is characterised by digestive and extra-digestive symptoms (bloating, abdominal pain, fatigue, headaches) that appear after gluten ingestion in people who have already been ruled out for coeliac disease and wheat allergy. Its biological mechanisms remain poorly understood: current thinking points to activation of the innate immune system, increased intestinal permeability (the so-called leaky gut), gut microbiome dysbiosis, and low-grade inflammation — all of this without any detectable specific antibodies. In other words, there is no simple biological marker to identify it.

Its prevalence is estimated at between 0.6% and 13% of the population depending on the study — a very wide range that illustrates just how difficult this syndrome is to measure.

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Gluten and the gut microbiome: a complex relationship

What we do know is that gluten — found in wheat, barley, and rye in the form of proteins called prolamins (including gliadin) — can disrupt the intestinal microbial balance. It reduces bacterial diversity and damages the gut lining, promoting chronic low-grade inflammation.

Paradoxically, long-term gluten-free diets also reduce microbial diversity. This finding, drawn from several recent reviews, is fundamental: cutting out gluten without good reason is not without consequence for your microbiome.

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Symptoms that should raise concern

NCGS does not always present in an obvious way. Here are the signs worth taking seriously:

• Digestive symptoms: bloating, abdominal pain or cramps, diarrhoea or constipation, irregular bowel habits
• Extra-digestive symptoms: persistent fatigue, headaches, brain fog, joint or muscle pain, skin rashes
• Temporal link: symptoms appearing within hours of consuming gluten, with improvement upon its removal

The difficulty is that these symptoms are common to many other conditions — irritable bowel syndrome (IBS), lactose intolerance, sensitivity to FODMAPs — which makes self-diagnosis particularly risky.

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The recommended detection protocol: step by step

Current guidelines (including the Rome IV consensus and guidance from the American Gastroenterological Association) are clear: NCGS is diagnosed by exclusion, following a rigorous process.

Step 1 — First rule out coeliac disease and wheat allergy Before anything else, your GP will arrange a tissue transglutaminase IgA serology test (and, if positive, an intestinal biopsy) to exclude coeliac disease, along with specific IgE testing to rule out wheat allergy. Crucially, these tests must be carried out before starting any gluten-free diet, as doing otherwise risks false negatives.

Step 2 — Strict gluten elimination (at least 6 weeks) Under medical or dietetic supervision, you remove all gluten from your diet: bread, pasta, biscuits, and also hidden sources (shop-bought sauces, processed meats, ready meals). This phase must be thorough to yield meaningful results.

Step 3 — Controlled reintroduction This is the crucial step. If your symptoms have clearly improved during the elimination phase, the gradual reintroduction of gluten — always under supervision — should trigger a return of symptoms in order to confirm a causal link. In the absence of a validated biological test, this remains the diagnostic gold standard.

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What not to do

• Self-diagnose and adopt a gluten-free diet without prior medical assessment — you could miss an undiagnosed coeliac disease and risk nutritional deficiencies in the process.
• Overlook other factors: ultra-processed foods (containing additives such as carboxymethylcellulose or polysorbate 80) also damage the gut lining and can mimic gluten sensitivity.
• Forget the microbiome: a diet rich in prebiotic fibre (pulses, fruit, vegetables), polyphenols (berries, green tea, cocoa), and fermented foods (kefir, sauerkraut) supports the intestinal barrier through butyrate production — which can, in some cases, ease symptoms that have been wrongly attributed to gluten.

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In summary: caution and method

Non-coeliac gluten sensitivity is real, and its effects on the gut microbiome and intestinal inflammation are genuine. But it is precisely because its mechanisms are complex that it deserves a serious diagnostic approach — not an elimination diet decided alone after a quick internet search. A gastroenterologist or a dietitian specialising in gut health is your best ally for targeting the right problem and avoiding unnecessarily depriving your microbiome of what it needs.