Few dietary topics generate more confusion than gluten. At one end, coeliac disease is a serious autoimmune condition requiring strict lifelong avoidance. At the other, gluten-free eating has become a lifestyle choice for millions with no medical need. Somewhere in between sits non-coeliac gluten sensitivity — real, but poorly understood.
Here’s a clear breakdown of what we actually know.
Coeliac disease: an autoimmune condition
Coeliac disease is a well-characterised autoimmune disorder in which gluten (specifically the gliadin protein in wheat, barley, and rye) triggers an immune response that damages the small intestinal lining — particularly the villi (finger-like projections that absorb nutrients).
Key facts:
- Affects approximately 1% of the population worldwide
- Caused by genetic susceptibility (HLA-DQ2 or DQ8 genes) combined with gluten exposure
- Diagnosed via blood test (tTG-IgA antibodies) and confirmed with intestinal biopsy
- You must be consuming gluten when tested — going gluten-free before testing renders results unreliable
- Even small amounts of gluten (cross-contamination) cause intestinal damage
- Requires strict, permanent gluten-free diet
- Untreated, it causes malabsorption, nutritional deficiencies, and increased risk of complications
Symptoms range widely, which is why coeliac is often missed. Classic presentations include diarrhoea, weight loss, and anaemia. But many people have “silent” or atypical coeliac with symptoms like fatigue, brain fog, joint pain, infertility, or elevated liver enzymes — with minimal digestive symptoms.
Wheat allergy: an IgE-mediated reaction
Distinct from coeliac, wheat allergy is a classic IgE-mediated immune response to wheat proteins (not specifically gluten). Symptoms include hives, swelling, respiratory symptoms, and in severe cases, anaphylaxis. Diagnosis is through skin prick tests or specific IgE blood tests. It primarily affects children and is often outgrown.
Non-coeliac gluten sensitivity (NCGS)
NCGS describes people who experience symptoms when consuming gluten but test negative for coeliac disease and wheat allergy. The condition is real — confirmed in double-blind placebo-controlled studies — but its mechanisms are different and less well understood.
In NCGS:
- No intestinal villi damage occurs
- The immune pathway is different (innate immunity rather than adaptive)
- Some evidence points to increased intestinal permeability
- Symptoms include bloating, abdominal pain, diarrhoea, brain fog, and fatigue
- Diagnosis is by exclusion: rule out coeliac and wheat allergy, then confirm through symptom response to gluten challenge
The fructan complication: Wheat contains fructans (a type of FODMAP), not just gluten. Multiple studies have found that some people who believe they have gluten sensitivity are actually reacting to fructans. In a 2018 blinded study, participants with self-reported NCGS showed significantly more symptoms on fructan challenge than gluten challenge. This matters because the solutions are different.
How to tell which applies to you
Step 1: Test for coeliac before going gluten-free. Ask your GP for tTG-IgA antibody testing while you’re still consuming gluten-containing foods. If positive, you’ll be referred for intestinal biopsy.
Step 2: If coeliac is excluded, trial gluten-free with careful tracking. Keep a detailed food and symptom journal before and during the trial. Track symptoms, energy, and bowel habits.
Step 3: Consider testing for fructan sensitivity. If you feel better gluten-free, try systematically reintroducing pure gluten sources (gluten powder, or small amounts of pure wheat starch) without fructans. If symptoms return, gluten is likely the issue. If not, fructans may be the culprit — which means a low-FODMAP approach (less restrictive) may work better than full gluten avoidance.
Step 4: Work with a specialist. A gastroenterologist or FODMAP-trained dietitian can guide this process effectively and help you avoid years of unnecessary restriction.
The goal is always to eat as broadly as possible while feeling well — not to eliminate more foods than necessary.
Frequently asked questions
Can I test myself for coeliac disease at home?
No — coeliac disease requires both blood tests (for tTG-IgA antibodies) and intestinal biopsy for definitive diagnosis. Crucially, you must be consuming gluten when tested. Going gluten-free before testing makes results unreliable. See your GP before trialling a gluten-free diet if you suspect coeliac.
Is non-coeliac gluten sensitivity (NCGS) real?
Yes, though it remains controversial and less understood than coeliac disease. Multiple double-blind studies have confirmed that some people experience reproducible symptoms from gluten even without coeliac disease or wheat allergy. The mechanisms are different from coeliac (no intestinal damage, different immune pathways).
Could my 'gluten sensitivity' actually be fructan sensitivity?
Possibly. Wheat contains both gluten and fructans (a type of FODMAP). Some studies suggest that people who report gluten sensitivity may actually be reacting to fructans, not gluten. Testing can help distinguish the two — fructan sensitivity is addressed through low-FODMAP approaches, while true NCGS requires gluten avoidance.
If I feel better gluten-free, should I stay gluten-free?
Only after ruling out coeliac disease through proper testing first (while still consuming gluten). If coeliac is excluded, and a careful reintroduction protocol confirms that gluten specifically (not fructans, not other wheat components) causes symptoms, a gluten-free or gluten-reduced approach is reasonable.