What Is Non-Coeliac Gluten Sensitivity

  • Jialu Li Master of Science in Language Sciences (Neuroscience) UCL

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Definition of non-coeliac gluten sensitivity (NCGS) 

Non-coeliac gluten sensitivity (NCGS) is a condition where the intestine is sensitive to gluten, causing specific symptoms, but testing negative for other conditions such as coeliac disease or wheat allergy. NCGS can be difficult to diagnose for a variety of reasons, and a gluten-free diet is the main treatment. The overall prevalence of NCGS is generally unclear but estimated to be 0.5-13% of the population, and it is more common in women than men (6:1).1

What is gluten?

Gluten is a structural protein found in many cereal grains. Humans have been eating gluten-containing foods for centuries.2 Most people don’t react negatively to gluten consumption. There are a group of conditions known as gluten-related disorders (GRDs) where people develop symptoms after consuming gluten.1 These include coeliac disease, wheat allergy, dermatitis herpetiformis, gluten ataxia and non-coeliac gluten sensitivity. The cause of NCGS is less clearly understood than other conditions, such as coeliac disease or wheat allergy.1 

Common sources of gluten in the diet 

Gluten can be found in: 

  • Grains- wheat, barley, and rye
  •  Processed foods- bread, cereals, pasta, pizza, cakes, and many snacks
  • Many beers 

Diagnosis and testing 

There are several difficulties in making a diagnosis of NCGS:3 

  • NCGS can be very difficult to diagnose because there is no established mechanism or valid biomarker of the disease (no visible damage to the intestine or change on a blood test)
  • Gluten hasn’t been reliably shown to cause the symptoms- it causes symptoms in some studies,4 but in many studies, it is not distinguishable from placebo3
  • There are many other conditions that have similar and overlapping symptoms
  • It is often self-diagnosed by people who find that they feel better after they stop eating gluten. 

A more reliable diagnosis may be attained by consulting a doctor or dietitian. A doctor might decide to rule out other conditions like coeliac and wheat allergy before making a diagnosis. Otherwise, there is a risk that coeliac disease diagnosis could be missed if a gluten-free diet is started without checking for this first. 

A diagnosis would generally be made from a patient recording all the food and drinks in a food diary over a period of time. They would also record their symptoms when they arise. The medical staff would then look for associations between the foods eaten and the symptoms recorded. This requires a high degree of compliance from the patients in the form of sticking to a diet and recording food intake and symptoms regularly. 

Some attempts have been made to make a standardised criterion to diagnose NCGS (‘The Salerno Experts’ Criteria’ ).5 This involves assessing the response to a gluten-free diet and measuring the effect on patient symptoms of reintroducing gluten, using a symptom severity scale (0-10).5 At least a 30% change in symptoms is required following the introduction of gluten in order to make a diagnosis.5 

Symptoms of non-coeliac gluten sensitivity 

A diagnosis of NCGS will generally be made on the basis of symptoms that arise following gluten consumption and disappear when it is removed. The following symptoms are commonly associated with NCGS:5 

Gastrointestinal symptoms: 

  • Bloating
  • Stomach pain
  • Diarrhoea
  • Nausea

Non-gastrointestinal symptoms: 

Symptoms vary between people and are often associated with other conditions. 

What else could it be? 

One of the main difficulties in diagnosing NCGS is that the common symptoms are similar to several other conditions: 

Coeliac disease

Coeliac disease is a condition where your immune system attacks your intestinal tissue if you eat gluten. This causes damage to the intestine, which impairs its ability to absorb nutrients. It affects roughly 1 in 100 people. It is diagnosed by a blood test looking for coeliac-associated markers in the blood. If this is positive, doctors may also take a biopsy of the small intestine to look for signs of damage to the wall. In coeliac disease, many of the finger-like projections (villi) in the intestine can be damaged. The consequence of long-term damage to the intestinal wall is that nutrients can’t be absorbed properly, which can lead to nutrient deficiencies. It could be that symptoms a patient has are a sign of early-stage coeliac disease. The treatment for coeliac disease is a strict gluten-free diet. Many people with coeliac need to avoid foods that could possibly have been contaminated with gluten to avoid flare-ups. Symptoms are similar to NCGS and include bloating, stomach pain, diarrhoea and tiredness.

Wheat allergy

Wheat allergy is an allergic reaction to foods containing wheat. Symptoms often develop minutes or hours after eating wheat and include itching or swelling around the mouth and difficulty breathing. It is diagnosed by a skin test where a wheat sample is pricked onto your skin, and a rash or itch will develop if it is positive. Treatments are to avoid wheat proteins and use antihistamines to reduce symptoms.

Irritable bowel syndrome (IBS)

Irritable bowel syndrome (IBS) is a condition that has very similar symptoms to NCGS- abdominal pain, bloating and change in bowel habits (diarrhoea or constipation). Symptoms often ‘flare up’ for a period of time. People with IBS often feel better once they remove certain foods and drinks from their diet. For many people, removing a certain group of foods known as the FODMAPs improves their symptoms.6 These are Fermentable Oligo-, Di-, Monosaccharides, and Polyols. These are foods that are not always easily digested, so they sit in the intestine and ferment with bacteria to produce unpleasant IBS symptoms. There is some debate about whether NCGS is actually IBS. One FODMAP (fructan) is found in gluten-containing foods, and it may be this that causes the symptoms in some people, not the gluten.7

Managing non-coeliac gluten sensitivity

Gluten-free diet 

NGCD is generally managed by following a gluten-free diet with the aim of reducing symptoms. The number of people who don’t eat gluten in their diet has increased in the past few years. Many shops now stock gluten-free alternatives such as gluten-free bread, pasta, and pizzas. Unfortunately, these can be more expensive than gluten-containing foods. It is also possible to order gluten-free alternatives in many restaurants. The range of gluten-free alternatives will vary between regions and countries. Unfortunately, many people find that gluten-free products don’t taste as nice as gluten-containing products. 

It should be noted that not all products can guarantee that they are completely free of gluten contamination. For example, some porridge oats don’t contain gluten, but they might be made in the same factory as other gluten-containing cereals. This would generally be more of a problem for people with serious NCGS or coeliac disease. 

Risks associated with avoiding gluten 

As there is nothing inherently wrong with eating gluten for most people, it should still be consumed as it can be good for people in moderation. There are some risks associated with removing gluten from your diet.

  • It could cause an exacerbation of other symptoms, such as an increase in constipation associated with an overall reduction in fibre.
  • There is a psychological condition called orthorexia nervosa whereby people become increasingly restrictive in their diet without needing to be for health reasons2. This can lead to a decreased quality of life and nutrient deficiencies.2
  • As food is a large part of our shared cultures, eating different things can make people feel more psychologically isolated than they otherwise would. 

 It can be beneficial to work with a doctor and/or a dietician to optimise your diet if necessary. 

Scientific debate around the cause of NCGS 

It is still unclear how NCGS causes its symptoms, as there is no specific marker of disease. In the past few years, more and more people have decided to remove gluten from their diet. There is an ongoing debate in the scientific community about what the cause of NCGS is, with some thinking that it is a part of IBS7 and others thinking that it is more of a placebo effect driven by celebrity fad dieting stories in the media.8 However, it is important to take a patient’s symptoms seriously and not simply dismiss them because of the difficulty of diagnosis or lack of a known cause. 

Ongoing research and potential future developments 

  •  Research is needed to find a specific diagnostic biomarker
  • More studies are needed using larger numbers of patients to distinguish the true prevalence of the condition and determine the actual cause of people’s symptoms


Non-coeliac gluten sensitivity (NCGS) is a condition where the intestine is sensitive to gluten but without the signs of coeliac disease or wheat allergy. NCGS is difficult to diagnose because there is currently no known or accepted biomarker of disease. There are several conditions that have similar symptoms, such as coeliac disease, wheat sensitivity and IBS, and it is important to exclude these if possible. A trained medical practitioner would make a diagnosis after excluding other diseases and by noting an association between symptoms and gluten consumption from a food diary. The most common symptoms of NCGS are abdominal pain, bloating, diarrhoea, and nausea, and some people also have depression, brain fog, tiredness and muscle pain. The main treatment for NCGS is a gluten-free diet. More research is needed on this condition to improve diagnosis and distinguish it from other diseases. It is advised to speak with a trained medical practitioner to get an accurate diagnosis and effective treatment.


  1. Taraghikhah N, Ashtari S, Asri N, Shahbazkhani B, Al-Dulaimi D, Rostami-Nejad M, et al. An updated overview of spectrum of gluten-related disorders: Clinical and diagnostic aspects. BMC Gastroenterology. 2020. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7409416/
  2. Aljada B, Zohni A, El-Matary W. The gluten-free diet for celiac disease and beyond. Nutrients. 2021. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8625243/
  3. Reese I, Schäfer C, Kleine-Tebbe J, Ahrens B, Bachmann O, Ballmer-Weber B, et al. Non-celiac gluten/wheat sensitivity (NCGS)—a currently undefined disorder without validated diagnostic criteria and of unknown prevalence. Allergo J Int. 2018;https://link.springer.com/article/10.1007/s40629-018-0070-2
  4. Biesiekierski JR, Newnham ED, Irving PM, Barrett JS, Haines M, Doecke JD, et al. Gluten Causes gastrointestinal symptoms in subjects without celiac disease: A double-blind randomized placebo-controlled trial. Am J Gastroenterol. 2011;https://pubmed.ncbi.nlm.nih.gov/21224837/
  5. Catassi C, Elli L, Bonaz B, Bouma G, Carroccio A, Castillejo G, et al. Diagnosis of non-celiac gluten sensitivity (NCGS): The salerno experts’ criteria. Nutrients. 2015;https://www.mdpi.com/2072-6643/7/6/4966
  6. Black CJ, Staudacher HM, Ford AC. Efficacy of a low FODMAP diet in irritable bowel syndrome: Systematic review and network meta-analysis. Gut. 2021.https://eprints.whiterose.ac.uk/182000/
  7. Skodje GI, Sarna VK, Minelle IH, Rolfsen KL, Muir JG, Gibson PR, et al. Fructan, Rather Than Gluten, Induces Symptoms in Patients With Self-Reported Non-Celiac Gluten Sensitivity. Gastroenterology. 2018; https://www.gastrojournal.org/article/S0016-5085(17)36302-3/fulltext?referrer=https%3A%2F%2Fpubmed.ncbi.nlm.nih.gov%2F
  8. Jones AL. The gluten-free diet: Fad or necessity? Diabetes Spectrum. 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5439366/

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Doctor of Philosophy - PhD, Oncology and Cancer Biology, University of Liverpool

Harvey obtained a Master of Research degree in Translational Medicine from the University of Liverpool. Subsequently, he earned a Doctorate of Philosophy for his study on the efficacy of chemotherapy drugs on 3D colon cancer models. This academic background provided Harvey with a deep understanding of the complexities of cancer research, particularly concerning the development of new treatment approaches.

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