Non-coeliac gluten sensitivity: symptoms, how it is assessed and what to do

Non-coeliac gluten sensitivity, often shortened to NCGS, is the term used when someone has symptoms similar to those of coeliac disease after eating foods containing wheat, barley or rye, but tests show they do not have coeliac disease and they do not have a wheat allergy. Coeliac UK describes it as a condition being recognised in many countries and says it is a new area in which more research is needed to understand who is at risk.

The NHS describes gluten as a protein found in wheat, barley and rye. In coeliac disease the immune system mistakes substances inside gluten as a threat and attacks them, damaging the surface of the small bowel. In NCGS, Coeliac UK says it is not clear how the immune system might be involved, because no antibodies are produced and there does not appear to be damage to the gut lining.

Some researchers prefer the name non-coeliac wheat sensitivity. A 2019 review in the journal Medicina points out that components of wheat other than gluten may contribute to symptoms, which is why the label itself is still debated.

Three separate problems can look alike from the outside, and telling them apart matters because each one is handled differently. Coeliac UK sets out the differences as follows.

Because NCGS is defined by exclusion, the symptom picture is broad. A 2019 review of the topic reports that the digestive symptoms overlap with irritable bowel syndrome, and that some people also describe symptoms outside the gut. Among those, tiredness, headache and anxiety were the most commonly reported in the studies it summarised. The review also notes that because the symptoms are vague or mimic other medical conditions, the diagnostic process can be long and complex.

The NHS lists a range of gut symptoms for coeliac disease, and these are also the kind of complaints people with suspected NCGS describe. They are not specific to any one condition.

• Bloating and a swollen tummy.

• Tummy pain or cramps.

• Diarrhoea, constipation or a mixture of both.

• Wind (flatulence) and indigestion.

• Tiredness or low energy.

• Headache or a foggy feeling.

The most important practical point is the order of events. Coeliac UK says that if you have symptoms when eating foods containing wheat, barley, rye or oats, it is important to rule out coeliac disease first, and that it does not recommend trying a gluten-free diet as a first option. The reason is that cutting out gluten beforehand can stop the coeliac blood test from giving an accurate result.

The NHS says that routine testing for coeliac disease is not done in England, and testing is usually recommended for people who have symptoms or an increased risk, such as a family history. It notes that coeliac disease affects at least 1 in every 100 people in the UK and that milder cases may go undiagnosed or be mistaken for irritable bowel syndrome. People with type 1 diabetes, autoimmune thyroid disease, Down’s syndrome and Turner syndrome are named as having a higher risk.

Staying on a normal, gluten-containing diet until the test has been done is therefore the standard advice. If you have already stopped gluten, a GP or dietitian can explain how to reintroduce it safely for testing.

Coeliac UK says that if the test for coeliac disease is negative and other causes of symptoms have been ruled out, you might wish to discuss the possibility of NCGS with your healthcare team. Some researchers define it as an improvement in symptoms on a gluten-free diet, but a definitive diagnosis remains challenging.

The 2019 review describes the Salerno experts’ criteria, published in 2015, as the only accessible recommendations for diagnosis. It is a two-step approach: first a structured period on a gluten-free diet, described in the review as a 6-week course with ongoing symptom scoring, and then a measured reintroduction of gluten to see whether symptoms return. The review states that a double-blind, placebo-controlled challenge is the gold standard in research, although a single-blind approach is accepted in clinical practice, and that discussing the move to a gluten-free diet with a dietitian is advised.

The review also draws attention to a nocebo effect, in which expecting a food to cause symptoms can itself produce them. It reports that in one study of people with IBS-like symptoms, almost two-thirds showed this effect after an elimination diet. This is not a suggestion that symptoms are imagined. It is one reason why structured, supervised testing is preferred to informal experiments.

Coeliac UK highlights that when gluten-containing ingredients are removed from the diet, other components are removed too, for example FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) and other non-gluten proteins found in wheat. It is therefore difficult to say whether gluten itself is responsible.

The 2019 review adds that amylase-trypsin inhibitors (ATIs) and FODMAPs have been suggested as possible contributors. FODMAPs are short-chain sugars that are fermented in the bowel, and the review notes that reducing them has been reported to help people with irritable bowel syndrome. For a patient, the practical meaning is that improvement on a wheat-free diet does not by itself prove that gluten was the cause, and a dietitian can help work out which foods actually matter.

There is no cure or approved drug treatment for NCGS in the sources reviewed. The management described is dietary, individualised and ideally supported by a dietitian so that the diet stays balanced. Coeliac UK offers information on following a gluten-free diet for those who need to.

See a GP rather than managing alone if you have unintentional weight loss, ongoing tiredness, or symptoms that are getting worse. The NHS lists unintentional weight loss and tiredness among the features of coeliac disease, and persistent symptoms deserve their own assessment. Children with long-standing digestive symptoms or poor growth should also be seen, because the NHS notes that children with coeliac disease may not grow at the expected rate.

In the NHS, assessment usually starts with a GP, who can arrange coeliac blood tests and consider other causes such as irritable bowel syndrome. Dietitian input is available through NHS referral in some areas and privately elsewhere; a private route can offer faster access to dietetic advice but the testing logic described above is the same.