A 2018 review concluded that although fructan intolerance may play a role in NCGS, it only explains some gastrointestinal symptoms, but not the extradigestive symptoms that people with NCGS may develop, such as neurological disorders, fibromyalgia, psychological disturbances, and dermatitis. FODMAPs cause digestive symptoms when the person is hypersensitive to luminal distension. A 2019 review concluded that wheat fructans can cause certain IBS-like symptoms, such as bloating, but are unlikely to cause immune activation or extra-digestive symptoms. Many people with NCGS report resolution of their symptoms after removing gluten-containing cereals while continue to eat fruits and vegetables with high FODMAPs content. Diagnosis
Absence of reliable biomarkers and the fact that some people do not have digestive symptoms make the recognition and diagnosis of non-celiac gluten sensitivity (NCGS) difficult.Diagnosis is generally performed only by exclusion criteria. NCGS diagnostic recommendations have been established by several consensus conferences. Exclusion of celiac disease and wheat allergy is important because these two conditions also appear in people who experience symptoms similar to those of NCGS, which improve with a gluten withdrawal and worsen after gluten consumption.The onset of NCGS symptoms may be delayed hours to a few days after gluten ingestion, whereas in celiac disease it can take days to weeks. Wheat allergy has a fast onset (from minutes to hours) after the consumption of food containing wheat and can lead to anaphylaxis.The presence of related extraintestinal manifestations has been suggested to be a feature of NCGS.
Sporadic accidental contaminations with gluten can reactivate movement disorders. A part of people with gluten-related neuropathy or ataxia appears not to be able to tolerate even the traces of gluten allowed in most foods labeled as "gluten-free".Whereas celiac disease requires adherence to a strict lifelong gluten-free diet, it is not yet known whether NCGS is a permanent or a transient condition. The results of a 2017 study suggest that NCGS may be a chronic disorder, as is the case with celiac disease. A trial of gluten reintroduction to observe any reaction after one to two years of strict gluten-free diet might be performed.A strict gluten-free diet is effective in most of the neurological disorders associated with NCGS, ameliorating or even resolving the symptoms. It should be started as soon as possible to improve the prognosis. The death of neurons in the cerebellum in ataxia is the result of gluten exposure and is irreversible. Early treatment with a strict gluten-free diet can improve ataxia symptoms and prevent its progression. When dementia has progressed to an advanced degree, the diet has no beneficial effect. Cortical myoclonus appears to be treatment-resistant on both gluten-free diet and immunosuppression. Persistent symptoms
Approximately one third of presumed NCGS patients continue to have symptoms, despite gluten withdrawal. Apart from a possible diagnostic error, there are multiple possible explanations.One reason is poor compliance with gluten withdrawal, whether voluntary and/or involuntary. There may be ingestion of gluten, in the form of cross contamination or food containing hidden sources.