The prevalence of coeliac disease and wheat allergies is estimated at 1% worldwide, yet a recent cross-sectional survey revealed that 7.3% of Australians are restricting their intake of wheat and gluten products.
Are wheat gluten proteins implicated in the pathogenesis of neurological and gastrointestinal health conditions such as schizophrenia, autism spectrum disorder, peripheral neuropathy, intestinal permeability, irritable bowel syndrome and mood disorders? Is the prevalence of pathologies related to wheat increasing?
The current evidence for these questions is presented in a 2016 Nutrition Bulletin review. The findings include:
- Randomised, placebo-controlled, doubled-blind studies demonstrated that wheat allergy is within the range for that of other plant foods.
- The role of gliadin and glutenin proteins in coeliac disease (CD) has been proven conclusively. A perception of increasing prevalence is likely due to increased public awareness and improved detection rates. Subgroups of patients may also suffer from peripheral neuropathy, gluten ataxia and dermatitis herpetiformis.
- Some patients with schizophrenia and autism spectrum disorder have seen improvements after adopting a gluten-free diet. The hypothesis that opioid like gluten peptides enter the bloodstream and cause neurological disruption is not currently supported by scientific studies.
- Non-coeliac gluten sensitivity (NCGS) is a term that defines patients experiencing a syndrome of gastrointestinal, immune and neurological symptoms relating to the consumption of gluten that is not an IgE allergic or autoimmune response. Diagnosis is one of exclusion after allergy or CD is ruled out. The authors believe increasing prevalence rates may be misleading. The current diagnostic criteria are poorly designed and lead to higher reported rates in the published studies. An expert panel has proposed that patients suspected of NCGS follow a gluten-free diet, followed by a double-blinded placebo controlled gluten challenge. A positive result would be a variation of 30% in one or more symptoms.
- In NCGS, irritable bowel syndrome and inflammatory bowel disease there have been significant reductions in symptoms when patients followed a low FODMAPS (fermentable, oligo-, di-, monosaccharides and polyphenols) diet. Relief gained from a gluten-free diet may be due to a lower FODMAPS content rather than the exclusion of gluten.
The public perception that gluten is having a serious impact on health has created a growing market for gluten-free foods. Gluten-free foods are viewed as a “healthy” choice even for those with no symptoms. Grains are traditionally large contributors to the daily nutrient intake. Patients and the wider public need education to ensure vitamin and mineral deficiencies don't develop from eliminating gluten-containing foods from their diets.
The nature of the impact of wheat and gluten on health is complex and not yet completely understood. Further research and better diagnostic criteria are required. There is currently no strong evidence that removing gluten from people’s diets would provide health benefits to the vast majority of the population.
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