17 The practical implications of implementing elimination and rechallenge

17 the practical implications of implementing

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17 The practical implications of implementing elimination and rechallenge methods should also be considered. There is no clear guidance on what types of elimination diets should be prescribed, the types or quantities of food that should be included in the challenge, or the duration of the challenge. In addition, elimination diets are typically labor- intensive and time-consuming 18 and, being highly restric- tive, they raise issues of nutritional adequacy and can have psychological consequences. Individualized Biomarker-Directed Exclusion of Foods Just as research aiming to identify IBS biomarkers that would assist in the diagnosis of this condition has so far proven inconclusive, 19 so too has research aiming to identify biomarkers of speci fi c food intolerances in IBS. If these occur via the induction of immune or in ammatory mechanisms, strategies could be designed to identify culprit foods based on immune mechanisms. For example, food allergies can be detected using skin-prick tests, which detect allergen-speci fi c IgEs after food challenge. Food allergy presents with a spectrum of clinical syndromes, ranging from anaphylaxis to oral allergy syndrome to food protein-induced enteropa- thy. 20 The overlap of these syndromes with IBS, with or without food intolerances, is ill-de fi ned but probably small, and is largely distinguished on the basis of symptoms. 21 Mostofthe immune-based techniquesfordetection offood allergies appear to have low positive-predictive values. 16 Therefore, the clinical value of these techniques is limited. However, 2 tests have been speci fi cally applied to studies of IBS. The test for food-speci fi c IgG4 can be used to identify foods that might be removed from the diet. However, these antibodiesareoftenfound in healthy people and their levelsor presence correlate poorly with symptoms. This test is, there- fore, not recommended by authorities on food allergy. 22 The May 2015 Food Components and IBS 1159 FOOD AND FUNCTIONAL BOWEL DISEASE
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Table 1. Diets Used by Patients With IBS and Risks of Nutritional Insuf fi ciency Paleolithic Gluten-free Speci fi c carbohydrate Low lactose Low FODMAP Concept Humans have evolved over many hundreds of thousands of years to eat a particular way. Recent changes to human diets, brought on by advances in modern agricultural techniques, have contributed to the onset of diet-related diseases a Avoiding wheat reduces symptoms of IBS in many. This is attributed to gluten in the wheat. Purported mechanisms include damage to the bowel and release of opiate peptides. Reduce di- and poly- saccharide intake as these pass into the large intestine undigested where they are fermented by harmful intestinal microbiota that overgrow to irritate and damage the gut b Lactase de fi ciency leads to lactose malabsorption, which has osmotic and fermentative effects Reduce luminal distension due to osmotic effects of slowly or unabsorbed short-chain carbohydrates Reduce gas and short-chain fatty acid production during their fermentation in the intestine Luminal distension leads to
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