The effect of gluten in adolescents and young adults with gastrointestinal symptoms: a blinded randomised cross-over trial

Molecular Triggers of Non-celiac Wheat Sensitivity: A Scoping Review and Analysis

INTRODUCTION

Nonceliac wheat sensitivity (NCWS) is characterized by a symptomatic response to the ingestion of foods containing wheat and related cereal grains in the absence of celiac disease or wheat allergy. Despite efforts to identify the constituent component(s) of wheat responsible for triggering NCWS, no consensus has emerged, leading to competing claims. We aimed to systematically evaluate the literature and provide an evidence-based conclusion on the contribution of specific wheat components to NCWS.

METHODS

A comprehensive search of multiple bibliographic databases was conducted, focusing on primary research. Data were systematically analyzed, and methodological gaps were identified.

RESULTS

The search identified 175 unique citations, revealing 3 categories of compounds frequently considered as potential triggers of NCWS: gluten, fermentable carbohydrates, and amylase/trypsin inhibitors (ATIs). Among 16 double-blind placebo-controlled studies, 8 reported a greater symptomatic response to gluten than the control. Only 1 controlled study examined fermentable carbohydrates, finding a modest effect, but the tested carbohydrates were not derived from wheat. No eligible studies assessed ATIs or other wheat-related compounds as potential NCWS triggers. Across studies, significant limitations and methodological inconsistencies were noted, particularly in participant selection, challenge protocols, and data reporting.

DISCUSSION

Gluten is the most extensively investigated wheat component linked to NCWS, but evidence for its role is inconsistent and undermined by methodological limitations. No direct evidence currently links wheat fermentable carbohydrates, ATIs, or other components to NCWS symptoms. The existing evidence is insufficient to justify restricting specific components of wheat in the management of NCWS. Future studies must overcome the identified gaps to rigorously investigate the role of wheat and related cereals in NCWS, with the potential to advance diagnosis and treatment.

A gluten-free diet for endometriosis patients lacks evidence to recommend it

Endometriosis is an estrogen-dependent chronic disease characterized by the presence of endometriumlike tissue outside the uterus and is often associated with symptoms, such as dysmenorrhea, dysuria, dyschezia, chronic pelvic pain, and infertility. Moreover, women diagnosed with endometriosis can report gastrointestinal symptoms, including bloating, constipation or diarrhea, and abdominal cramping, which can be associated with irritable bowel syndrome and can result in the misdiagnosis of endometriosis as irritable bowel syndrome at first. Treatment usually involves hormonal therapy, pain management, surgery, and/or assisted reproductive techniques in case of infertility. Nonetheless, these treatment methods can be insufficient for alleviating symptoms or can have unacceptable side effects, leading to noncompliance. Therefore, women often apply self-management strategies, including dietary interventions. One of the diets frequently suggested as a tool to manage endometriosis-related symptoms on social media and patient forums is a gluten-free diet. Although a gluten-free diet has been proven effective in managing nonceliac wheat sensitivity or celiac disease, its effectiveness in endometriosis remains uncertain. The Nurses' Health Study II found it unlikely that gluten intake was a strong factor in endometriosis etiology and symptomatology. To the best of our knowledge, the most frequently cited and sole published intervention study on the efficacy of a gluten-free diet for endometriosis has several important limiting factors, including the absence of a control group. In addition, gluten consumption is highly susceptible to a placebo effect and a nocebo effect, where women might experience symptom relief after eliminating gluten and return of symptoms after they consume gluten again, solely because they believe that gluten is bad for them. Despite the inverse association between body mass index and endometriosis and between a gluten-free diet and increased body mass index, this is an association, and no causality was proven. In addition, other factors should be taken into consideration. Of note, a gluten-free diet is expensive, has limited availability, and has a significant effect on quality of life. Moreover, without proper dietary guidance, it may adversely affect the gastrointestinal microbiome. Therefore, scientifically substantiated advice regarding the use of a gluten-free diet for endometriosis-related symptoms is currently not available, and a gluten-free diet should be discouraged unless there is an additional diagnosis of nonceliac wheat sensitivity or celiac disease.

Two randomized crossover multicenter studies investigating gastrointestinal symptoms after bread consumption in individuals with noncoeliac wheat sensitivity: do wheat species and fermentation type matter?

BACKGROUND

Many individuals reduce their bread intake because they believe wheat causes their gastrointestinal (GI) symptoms. Different wheat species and processing methods may affect these responses.

OBJECTIVES

We investigated the effects of 6 different bread types (prepared from 3 wheat species and 2 fermentation conditions) on GI symptoms in individuals with self-reported noncoeliac wheat sensitivity (NCWS).

METHODS

Two parallel, randomized, double-blind, crossover, multicenter studies were conducted. NCWS individuals, in whom coeliac disease and wheat allergy were ruled out, received 5 slices of yeast fermented (YF) (study A, n = 20) or sourdough fermented (SF) (study B, n = 20) bread made of bread wheat, spelt, or emmer in a randomized order on 3 separate test days. Each test day was preceded by a run-in period of 3 d of a symptom-free diet and separated by a wash-out period of ≥7 d. GI symptoms were evaluated by change in symptom score (test day minus average of the 3-d run-in period) on a 0-100 mm visual analogue scale (ΔVAS), comparing medians using the Friedman test. Responders were defined as an increase in ΔVAS of ≥15 mm for overall GI symptoms, abdominal discomfort, abdominal pain, bloating, and/or flatulence.

RESULTS

GI symptoms did not differ significantly between breads of different grains [YF bread wheat median ΔVAS 10.4 mm (IQR 0.0-17.8 mm), spelt 4.9 mm (-7.6 to 9.4 mm), emmer 11.0 mm (0.0-21.3 mm), P = 0.267; SF bread wheat 10.5 mm (-3.1 to 31.5 mm), spelt 11.3 mm (0.0-15.3 mm), emmer 4.0 mm (-2.9 to 9.3 mm), P = 0.144]. The number of responders was also comparable for both YF (6 to wheat, 5 to spelt, and 7 to emmer, P = 0.761) and SF breads (9 to wheat, 7 to spelt, and 8 to emmer, P = 0.761).

CONCLUSIONS

The majority of NCWS individuals experienced some GI symptoms for ≥1 of the breads, but on a group level, no differences were found between different grains for either YF or SF breads.

CLINICAL TRIAL REGISTRY

clinicaltrials.gov, NCT04084470 (https://classic.

CLINICALTRIALS

gov/ct2/show/NCT04084470).

Home-Based Double-Blind, Placebo-Controlled Challenges for Diagnosis of Delayed Gluten/Milk Hypersensitivity in Children

BACKGROUND

Delayed hypersensitivity to gluten and milk protein is frequently reported but may be difficult to diagnose.

OBJECTIVE

We aimed to explore if a method of home-based double-blind placebo-controlled food challenges (H-FC) can identify and reduce unnecessary elimination diets in children.

METHODS

We included 73 of 92 children aged 1 to 17 years referred to a tertiary allergy clinic from 2011 to 2021 due to self-reported, delayed symptoms to gluten or milk. The children were randomized to H-FC, receiving gluten/milk protein or placebo for 5 to 7 days in a double-blind crossover manner, separated by 3 washout weeks. Patients/parents recorded symptoms using standardized forms. Two crossover periods were used from 2011 to 2016 and 3 periods from 2017 to 2021. A positive challenge required significantly more symptoms during the active period versus the placebo period. After the challenge, reintroduction of milk/gluten was assessed by a follow-up interview. The primary outcome was the proportion of children with a positive challenge.

RESULTS

The children, with a mean age of 11 years, had followed a strict gluten-free or milk-protein-free diet for a median duration of 24 months (range: 3-180 months). A positive challenge was observed in 18 of 73 children (25%), more often using 2 (35%) compared with 3 challenge periods (12%). At follow-up, 44 of 55 (80%) children with a negative challenge had successfully reintroduced milk/gluten.

CONCLUSIONS

H-FC may be an effective method in avoiding unnecessary elimination diets in children. Only 25% of the challenges were positive, and 80% of the children with negative challenges succeeded in reintroducing the food. Three challenge periods may be necessary to reduce false-positive outcomes.

The effect of expectancy versus actual gluten intake on gastrointestinal and extra-intestinal symptoms in non-coeliac gluten sensitivity: a randomised, double-blind, placebo-controlled, international, multicentre study

BACKGROUND

Many individuals without coeliac disease or wheat allergy reduce their gluten intake because they believe that gluten causes their gastrointestinal symptoms. Symptoms could be affected by negative expectancy. Therefore, we aimed to investigate the effects of expectancy versus actual gluten intake on symptoms in people with non-coeliac gluten sensitivity (NCGS).

METHODS

This randomised, double-blind, placebo-controlled, international, multicentre study was done at the University of Leeds (Leeds, UK), Maastricht University (Maastricht, the Netherlands), and Wageningen University and Research (Wageningen, the Netherlands). People aged 18-70 years with self-reported NCGS (ie, gastrointestinal symptoms within 8 h of gluten consumption) without coeliac disease and wheat allergy were recruited. Participants had to follow a gluten-free or gluten-restricted diet for at least 1 week before (and throughout) study participation and had to be asymptomatic or mildly symptomatic (overall gastrointestinal symptom score ≤30 mm on the Visual Analogue Scale [VAS]) while on the diet. Participants were randomly assigned (1:1:1:1; blocks of eight; stratified by site and gender) to one of four groups based on the expectation to consume gluten-containing (E+) or gluten-free (E-) oat bread for breakfast and lunch (two slices each) and actual intake of gluten-containing (G+) or gluten-free (G-) oat bread. Participants, investigators, and those assessing outcomes were masked to the actual gluten assignment, and participants were also masked to the expectancy part of the study. The primary outcome was overall gastrointestinal symptom score on the VAS, which was measured at and corrected for baseline (before breakfast) and hourly for 8 h, with lunch served after 4 h, and analysed per-protocol. Safety analysis included all participants incorporated in the per-protocol analysis. The study is registered at ClinicalTrials.gov, NCT05779358, and has ended.

FINDINGS

Between Oct 19, 2018, and Feb 14, 2022, 165 people were screened and 84 were randomly assigned to E+G+ (n=21), E+G- (n=21), E-G+ (n=20), or E-G- (n=22). One person in the E+G+ group was excluded due to not following test day instructions, leaving 83 participants in the per-protocol analysis. Median age was 27·0 years (IQR 21·0-45·0), 71 (86%) of 83 people were women, and 12 (14%) were men. Mean overall gastrointestinal symptom score was significantly higher for E+G+ (16·6 mm [95% CI 13·1 to 20·0]) than for E-G+ (6·9 mm [3·5 to 10·4]; difference 9·6 mm [95% CI 3·0 to 16·2], p=0·0010) and E-G- (7·4 mm [4·2 to 10·7]; difference 9·1 mm [2·7 to 15·6], p=0·0016), but not for E+G- (11·7 mm [8·3 to 15·1]; difference 4·9 mm [-1·7 to 11·5], p=0·28). There was no difference between E+G- and E-G+ (difference 4·7 mm [-1·8 to 11·3], p=0·33), E+G- and E-G- (difference 4·2 mm [-2·2 to 10·7], p=0·47), and E-G+ and E-G- (difference -0·5 mm [-7·0 to 5·9], p=1·0). Adverse events were reported by two participants in the E+G- group (itching jaw [n=1]; feeling lightheaded and stomach rumbling [n=1]) and one participant in the E-G+ group (vomiting).

INTERPRETATION

The combination of expectancy and actual gluten intake had the largest effect on gastrointestinal symptoms, reflecting a nocebo effect, although an additional effect of gluten cannot be ruled out. Our results necessitate further research into the possible involvement of the gut-brain interaction in NCGS.

FUNDING

Government of the Netherlands Topsector Agri & Food Top Consortium for Knowledge and Innovation, AB Mauri Global Bakery Ingredients, Baking Industry Research Trust, Borgesius-Albert Heijn, CSM Innovation Centre, the International Maize and Wheat Improvement Center (CIMMYT), DSM Food Specialties, Fazer, Healthgrain Forum, the International Association for Cereal Science and Technology, the International Wheat Gluten Association, Lantmännen, Mondelez International, Nederlands Bakkerij Centrum, Nutrition & Santé, Puratos, Rademaker, Sonneveld Group, and Zeelandia HJ Doeleman.

Effects of gluten on dyspeptic symptoms: a systematic review and meta-analysis of clinical trials

CONTEXT

Research on the effects of gluten on dyspeptic symptoms has shown conflicting results.

OBJECTIVE

The aim of this systematic review and meta-analysis of clinical trials was to assess the effects of gluten on dyspeptic symptoms.

DATA SOURCES

A systematic search of the PubMed, ISI Web of Science, Scopus, Cochrane, and Embase online databases was performed up to May 2022.

DATA EXTRACTION

Randomized controlled trials (RCTs) and non-RCTs that examined the impact of a gluten-free diet, a low-gluten diet, or a gluten challenge on dyspeptic symptoms, including early satiety, epigastric pain, bloating, and nausea, were selected independently by 2 authors. The GRADE (Grading of Recommendations Assessment, Development, and Evaluation) framework was used to assess the certainty of the evidence. Results were pooled using a random-effects model and expressed as weighted mean differences (WMDs) and 95%CIs.

DATA ANALYSIS

Of the 7641 citations retrieved, 27 articles (18 RCTs and 9 non-RCTs) were included in the systematic review. Of those, 5 RCTs were eligible for the meta-analysis. The pooled results indicated that gluten challenge significantly increased the severity of bloating (WMD = 0.67; 95%CI, 0.37-0.97; I2 = 81.8%; n = 6), early satiety (WMD = 0.91; 95%CI, 0.58-1.23; I2 = 27.2%; n = 5), and epigastric pain (WMD = 0.46; 95%CI, 0.17-0.75; I2 = 65.8%; n = 6). However, the effect of gluten challenge on the severity of nausea (WMD = 0.13; 95%CI, -0.17 to 0.43; I2 = 0.0%, n = 5) was nonsignificant.

CONCLUSION

Gluten challenge significantly worsened dyspeptic symptoms, including bloating, early satiety, and epigastric pain, but did not affect nausea. These findings suggest that gluten restriction could be efficient in reducing dyspeptic symptoms. Well-designed large RCTs recruiting homogenous groups of patients with functional dyspepsia are needed to clarify the effectiveness of gluten restriction on dyspeptic symptoms.

Diet associations in endometriosis: a critical narrative assessment with special reference to gluten

Endometriosis is characterized by the presence of endometrium-like tissue outside the uterus. The etiology remains largely unknown. Despite adequate treatment, patients can still experience symptoms or side effects resulting in therapy incompliance and in self-management strategies such as dietary measures is increasing. A gluten free diet is thought to be contributory in reducing endometriosis-related pain, thereby optimizing quality of life. However, data is conflicting and currently provides no evidence for causality. This narrative review aims to put the effect of dietary self-management strategies on endometriosis in a balanced perspective, especially the effect of gluten and a gluten free diet. Several studies have found a strong overlap in symptoms, metabolic and immune responses associated with endometriosis and those associated with celiac disease, ulcerative colitis, Crohn's disease, irritable bowel syndrome and non-celiac wheat sensitivity. However, it remains unclear whether these diseases and/or disorders are causal to an increased risk of endometriosis. Some studies have found a positive effect on the risk of endometriosis, endometriosis-related symptoms and quality of life (QoL) when women either avoided certain nutrients or foods, or applied a specific nutrient supplementation. This includes the avoidance of red meat, an increasing intake of foods rich in anti-oxidants, omega-3, micronutrients and dietary fibers (e.g., fruit, vegetables) and the appliance of a gluten free diet. However, data from the available studies were generally graded of low quality and it was noted that placebo and/or nocebo effects influenced the reported positive effects. In addition, such effects were no longer seen when adjusting for confounders such as overweight, when a translation was made from in vitro to in vivo, or when the nutrients were not supplemented as isolated sources but as part of a mixed daily diet. Finally, some studies showed that long-term adherence to a gluten free diet is often associated with an impaired diet quality and nutrient intake, leading to negative health outcomes and reduced QoL. Concluding, scientific evidence on the efficacy of dietary interventions on well-defined clinical endpoints of endometriosis is lacking and recommending a gluten free diet to women solely diagnosed with endometriosis should therefore not be advised.

Does sourdough bread provide clinically relevant health benefits?

During the last decade, scientific interest in and consumer attention to sourdough fermentation in bread making has increased. On the one hand, this technology may favorably impact product quality, including flavor and shelf-life of bakery products; on the other hand, some cereal components, especially in wheat and rye, which are known to cause adverse reactions in a small subset of the population, can be partially modified or degraded. The latter potentially reduces their harmful effects, but depends strongly on the composition of sourdough microbiota, processing conditions and the resulting acidification. Tolerability, nutritional composition, potential health effects and consumer acceptance of sourdough bread are often suggested to be superior compared to yeast-leavened bread. However, the advantages of sourdough fermentation claimed in many publications rely mostly on data from chemical and in vitro analyzes, which raises questions about the actual impact on human nutrition. This review focuses on grain components, which may cause adverse effects in humans and the effect of sourdough microbiota on their structure, quantity and biological properties. Furthermore, presumed benefits of secondary metabolites and reduction of contaminants are discussed. The benefits claimed deriving from in vitro and in vivo experiments will be evaluated across a broader spectrum in terms of clinically relevant effects on human health. Accordingly, this critical review aims to contribute to a better understanding of the extent to which sourdough bread may result in measurable health benefits in humans.

Nonceliac gluten sensitivity

PURPOSE OF REVIEW

To describe recent advances on nonceliac gluten sensitivity (NCGS), a recently described disorder characterized by variable symptoms and frequent irritable bowel syndrome (IBS)-like manifestations.

RECENT FINDINGS

The recent description of disease-triggering wheat components other than gluten, such as fructans and amylase-trypsin inhibitors (ATIs), definitely suggests that nonceliac wheat sensitivity (NCWS) is a better 'umbrella' terminology than NCGS. Self-reported NCWS is very common worldwide, particularly in patients seen at the gastroenterology clinic, but many of these diagnoses are not confirmed by standard clinical criteria. A biomarker of NCWS is still lacking, however, subtle histological features at the small intestinal biopsy may facilitate diagnosis. Treatment of NCWS is based on the gluten-free diet (GFD). The GFD has proven to be an effective treatment of a significant proportion of NCWS-related IBS patients. Dietary therapies for IBS, including the GFD, should be offered by dietitians who first assess dietary triggers and then tailor the intervention according to patient choice. Pioneer studies are under way to test the therapeutic efficacy of supplemental gluten-digesting enzyme preparations in patients with NCWS.

SUMMARY

Recent studies highlight interesting pathophysiological and clinical features of NCWS. Many questions remain, however, unanswered, such as the epidemiology, a biomarker(s), and the natural history of this clinical entity.