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Diet is a cornerstone in the management of irritable bowel syndrome (IBS). There is evidence of efficacy across the spectrum of dietary management strategies, including some supplements (eg, specific fibres), foods, and whole diets (eg, a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols [known as the low-FODMAP diet]). Whole-diet interventions, in particular those that restrict intake, can be challenging to deliver effectively and safely. Factors to consider include patient demographics, food cost and availability, and the acceptability of dietary management and its impact on food-related quality of life. There is concern regarding a potential role of restrictive whole-diet interventions in eating disorder risk. Optimal approaches to delivering dietary management in the health-care setting are unclear. The aim of this Review is to summarise the clinical evidence for the dietary management of IBS; to discuss the challenges, burdens, and risks of dietary management; and to propose how these challenges, burdens, and risks should be mitigated and minimised in clinical practice., Competing Interests: Declaration of interests KW has received research grants related to diet and gut health and disease from the Almond Board of California, Danone, and the International Nut and Dried Fruit Council, and has received speaker fees from Danone and Yakult. KW is the holder of a joint patent to use volatile organic compounds as biomarkers in IBS (PCT/GB2020/051604) for which there is currently no product on the market. In the event of commercialisation into a product, the institution and inventor KW would receive royalties. KW receives royalties from Wiley Publishing in relation to an academic textbook on nutrition and dietetics in gastroenterology. HB-M is supported by a grant from the National Institute of Diabetes and Digestive and Kidney Diseases (K23 DK131334). HMS is supported by a National Health and Medical Research Council Emerging Leadership Award (APP2018118), and has received a research grant from the Rome Foundation (paid to institution). HMS is on the editorial advisory board for The Lancet Gastroenterology & Hepatology. ACF declares no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Context: Dietary fibers hold potential to influence depressive and anxiety outcomes by modulating the microbiota-gut-brain axis, which is increasingly recognized as an underlying factor in mental health maintenance., Objective: Evidence for the effects of fibers on depressive and anxiety outcomes remains unclear. To this end, a systematic literature review and a meta-analysis were conducted that included observational studies and randomized controlled trials (RCTs)., Data Sources: The PubMed, Embase, CENTRAL, CINAHL, and PsychINFO databases were searched for eligible studies., Data Extraction: Study screening and risk-of-bias assessment were conducted by 2 independent reviewers., Data Analysis: Meta-analyses via random effects models were performed to examine the (1) association between fiber intake and depressive and anxiety outcomes in observational studies, and (2) effect of fiber intervention on depressive and anxiety outcomes compared with placebo in RCTs. A total of 181 405 participants were included in 23 observational studies. In cross-sectional studies, an inverse association was observed between fiber intake and depressive (Cohen's d effect size [d]: -0.11; 95% confidence interval [CI]: -0.16, -0.05) and anxiety (d = -0.25; 95%CI, -0.38, -0.12) outcomes. In longitudinal studies, there was an inverse association between fiber intake and depressive outcomes (d = -0.07; 95%CI, -0.11, -0.04). In total, 740 participants were included in 10 RCTs, all of whom used fiber supplements. Of note, only 1 RCT included individuals with a clinical diagnosis of depression. No difference was found between fiber supplementation and placebo for depressive (d = -0.47; 95%CI, -1.26, 0.31) or anxiety (d = -0.30; 95%CI, -0.67, 0.07) outcomes., Conclusion: Although observational data suggest a potential benefit for higher fiber intake for depressive and anxiety outcomes, evidence from current RCTs does not support fiber supplementation for improving depressive or anxiety outcomes. More research, including RCTs in clinical populations and using a broad range of fibers, is needed., Systematic Review Registration: PROSPERO registration no. CRD42021274898., (© The Author(s) 2023. Published by Oxford University Press on behalf of the International Life Sciences Institute.)

Diet is a major determinant of the gastrointestinal microbiome composition and function, yet our understanding of how it impacts the efficacy of prebiotics and probiotics is limited. Here we examine current evidence of dietary influence on prebiotic and probiotic efficacy in human studies, including potential mechanisms. We propose that habitual diet be included as a variable in prebiotic and probiotic intervention studies. This recommendation is based on the potential mechanisms via which diet can affect study outcomes, either directly or through the gut microbiome. We consider the challenges and opportunities of dietary assessment in this context. Lastly, we provide recommendations for the design, conduct and reporting of human clinical trials of prebiotics and probiotics (and other biotic interventions) to account for any effect of diet and nutrition., (© 2024. Springer Nature Limited.)

Double-blind, placebo-controlled, randomized controlled trials are the gold standard for clinical trials in nutrition science. For trials of whole diets, dietary counseling is advantageous as they offer clinical translatability although can vary in the fidelity of the intended intervention from participant to participant and across studies. Feeding trials, in which most or all food is provided, offer high precision and can provide proof-of-concept evidence that a dietary intervention is efficacious and can also better evaluate the effect of known quantities of foods and nutrients on physiology. However, they come with additional methodological complexities. Feeding trials also call for a variety of unique methodological considerations, not least of which relate to the design and delivery of diets to participants. This review aims to provide a comprehensive summary of recommendations for design and conduct of feeding trials, encompassing domiciled and nondomiciled feeding trials. Several pertinent aspects of trial design and methodology are discussed, including defining the study population to maximize retention, safety, and generalizability of findings, recommendations for design of control interventions and optimizing blinding, and specific considerations for clinical populations. A detailed stepwise process for menu design, development, validation, and delivery are also presented. These recommendations aim to facilitate methodologic consistency and execution of high-quality feeding trials, ultimately facilitating improved understanding of the role of diet in treating disease and the underpinning mechanisms., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Nutritional epidemiological studies have evolved from a focus of single nutrients to diet patterns to capture the protective role of healthy diets on chronic disease development. Similarly, in inflammatory bowel disease (IBD), a healthy diet may be protective against its development in individuals with genetic susceptibility, but the definitions of the optimal diet pattern deserve further exploration. Hence, this review article presents evidence, mainly from prospective cohort studies, for the role of diet quality based on adherence to dietary guidelines, traditional and modern diet patterns in the prevention of IBD. Findings from a limited number of studies on diet quality suggest that high diet quality scores are associated with lower risk of developing Crohn's disease, but the data are inconsistent for ulcerative colitis (UC). There are signals that a Mediterranean diet pattern reduces the risk of Crohn's disease but, again, the data are inconsistent and further studies are much needed. Finally, the evidence is conflicting regarding the role of food additives, with difficulties in the assessment of their intake, namely non-nutritive sweeteners and emulsifiers, precluding accurate assessment of a relationship with IBD risk. In contrast, emerging evidence for a role of ultra-processed food in the development of Crohn's disease but not UC is identified. Given the potential influence of diet quality, a Mediterranean diet and ultra-processed food intake on the risk of Crohn's disease, assessment and implementation of dietary advice for these patients need to be tailored. The search for an optimal diet for UC remains elusive and further research for increasing the evidence in the area is greatly needed., (© 2024 The Author(s). JGH Open published by Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.)

Background: Diet and exercise are important components of treatment for complex chronic conditions, however access to allied health support is limited. When available, support is often siloed and fragmented. Digital health incorporating patient choice may help to align health care services with preferences and goals. This study evaluated the implementation of a ubiquitously accessible patient-centred digital health diet and exercise service., Methods: U-DECIDE was a single-centre, 26-week randomised controlled trial set in kidney and liver disease clinics in a tertiary hospital in Brisbane, Australia. Participants were adults with a complex chronic condition referred for dietetic consultation with at least one feature of the metabolic syndrome. All participants received a dietary consultation, an activity monitor and usual care. Intervention participants were offered one text message per week and access to additional digital health options (increased text message frequency, nutrition app, exercise app, group-based diet and/or exercise video consultations). The primary outcome of feasibility was determined by safety (study-related serious adverse events: SRSAEs), recruitment (≥ 50% eligible patients), retention (≥ 70%), exposure uptake (≥ 75% of intervention group had greater access to health professional contact than comparator) and video consultation adherence (≥ 80% attendance). Secondary outcomes included process evaluation metrics and clinical outcomes., Results: Of 67 participants (intervention n = 33, comparator n = 34), 37 (55%) were men, median (IQR) age was 51 (41-58) years. The most chosen digital health options were the nutrition app (n = 29, 88%) and exercise video consultations (n = 26, 79%). Only one participant chose no additional digital health options. The intervention group had no SRSAEs. The study exceeded targets for recruitment (52%), retention (81%) and exposure uptake (94%). Video consultation adherence was 42%. Engagement across digital health options was inconsistent., Conclusions: Digital health options incorporating patient choice were feasible and can be offered to people with complex chronic disease as a service model option., Trial Registration: Australia and New Zealand Trials Register: Trial Registration Number: ACTRN12620001282976. Registered 27th November 2020., (© 2024. The Author(s).)

Postprandial, or meal-related, symptoms, such as abdominal pain, early satiation, fullness or bloating, are often reported by patients with disorders of gut-brain interaction, including functional dyspepsia (FD) or irritable bowel syndrome (IBS). We propose that postprandial symptoms arise via a distinct pathophysiological process. A physiological or psychological insult, for example, acute enteric infection, leads to loss of tolerance to a previously tolerated oral food antigen. This enables interaction of both the microbiota and the food antigen itself with the immune system, causing a localised immunological response, with activation of eosinophils and mast cells, and release of inflammatory mediators, including histamine and cytokines. These have more widespread systemic effects, including triggering nociceptive nerves and altering mood. Dietary interventions, including a diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols, elimination of potential food antigens or gluten, IgG food sensitivity diets or salicylate restriction may benefit some patients with IBS or FD. This could be because the restriction of these foods or dietary components modulates this pathophysiological process. Similarly, drugs including proton pump inhibitors, histamine-receptor antagonists, mast cell stabilisers or even tricyclic or tetracyclic antidepressants, which have anti-histaminergic actions, all of which are potential treatments for FD and IBS, act on one or more of these mechanisms. It seems unlikely that food antigens driving intestinal immune activation are the entire explanation for postprandial symptoms in FD and IBS. In others, fermentation of intestinal carbohydrates, with gas release altering reflex responses, adverse reactions to food chemicals, central mechanisms or nocebo effects may dominate. However, if the concept that postprandial symptoms arise from food antigens driving an immune response in the gastrointestinal tract in a subset of patients is correct, it is paradigm-shifting, because if the choice of treatment were based on one or more of these therapeutic targets, patient outcomes may be improved., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Diet is fundamental to the care of irritable bowel syndrome (IBS). However, some approaches are not appropriate for individuals experiencing psychological symptoms., Aims: To assess feasibility of a Mediterranean diet in IBS and its impact on gastrointestinal and psychological symptoms., Methods: We recruited adults with Rome IV IBS and mild or moderate anxiety and/or depressive symptoms to an unblinded 6-week randomised controlled trial. Patients were randomised to Mediterranean diet counselling or habitual diet. We collected gastrointestinal and psychological symptom data, dietary data and stool samples for metagenomic sequencing., Results: We randomised 59 individuals (29 Mediterranean diet, 30 control); 48 completed the study. The Mediterranean Diet Adherence Screener score was higher in the Mediterranean diet group than controls at week 6 (7.5 [95% CI: 6.9-8.0] vs. 5.7 [5.2-6.3], p < 0.001), and there was a greater score increase than controls (2.1 [95% CI: 1.3-2.9] vs. 0.5 [95% CI: 0.1-1.0], p = 0.004), demonstrating Mediterranean diet feasibility. There was a greater proportion of gastrointestinal symptom responders in the Mediterranean diet group than controls (24/29, 83% vs. 11/30, 37%, p < 0.001) and depression responders (15/29, 52% vs. 6/30 20%, p = 0.015). There was no difference in FODMAP intake at week 6 (p = 0.51). Gastrointestinal adverse events were similar (p = 0.588). There were no differences in change in microbiome parameters between groups., Conclusions: A Mediterranean diet is feasible in IBS and leads to improvement in gastrointestinal and psychological symptoms. Although this study was unblinded, these findings together with the broader benefits of the Mediterranean diet, provide strong impetus for future research in IBS. Australia New Zealand Clinical Trials Registry: ACTRN12620001362987., (© 2023 The Authors. Alimentary Pharmacology & Therapeutics published by John Wiley & Sons Ltd.)

Purpose: Modifying gut bacteria in children with autism may influence behaviour, with potential to improve family functioning. We conducted a randomised controlled trial to assess the effect of prebiotics on behaviour, gastrointestinal symptoms and downstream effects on parental quality of life., Method: Children with autism (4-10yrs) were randomised to 2.4 g/d of prebiotic (GOS) or placebo for six weeks. Pre and post stools samples were collected, and validated questionnaires used to measure change in social and mealtime behaviours, GI symptoms and pQOL. Linear mixed models evaluated group differences for behavioural variables, and Mann Whitney U tests were used to compare change between-groups for GI symptoms, differential abundance of genera and alpha diversity of the microbiome., Results: Thirty-three parent-child dyads completed the trial. No group difference was seen for behavioural variables but both groups improved significantly from baseline. There was a medium effect size between groups for GI symptoms (d = 0.47) and pQOL (d = 0.44) driven by greater improvements in the prebiotic group. Bifidobacterium increased threefold following prebiotics (1.4-5.9%, p < 0.001) with no change in controls. Supplements were well tolerated, compliance with dose 94%., Conclusion: Prebiotics modify levels of Bifidobacterium and prove well tolerated but in this instance, resulted in only marginal effects on GI symptoms and pQOL. A larger sample of children with more severe symptoms could help to determine the potential of prebiotics in autism., Trial Registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12619000615189 ., (© 2024. The Author(s).)

Objective: The gut microbiota is implicated in several symptoms and biological pathways relevant to anorexia nervosa (AN). Investigations into the role of the gut microbiota in AN are growing, with a specific interest in the changes that occur in response to treatment. Findings suggest that microbial species may be associated with some of the symptoms common in AN, such as depression and gastrointestinal disturbances (GID). Therefore, researchers believe the gut microbiota may have therapeutic relevance. Whilst research in this field is rapidly expanding, the unique considerations relevant to conducting gut microbiota research in individuals with AN must be addressed., Method: We provide an overview of the published literature investigating the relationship between the gut microbiota and symptoms and behaviors present in AN, discuss important challenges in gut microbiota research, and offer recommendations for addressing these. We conclude by summarizing research design priorities for the field to move forward., Results: Several ways exist to reduce participant burden and accommodate challenges when researching the gut microbiota in individuals with AN., Discussion: Recommendations from this article are foreseen to encourage scientific rigor and thoughtful protocol planning for microbiota research in AN, including ways to reduce participant burden. Employing such methods will contribute to a better understanding of the role of the gut microbiota in AN pathophysiology and treatment., Public Significance: The field of gut microbiota research is rapidly expanding, including the role of the gut microbiota in anorexia nervosa. Thoughtful planning of future research will ensure appropriate data collection for meaningful interpretation while providing a positive experience for the participant. We present current challenges, recommendations for research design and priorities to facilitate the advancement of research in this field., (© 2023 The Authors. International Journal of Eating Disorders published by Wiley Periodicals LLC.)

Irritable bowel syndrome (IBS) affects 5-10% of the global population. Up to one-third of people with IBS also experience anxiety or depression. Gastrointestinal and psychological symptoms both drive health-care use in people with IBS, but psychological comorbidity seems to be more important for long-term quality of life. An integrated care approach that addresses gastrointestinal symptoms with nutrition and brain-gut behaviour therapies is considered the gold standard. However, best practice for the treatment of individuals with IBS who have a comorbid psychological condition is unclear. Given the rising prevalence of mental health disorders, discussion of the challenges of implementing therapy for people with IBS and anxiety and depression is critical. In this Review, we draw upon our expertise in gastroenterology, nutrition science and psychology to highlight common challenges that arise when managing patients with IBS and co-occurring anxiety and depression, and provide recommendations for tailoring clinical assessment and treatment. We provide best practice recommendations, including dietary and behavioural interventions that could be applied by non-specialists and clinicians working outside an integrated care model., (© 2023. Springer Nature Limited.)

Background: A low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet is increasingly used to manage symptoms in irritable bowel syndrome (IBS). Although this approach may alter the colonic microbiome, the nature of these changes has not been comprehensively synthesized., Objectives: The aim of this study was to conduct a systematic review with meta-analysis of randomized controlled trials examining the impact of a low FODMAP diet on the composition and function of the microbiome in patients with IBS., Methods: A systematic search was conducted for randomized controlled trials evaluating the effects of a low FODMAP diet on the colonic microbiome in patients with IBS in MEDLINE, EMBASE, CENTRAL, and Web of Science from inception to April 2022. Outcomes included diversity of the microbiome, specific bacterial abundances, fecal SCFA concentration, and fecal pH. For fecal SCFA concentrations and pH, meta-analyses were performed via a random-effects model., Results: Nine trials involving 403 patients were included. There were no clear effects of the low FODMAP diet on diversity of the microbiome. A low FODMAP diet consistently led to lower abundance of Bifidobacteria, but there were no clear effects on diversity of the microbiome or abundances of other specific taxa. There were no differences in total fecal SCFA concentration between the low FODMAP diet and control diets (standardized mean difference: -0.25; 95% CI: -0.63, 0.13; P = 0.20), nor were there differences for fecal concentrations of specific SCFAs or fecal pH., Conclusions: In patients with IBS, the effects of a low FODMAP diet on the colonic microbiome appear to be specific to Bifidobacteria with no consistent impacts on other microbiome metrics, including diversity, fecal SCFA concentrations, and fecal pH. Further, adequately powered trials are needed to confirm these findings.This review was registered at https://www.crd.york.ac.uk/prospero/ as CRD42020192243., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society for Nutrition.)

Despite advances in treatment of anorexia nervosa (AN), current therapeutic approaches do not fully consider gastrointestinal disturbances (GID), often present in AN. Addressing GID, both symptoms and disorders, is likely to improve treatment adherence and outcomes in people with AN. GID are complex and are linked to a range of factors related to eating disorder symptomology and can be impacted by nutritional treatment. It is not known which dietetic practices are currently used to address GID in AN. Therefore, this survey aimed to explore the perceived knowledge, attitudes, and practices (KAP) of Australian dietitians treating AN and co-occurring GID. Seventy dietitians participated by completing an online survey. Knowledge scores were calculated based on correct responses to knowledge items (total: 12 points); and two groups were generated: higher knowledge (≥10 points, n = 31) and lower knowledge (≤9 points, n = 39). A greater proportion of dietitians with higher knowledge recognized the role of GID in pathogenesis of AN ( p = 0.002) and its impact on quality of life ( p = 0.013) and screened for GID ( p ≤ 0.001), compared with those with lower knowledge. These results suggest that attitudes and practices toward patients presenting with AN and GID differ depending on level of knowledge. This may have important implications for treatment outcomes for individuals with AN and GID.

Background: The metabolic syndrome is common across many complex chronic disease groups. Advances in health technology have provided opportunities to support lifestyle interventions., Objective: The purpose of this study is to test the feasibility of a health technology-assisted lifestyle intervention in a patient-led model of care., Methods: The study is a single-center, 26-week, randomized controlled trial. The setting is specialist kidney and liver disease clinics at a large Australian tertiary hospital. The participants will be adults with a complex chronic condition who are referred for dietetic assessment and display at least one feature of the metabolic syndrome. All participants will receive an individualized assessment and advice on diet quality from a dietitian, a wearable activity monitor, and standard care. Participants randomized to the intervention group will receive access to a suite of health technologies from which to choose, including common base components (text messages) and optional components (online and mobile app-based nutrition information, an online home exercise program, and group-based videoconferencing). Exposure to the optional aspects of the intervention will be patient-led, with participants choosing their preferred level of engagement. The primary outcome will be the feasibility of delivering the program, determined by safety, recruitment rate, retention, exposure uptake, and telehealth adherence. Secondary outcomes will be clinical effectiveness, patient-led goal attainment, treatment fidelity, exposure demand, and participant perceptions. Primary outcome data will be assessed descriptively and secondary outcomes will be assessed using an analysis of covariance. This study will provide evidence on the feasibility of the intervention in a tertiary setting for patients with complex chronic disease exhibiting features of the metabolic syndrome., Results: The study was funded in 2019. Enrollment has commenced and is expected to be completed by June 2022. Data collection and follow up are expected to be completed by December 2022. Results from the analyses based on primary outcomes are expected to be submitted for publication by June 2023., Conclusions: The study will test the implementation of a health technology-assisted lifestyle intervention in a tertiary outpatient setting for a diverse group of patients with complex chronic conditions. It is novel in that it embeds patient choice into intervention exposure and will inform health service decision-makers in regards to the feasibility of scale and spread of technology-assisted access to care for a broader reach of specialist services., Trial Registration: Australian New Zealand Clinical Trial Registry ACTRN12620001282976; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=378337., International Registered Report Identifier (irrid): DERR1-10.2196/37556., (©Riley C C Brown, Dev K Jegatheesan, Marguerite M Conley, Hannah L Mayr, Jaimon T Kelly, Lindsey Webb, Amandine Barnett, Heidi M Staudacher, Nicola W Burton, Nicole M Isbel, Graeme A Macdonald, Katrina L Campbell, Jeff S Coombes, Shelley E Keating, Ingrid J Hickman. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 28.07.2022.)

Objective: A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) is recommended for irritable bowel syndrome (IBS), if general lifestyle and dietary advice fails. However, although the impact of a low FODMAP diet on individual IBS symptoms has been examined in some randomised controlled trials (RCTs), there has been no recent systematic assessment, and individual trials have studied numerous alternative or control interventions, meaning the best comparator is unclear. We performed a network meta-analysis addressing these uncertainties., Design: We searched the medical literature through to 2 April 2021 to identify RCTs of a low FODMAP diet in IBS. Efficacy was judged using dichotomous assessment of improvement in global IBS symptoms or improvement in individual IBS symptoms, including abdominal pain, abdominal bloating or distension, and bowel habit. Data were pooled using a random effects model, with efficacy reported as pooled relative risks (RRs) with 95% CIs, and interventions ranked according to their P-score., Results: We identified 13 eligible RCTs (944 patients). Based on failure to achieve an improvement in global IBS symptoms, a low FODMAP diet ranked first vs habitual diet (RR of symptoms not improving=0.67; 95% CI 0.48 to 0.91, P-score=0.99), and was superior to all other interventions. Low FODMAP diet ranked first for abdominal pain severity, abdominal bloating or distension severity and bowel habit, although for the latter it was not superior to any other intervention. A low FODMAP diet was superior to British Dietetic Association (BDA)/National Institute for Health and Care Excellence (NICE) dietary advice for abdominal bloating or distension (RR=0.72; 95% CI 0.55 to 0.94). BDA/NICE dietary advice was not superior to any other intervention in any analysis., Conclusion: In a network analysis, low FODMAP diet ranked first for all endpoints studied. However, most trials were based in secondary or tertiary care and did not study effects of FODMAP reintroduction and personalisation on symptoms., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

There is accumulating evidence for the fundamental role of diet in the integrated care of disorders of gut-brain interaction. Food is a complex mixture of components with individual, synergistic, and antagonistic effects, compared with the relative purity of a pharmaceutical. Food is also an inherent part of individuals' daily lives, and food choice is strongly tied to food preferences, personal beliefs, cultural and religious practices, and economic status, which can influence its ability to function as a therapeutic intervention. Hence, randomized controlled trials of dietary interventions carry unique methodological complexities that are not applicable to pharmaceutical trials that if disregarded can pose significant risk to trial quality. The challenges of designing and delivering the dietary intervention depend on the type of intervention (i.e., nutrient vs food supplementation or whole-diet intervention). Furthermore, there are multiple modes of delivery of dietary interventions, each with their own advantages (e.g., the high precision of feeding trials and the strong clinical applicability of dietary counseling trials). Randomized placebo-controlled trials of dietary interventions are possible with sufficient attention to their design and methodological nuances. Collaboration with experts in nutrition and dietetics is essential for the planning phase; however, even with expert input, not all challenges can be overcome. Researchers undertaking future dietary trials must be transparent in reporting these challenges and approaches for overcoming them. This review aims to provide guiding principles and recommendations for addressing these challenges to facilitate the conduct and reporting of high-quality trials that inform and improve clinical practice., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The American College of Gastroenterology.)

Background: Short-term trials demonstrate the low FODMAP diet improves symptoms of irritable bowel syndrome (IBS) but impacts nutrient intake and the gastrointestinal microbiota. The aim of this study was to investigate clinical symptoms, nutrient intake, and microbiota of patients with IBS 12 months after starting a low FODMAP diet., Methods: Participants enrolled in a previous short-term clinical trial and who had been through structured FODMAP restriction, reintroduction, and personalization were invited to participate in a follow-up study at one time point at 12 months. Gastrointestinal symptoms, stool output, dietary intake, and quality of life were recorded. Stool samples were collected and analyzed for microbiota (qPCR) and short-chain fatty acids (SCFA). Data were compared with baseline (prior to any intervention in the original clinical trial) using non-parametric statistics., Key Results: Eighteen participants were included in the study. Adequate relief of symptoms occurred in 5/18 (28%) at baseline and increased to 12/18 (67%) following long-term personalized low FODMAP diet (p = 0.039). There was a reduction in IBS-SSS total score between baseline (median 227, IQR 99) and long term (154, 89; p < 0.001). Bifidobacteria abundance was not different between baseline (median 9.29 log10 rRNA genes/g, IQR 1.45) and long term (9.20 log10 rRNA genes/g, 1.41; p = 0.766, q = 0.906); however, there were lower concentrations of total SCFA, acetate, propionate, and butyrate., Conclusions: In this long-term analysis, two thirds of patients reported adequate relief of symptoms after 12 months of personalized low FODMAP diet that did not result in differences from baseline in Bifidobacteria. FODMAP reintroduction and personalization may normalize some of the effects of short-term FODMAP restriction., (© 2021 John Wiley & Sons Ltd.)

Background: Certain dietary constituents may provoke symptoms of functional dyspepsia (FD); however, there is an absence of dietary trials testing specific dietary interventions. Empirically derived dietary strategies and the low FODMAP diet are frequently used in practice. This study aimed to compare the effectiveness of low FODMAP dietary advice with standard dietary advice for reducing epigastric and overall gastrointestinal symptoms in individuals with FD., Methods: Data were collected from 59 consecutive eligible individuals with FD attending an initial and review outpatient dietetic consultation at Princess Alexandra Hospital. Of these, 40 received low FODMAP advice and 19 received standard dietary advice. As part of usual care, the Structured Assessment of Gastrointestinal Symptom Scale (SAGIS) was used to assess epigastric (maximum score = 28) and overall gastrointestinal symptoms (maximum score = 88). Dietary adherence data were collected, and change in symptom score and proportion of responders (defined as a ≥30% reduction in score) for epigastric and total symptoms was calculated., Key Results: Most individuals (48/59, 81%) had FD and coexisting irritable bowel syndrome. There was a greater reduction in epigastric score in those receiving low FODMAP dietary advice compared with those receiving standard advice (est. marginal mean [95% CI]: -3.6 [-4.9, -2.2] vs. -0.9 [-2.9, 1.1], p = 0.032) and total symptom score (-9.4 [-12.4, -6.4] vs. -3.3 [-7.7, 1.1] p = 0.026). A greater proportion receiving low FODMAP dietary advice were responders versus those receiving standard advice (50% vs. 16%, p = 0.012). Dietary adherence did not differ between groups (p = 0.497)., Conclusions & Inferences: The low FODMAP diet appears more effective for improving epigastric symptoms in people with FD compared with standard advice. A randomized controlled trial is required to substantiate these findings., (© 2021 John Wiley & Sons Ltd.)

Diet is one of the strongest modulators of the gut microbiome. However, the complexity of the interactions between diet and the microbial community emphasises the need for a robust study design and continued methodological development. This review aims to summarise considerations for conducting high-quality diet-microbiome research, outline key challenges unique to the field, and provide advice for addressing these in a practical manner useful to dietitians, microbiologists, gastroenterologists and other diet-microbiome researchers. Searches of databases and references from relevant articles were conducted using the primary search terms 'diet', 'diet intervention', 'dietary analysis', 'microbiome' and 'microbiota', alone or in combination. Publications were considered relevant if they addressed methods for diet and/or microbiome research, or were a human study relevant to diet-microbiome interactions. Best-practice design in diet-microbiome research requires appropriate consideration of the study population and careful choice of trial design and data collection methodology. Ongoing challenges include the collection of dietary data that accurately reflects intake at a timescale relevant to microbial community structure and metabolism, measurement of nutrients in foods pertinent to microbes, improving ability to measure and understand microbial metabolic and functional properties, adequately powering studies, and the considered analysis of multivariate compositional datasets. Collaboration across the disciplines of nutrition science and microbiology is crucial for high-quality diet-microbiome research. Improvements in our understanding of the interaction between nutrient intake and microbial metabolism, as well as continued methodological innovation, will facilitate development of effective evidence-based personalised dietary treatments., (© 2021 The British Dietetic Association Ltd.)

Objective: Gastrointestinal (GI) disturbances are a frequent and burdensome experience for patients with anorexia nervosa (AN). How GI symptoms respond to current interventions is not well characterized, yet is critical to facilitate treatment success, and to inform the development of new treatments for AN. Therefore, the aim of this systematic review was to identify which treatments are effective in improving GI symptoms in patients with AN., Method: A systematic search for studies of AN treatments measuring GI symptoms pre- and post-treatment was conducted in May 2020 (PROSPERO ID: CRD42020181328). After removal of duplicates, title and abstracts of 3,370 studies were screened. Methodological quality was assessed using National Institute of Health Quality Assessment Tool., Results: Following full-text screening, 13 studies (12 observational studies and 1 randomized double-blind placebo-controlled trial) with 401 participants met eligibility criteria and were included. All observational studies included a component of nutritional rehabilitation, with half (n = 6) involving concurrent psychological treatment. The randomized controlled trial reported a drug therapy. Eleven studies reported an improvement in all (n = 6) or at least one (n = 5) patient-reported GI symptom following treatment. Two studies reported no change. Methodological quality was fair or poor across all studies., Discussion: This is the first systematic review to synthesize available evidence on the trajectory of patient-reported GI symptoms from commencement to end of treatment for AN. The results suggest that most studies showed improvement in one or more GI symptom in response to current treatments. Future therapeutic approaches should consider GI symptoms within their design for optimal treatment adherence and outcomes., (© 2021 Wiley Periodicals LLC.)

The frequent co-occurrence of irritable bowel syndrome and the common mental disorders of anxiety and depression is well established. A range of biological and psychosocial disease mechanisms are common to both disorders, many of which contribute to a dysregulated gut-brain axis. Clinical and subthreshold psychological comorbidity adds to the functional impairment and disease burden in individuals with irritable bowel syndrome. Progress is being made with regard to understanding irritable bowel syndrome in the clinical setting from a biopsychosocial perspective. However, until now, most trials of irritable bowel syndrome treatment still consider the disease as a gut disorder in isolation, which leaves major gaps in knowledge about disease-disease interactions and treatment outcomes in irritable bowel syndrome. In this Viewpoint, we review the epidemiology, pathophysiology, and management of anxiety and depression in individuals with irritable bowel syndrome. We also provide methodological recommendations for future randomised controlled trials and outline guidance for research that better incorporates psychiatric comorbidity into its design, with a view to improve treatment outcomes for individuals with irritable bowel syndrome., (Crown Copyright © 2021 Published by Elsevier Ltd. All rights reserved.)

Background and Aims: Diet is both a modulator of the gastrointestinal microbiota and an important therapy in irritable bowel syndrome (IBS). We aimed to comprehensively (i) identify diet-microbiota associations in adults with IBS consuming habitual diet; (ii) assess the impact of two nutritional interventions on the microbiota; and (iii) determine whether baseline microbiota can predict clinical response to diet or probiotic intervention., Methods: Data were analyzed from 95 individuals with IBS participating in a previously published 4-week 2x2 factorial design randomized controlled trial investigating the impact of the low FODMAP diet (LFD) and co-administration of a probiotic. Diet was assessed at four hierarchical levels and partial 16S rRNA gene sequencing was used to profile the microbiota., Results: There were numerous diet-microbiota associations especially at the nutrient level, including a negative association between protein and Bifidobacterium abundance (r s  = -0.358, p < 0.001). After correction for multiple testing, the significance for this association (q = 0.237) and all others was lost. Low FODMAP diet led to changes in abundance of major saccharolytic genera compared with sham diet, including higher Bacteroides (LFD 34.1% (15.7%) vs sham 23.3% (15.2%), q = 0.01) and lower Bifidobacterium (0.9% (1.0%) vs 2.1%, (2.5%) q = 0.029). Compared with placebo, probiotic supplementation led to higher Lactobacillus (probiotic 0.08% (0.1%) vs placebo 0.03% (0.2%), q < 0.001), and Streptococcus abundance (2.0% (2.2%) vs 0.6% (1.2%), q = 0.001). The probiotic treatment buffered the impact of the low FODMAP diet on Bifidobacterium. Baseline microbiota did not predict clinical response to either intervention., Conclusions: Although diet modifies the gut microbiota, bivariate correlation analysis may only provide a limited explanation of the complex diet interactions with individual gut bacteria in IBS. Some diet interventions modify the microbiota in IBS., Trial Registry: ISRCTN (http://www.isrctn.com) Registered under ISRCTN registry identifier no.ISRCTN02275221., Competing Interests: Conflict of Interest ML and KW are co-inventors of a mobile application relating to the low FODMAP diet. KW has acted as a consultant for Danone, and received research funding from Danone. FR receives consultation fees from Lavida Food Co. that distributes low FODMAP food products in the UK. All other authors have no other relevant conflicts of interest to declare., (Copyright © 2020 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

Background: Online interventions can be a cost-effective and efficient way to deliver programs to large numbers of people regardless of geographic location. However, attrition in web-based interventions is often an issue. Developing ways to keep participants engaged is important for ensuring validity and limiting potential biases. We developed a web-based dietary intervention as part of The My Food & Mood study which aimed to optimize ways to engage participants with low mood or depressive symptoms to promote dietary behavior change. Different versions of the My Food & Mood program were tested during optimization. Iterations were developed based on user feedback and usage analysis., Objective: The purpose of this study was to compare engagement and nonusage attrition across 4 program iterations-which differed by platform format, delivery mode, and activity type-to create an optimized version., Methods: Each program version contained modular videos with key activities with respect to implementing behavior change techniques of equivalent levels of required participation and length: version 1.0, desktop program and smartphone app; version 2.1, desktop or smartphone program; version 2.2, desktop program; and version 3.0, smartphone app. Adults with PHQ-8 scores of 5 or greater were recruited online and assigned to 1 of the 4 versions. Participants were asked to use the program for 8 weeks and complete measures at weeks 4 and 8. Engagement data were collected from the web-based platform system logs and customized reports. Cox regression survival analysis examined nonusage attrition and Kruskal-Wallis tests compared engagement across each cohort., Results: A total of 614 adults participated. Kruskal-Wallis tests showed significant differences across the 4 cohorts in all engagement measures. The smartphone app (version 3.0) had the greatest engagement as measured by weeks engaged, total usage time, total time key activities, number of active sessions, percentage of activities completed against protocol, goals completed, and percentage of videos watched. Cox regression multivariate survival analysis showed referral from a health practitioner (hazard ratio [HR] 0.344, P=.001) and greater proficiency with computers (HR 0.796, P=.049) reduced the risk of nonusage attrition. Computer confidence was associated with an increased risk of nonusage attrition., Conclusions: My Food & Mood version 3.0, a dietary intervention delivered via smartphone app with self-monitoring tools for diet quality and mood monitoring, was the version with greatest engagement in a population with low mood or depression. The iterative design techniques employed and analysis of feedback from participants resulted in a program that achieved lower rates of nonusage attrition and higher rates of intensity of use., (©Claire Louise Young, Mohammadreza Mohebbi, Heidi M Staudacher, Frances Kay-Lambkin, Michael Berk, Felice Nellie Jacka, Adrienne O'Neil. Originally published in JMIR Mental Health (http://mental.jmir.org), 31.03.2021.)

Rapid excess weight gain and metabolic complications contribute to poor outcomes following liver transplant care. Providing specialist lifestyle intervention with equitable access is a challenge for posttransplant service delivery., Methods: This study investigated the feasibility of a 12-wk telehealth delivered lifestyle intervention for liver transplant recipients (randomized controlled trial with a delayed intervention control group). The intervention included 14 group sessions facilitated by nutrition and exercise specialists via video streaming telehealth and participants used their own devices. Feasibility was assessed across session attendance, the adequacy, acceptability, and confidence with the telehealth technology and adherence to diet (Mediterranean Diet Adherence Score). Secondary pooled analysis of effectiveness was determined from changes in quality of life and metabolic syndrome severity score., Results: Of the 35 participants randomized, dropout was 22.8% (n = 8) and overall session attendance rate was 60%. Confidence with and adequacy of home technology was rated high in 96% and 91% of sessions, respectively. Participants randomized to the intervention significantly improved Mediterranean Diet Adherence Score (2-point increase [95% confidence interval, 1.5-3.4] versus control 0 point change [95% confidence interval, -1.4 to 1.2]; P  = 0.004). Intervention (within group) analysis found the intervention significantly decreased the metabolic syndrome severity score (-0.4 [95% confidence interval, -0.6 to -0.1] P  = 0.01), and improved mental health-related quality of life (2.5 [95% confidence interval, 0.4-4.6] P  = 0.03)., Conclusions: A cardioprotective lifestyle intervention delivered via telehealth is feasible for liver transplant recipients and may improve access to specialist care to support metabolic health and wellness after transplant., Competing Interests: The authors disclose no conflict of interest, (Copyright © 2021 The Author(s). Transplantation Direct. Published by Wolters Kluwer Health, Inc.)

There is accumulating evidence from observational and intervention studies in nutritional psychiatry regarding the importance of diet for mental health outcomes across the lifespan. Here, we synthesise this evidence, including findings from large meta-analyses showing cross-sectional and prospective associations between diet quality and mental health, even following adjustment for relevant confounding factors. Potential mechanistic pathways underpinning these associations include those of the gut-brain axis, demonstrated mostly in animal models. Dietary fibre is an important component of healthy diet and may be relevant for common mental disorders, with some studies showing a dose-dependent relationship between fibre intake and risk of depression. The potential contribution of nutraceuticals is also discussed, such as omega-3 fatty acids, vitamins, minerals, and psychobiotics. We consider the relevance of special diets such as the ketogenic diet and food sensitivities in the management of severe mental illness (e.g., anorexia nervosa) and brain disease (e.g., Alzheimer's disease). Given the relatively early nature of research in nutritional psychiatry, there remain a number of challenges to its translation into clinical practice. These span individual, clinical, and societal domains. We conclude with a discussion of micro- and macroeconomic factors which may be considered in the successful application of nutritional psychiatry research to improve public health., (© 2021 S. Karger AG, Basel.)

The field of nutritional psychiatry has generated observational and efficacy data supporting a role for healthy dietary patterns in depression onset and symptom management. To guide future clinical trials and targeted dietary therapies, this review provides an overview of what is currently known regarding underlying mechanisms of action by which diet may influence mental and brain health. The mechanisms of action associating diet with health outcomes are complex, multifaceted, interacting, and not restricted to any one biological pathway. Numerous pathways were identified through which diet could plausibly affect mental health. These include modulation of pathways involved in inflammation, oxidative stress, epigenetics, mitochondrial dysfunction, the gut microbiota, tryptophan-kynurenine metabolism, the HPA axis, neurogenesis and BDNF, epigenetics, and obesity. However, the nascent nature of the nutritional psychiatry field to date means that the existing literature identified in this review is largely comprised of preclinical animal studies. To fully identify and elucidate complex mechanisms of action, intervention studies that assess markers related to these pathways within clinically diagnosed human populations are needed.

Background: Individuals with irritable bowel syndrome (IBS) may modify their diet, which may pose nutritional risk. Further, some dietary approaches, such as a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), are restrictive and may contribute to nutritional inadequacy., Objective: Our aim was to evaluate habitual nutrient intake, diet quality, and diversity in IBS and the effect of a 4-week low FODMAP diet on these parameters compared with controls., Design: Data from two randomized controlled trials were included for this secondary analysis. Participants were randomized to low FODMAP diet (n=63) or control diet (sham diet n=48, habitual diet n=19)., Participants/setting: Participants included 130 individuals with IBS referred to a tertiary center in London, UK between January 2010 to June 2011 and January 2013 to November 2014., Intervention: Participants in one trial were randomized to receive either low FODMAP dietary counseling or sham control dietary counseling. In the other, they were randomized to receive low FODMAP dietary counseling or to continue habitual diet. All advice was provided by a specialist dietitian., Main Outcome Measures: Habitual (usual) dietary intake at baseline (n=130) and after a 4-week intervention period was measured using 7-day food records., Statistical Analyses Performed: Analysis of covariance and χ 2 tests evaluated differences across groups at 4 weeks., Results: When examining habitual intake of individuals with IBS, fiber intake was low, with only 6 (5%) achieving the target (30 g/day). In those receiving low FODMAP advice, there was no difference in intake of most nutrients compared with controls. However, there was lower intake of starch (109 g/day) vs habitual control diet (128 g/day; P=0.030), and higher intake of vitamin B-12 (6.1 μg/day) vs habitual (3.9 μg/day) and sham control diets (4.7 μg/day; P<0.01). Overall scores for diet quality were lower after low FODMAP advice vs habitual control diet (P<0.01)., Conclusion: This study demonstrates many individuals with IBS fail to meet dietary reference values for multiple nutrients. A 4-week low FODMAP diet, when delivered by a specialist dietitian, does not impact on intake of most nutrients or diet diversity but decreases diet quality compared with control diets., (Copyright © 2020 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.)

Dietary intervention is a challenge in clinical practice because of inter-individual variability in clinical response. Gut microbiota is mechanistically relevant for a number of disease states and consequently has been incorporated as a key variable in personalised nutrition models within the research context. This paper aims to review the evidence related to the predictive capacity of baseline microbiota for clinical response to dietary intervention in two specific health conditions, namely, obesity and irritable bowel syndrome (IBS). Clinical trials and larger predictive modelling studies were identified and critically evaluated. The findings reveal inconsistent evidence to support baseline microbiota as an accurate predictor of weight loss or glycaemic response in obesity, or as a predictor of symptom improvement in irritable bowel syndrome, in dietary intervention trials. Despite advancement in quantification methodologies, research in this area remains challenging and larger scale studies are needed until personalised nutrition is realistically achievable and can be translated to clinical practice.

Background: Dysfunction of the gut microbiota is frequently reported as a manifestation of chronic diseases, and therefore presents as a modifiable risk factor in their development. Diet is a major regulator of the gut microbiota, and certain types of dietary fiber may modify bacterial numbers and metabolism, including short-chain fatty acid (SCFA) generation., Objective: A systematic review and meta-analysis were undertaken to assess the effect of dietary fiber interventions on gut microbiota composition in healthy adults., Design: A systematic search was conducted across MEDLINE, EMBASE, CENTRAL, and CINAHL for randomized controlled trials using culture and/or molecular microbiological techniques evaluating the effect of fiber intervention on gut microbiota composition in healthy adults. Meta-analyses via a random-effects model were performed on alpha diversity, prespecified bacterial abundances including Bifidobacterium and Lactobacillus spp., and fecal SCFA concentrations comparing dietary fiber interventions with placebo/low-fiber comparators., Results: A total of 64 studies involving 2099 participants were included. Dietary fiber intervention resulted in higher abundance of Bifidobacterium spp. (standardized mean difference (SMD): 0.64; 95% CI: 0.42, 0.86; P < 0.00001) and Lactobacillus spp. (SMD: 0.22; 0.03, 0.41; P = 0.02) as well as fecal butyrate concentration (SMD: 0.24; 0.00, 0.47; P = 0.05) compared with placebo/low-fiber comparators. Subgroup analysis revealed that fructans and galacto-oligosaccharides led to significantly greater abundance of both Bifidobacterium spp. and Lactobacillus spp. compared with comparators (P < 0.00001 and P = 0.002, respectively). No differences in effect were found between fiber intervention and comparators for α-diversity, abundances of other prespecified bacteria, or other SCFA concentrations., Conclusions: Dietary fiber intervention, particularly involving fructans and galacto-oligosaccharides, leads to higher fecal abundance of Bifidobacterium and Lactobacillus spp. but does not affect α-diversity. Further research is required to better understand the role of individual fiber types on the growth of microbes and the overall gut microbial community. This review was registered at PROSPERO as CRD42016053101.