Eating less meat is increasingly seen as a healthier, more ethical option. This is leading to growing numbers of flexitarian consumers looking for plant-based meat alternatives (PBMAs) to replace at least some of the animal meat they consume. Popular PBMA products amongst flexitarians, including plant-based mince, burgers, sausages and meatballs, are often perceived as low-quality, ultra-processed foods. However, we argue that the mere industrial processing of ingredients of plant origin does not make a PBMA product ultra-processed by default. To test our hypothesis, we conducted a randomised controlled trial to assess the changes to the gut microbiota of a group of 20 participants who replaced several meat-containing meals per week with meals cooked with PBMA products and compared these changes to those experienced by a size-matched control. Stool samples were subjected to 16S rRNA sequencing. The resulting raw data was analysed in a compositionality-aware manner, using a range of innovative bioinformatic methods. Noteworthy changes included an increase in butyrate metabolising potential—chiefly in the 4-aminobutyrate/succinate and glutarate pathways—and in the joint abundance of butyrate-producing taxa in the intervention group compared to control. We also observed a decrease in the Tenericutes phylum in the intervention group and an increase in the control group. Based on our findings, we concluded that the occasional replacement of animal meat with PBMA products seen in flexitarian dietary patterns can promote positive changes in the gut microbiome of consumers.

An extensive body of evidence documents the importance of the gut microbiome both in health and in a variety of human diseases. Cell and animal studies describing this relationship abound, whilst clinical studies exploring the associations between changes in gut microbiota and the corresponding metabolites with neurodegeneration in the human brain have only begun to emerge more recently. Further, the findings of such studies are often difficult to translate into simple clinical applications that result in measurable health outcomes. The purpose of this paper is to appraise the literature on a select set of faecal biomarkers from a clinician’s perspective. This practical review aims to examine key physiological processes that influence both gastrointestinal, as well as brain health, and to discuss how tools such as the characterisation of commensal bacteria, the identification of potential opportunistic, pathogenic and parasitic organisms and the quantification of gut microbiome biomarkers and metabolites can help inform clinical decisions of nutrition and lifestyle medicine practitioners.

Background: Dietary interventions have been previously explored in children with ADHD. Elimination diets and supplementation can produce beneficial behaviour changes, but little is known about the mechanisms mediating change. We propose that these interventions may work, in part, by causing changes in the gut microbiota. A microbiome-targeted dietary intervention was developed, and its feasibility assessed. Methods: A non-randomised feasibility study was conducted on nine non-medicated children with ADHD, aged 8–13 years (mean 10.39 years), using a prospective one-group pre-test/post-test design. Participants were recruited from ADHD support groups in London and took part in the 6-week microbiome-targeted dietary intervention, which was specifically designed to impact the composition of gut bacteria. Children were assessed pre- and post-intervention on measures of ADHD symptomatology, cognition, sleep, gut function and stool-sample microbiome analysis. The primary aim was to assess the study completion rate, with secondary aims assessing adherence, adverse events (aiming for no severe and minimal), acceptability and suitability of outcome measures. Results: Recruitment proved to be challenging and despite targeting 230 participants directly through support groups, and many more through social media, nine families (of the planned 10) signed up for the trial. The completion rate for the study was excellent at 100%. Exploration of secondary aims revealed that (1) adherence to each aspect of the dietary protocol was very good; (2) two mild adverse events were reported; (3) parents rated the treatment as having good acceptability; (4) data collection and outcome measures were broadly feasible for use in an RCT with a few suggestions recommended; (5) descriptive data for outcome measures is presented and suggests that further exploration of gut microbiota, ADHD symptoms and sleep would be helpful in future research. Conclusions: This study provides preliminary evidence for the feasibility of a microbiome-targeted dietary intervention in children with ADHD. Recruitment was challenging, but the diet itself was well-tolerated and adherence was very good. Families wishing to trial this diet may find it an acceptable intervention. However, recruitment, even for this small pilot study, was challenging. Because of the difficulty experienced recruiting participants, future randomised controlled trials may wish to adopt a simpler dietary approach which requires less parental time and engagement, in order to recruit the number of participants required to make meaningful statistical interpretations of efficacy. Trial registration: ClinicalTrials.gov Identifier: NCT03737877. Registered 13 November 2018—retrospectively registered, within 2 days of the first participant being recruited.

Introduction Current interventions for children with attention-deficit/hyperactivity disorder (ADHD) are primarily medication, behavioural therapy and parent training. However, research suggests dietary manipulations may provide therapeutic benefit for some. There is accumulating evidence that the gut microbiome may be atypical in ADHD, and therefore, manipulating gut bacteria in such individuals may help alleviate some of the symptoms of this condition. The aim of this study is to explore the effects of supplementation with kefir (a fermented dairy drink) on ADHD symptomatology, sleep, attention and the gut microbiome in children diagnosed with ADHD. Methods and analysis A 6-week randomised, double-blind, placebo-controlled trial in 70 children aged 8–13 years diagnosed with ADHD. Participants will be recruited throughout the UK, through support groups, community groups, schools, social media and word of mouth. Children will be randomised to consume daily either dairy kefir or a placebo dairy drink for 6 weeks. The primary outcome, ADHD symptomatology, will be measured by The Strengths and Weakness of ADHD-symptoms and Normal-behaviour scale. Secondary outcomes will include gut microbiota composition (using shotgun metagenomic microbiome sequencing), gut symptomatology (The Gastrointestinal Severity Index questionnaire), sleep (using 7-day actigraphy recordings, The Child’s Sleep Habits Questionnaire and Sleep Self Report questionnaire), inattention and impulsivity (with a computerised Go/NoGo test). Assessments will be conducted prior to the intervention and at the end of the intervention. Interaction between time (preintervention/postintervention) and group (probiotic/placebo) is to be analysed using a Mixed Model Analysis of Variances. Ethics and dissemination Ethical approval for the study was granted by St Mary’s University Ethics Committee. Results will be disseminated through peer-reviewed publications, presentations to the scientific community and support groups. Trial registration number NCT05155696.

Objective: To obtain a set of reference values for the intake of different types of dietary fibre in a healthy UK population.Design: This descriptive cross-sectional study used the UK Biobank data to estimate the dietary patterns of healthy individuals. Data on fibre content in different foods were used to calculate the reference values which were then calibrated using real-world data on total fibre intake.Setting: UK Biobank is a prospective cohort study of over 500 000 individuals from across the United Kingdom with the participants aged between 40 and 69 years.Participants: UK Biobank contains information on over 500 000 participants. This study was performed using the data on 19 990 individuals (6941 men, 13 049 women) who passed stringent quality control and filtering procedures and had reported above-zero intake of the analysed foods.Results: A set of reference values for the intake of six different types of soluble and insoluble fibres (cellulose, hemicelluloses, pectin and lignin), including the corresponding totals, was developed and calibrated using real-world data.Conclusions: To our knowledge, this is the first study to establish specific reference values for the intake of different types of dietary fibre. It is well known that effects exerted by different types of fibre both directly and through modulation of microbiota are numerous. Conceivably, a deficit or excess intake of specific types of dietary fibre may detrimentally affect human health. Filling this knowledge gap opens new avenues for research in discussion in studies of nutrition and microbiota and offers valuable tools for practitioners worldwide.