Postbiotics are functional bioactive compounds, generated in a matrix during fermentation, which may be used to promote health. The term postbiotics can be regarded as an umbrella term for all synonyms and related terms of these microbial fermentation components. Therefore, postbiotics can include many different constituents including metabolites, short-chain fatty acids (SCFAs), microbial cell fractions, functional proteins, extracellular polysaccharides (EPS), cell lysates, teichoic acid, peptidoglycan-derived muropeptides and pili-type structures. Postbiotics is also a rather new term in the ‘-biotics’ field. Where consensus exists for the definitions of pre- and probiotics, this is not yet the case for postbiotics. Here we propose a working definition and review currently known postbiotic compounds, their proposed mechanisms, clinical evidence and potential applications. Research to date indicates that postbiotics can have direct immunomodulatory and clinically relevant effects and evidence can be found for the use of postbiotics in healthy individuals to improve overall health and to relief symptoms in a range of diseases such as infant colic and in adults atopic dermatitis and different causes of diarrhea.

The bacteria received upon birth are the start of colonization of the approximately 1014 bacteria that are present in the mature human gastrointestinal tract, better known as the microbiota. The gut microbiota is implicated in gastrointestinal health, nutrient metabolism and benefits such as prevention of infection. Dietary fiber, including prebiotics, escape digestion in the small intestine and reach the colon intact, where they are partially or completely fermented by the gut microbiota. Areas covered: The possible interactions between dietary fiber, prebiotics and microbiota are discussed as well as how this relates to functional gastrointestinal disorders. During the first years of life the microbiota have not yet reached a stable state and is sensitive to disturbance by environmental factors. An imbalance in the microbiota early in life is found to be associated with several functional gastrointestinal disorders such as colic, functional abdominal pain, irritable bowel syndrome and constipation. Expert commentary: A better understanding of how gut microbial changes in early-life can impact gastrointestinal health might lead to new treatments or disease prevention. Nutritional strategies with fiber or prebiotics may support health due to modification of colonic microbiota composition and metabolic activity, for example by growth stimulation of Bifidobacterium and Lactobacillus.

Objective: The objective of this study was to investigate the effect of probiotics on functional abdominal pain disorders (FAPD) and functional constipation (FC). Methods: A systematic review was conducted, searching PubMed and Cochrane databases from inception to January 2018 for randomized controlled trials (RCTs) investigating the efficacy of probiotics in children aged 4 to 18 years with FAPD or children aged 0 to 18 years with FC. Results: A total of 657 citations were identified. Finally, 11 RCTs for FAPD and 6 RCTs for FC were included. Some evidence exists for Lactobacillus rhamnosus GG (n=3) in reducing frequency and intensity of abdominal pain in children with irritable bowel syndrome. There is no evidence to recommend L. reuteri DSM 17938 (n=5), a mix of Bifidobacterium infantis, Bifidobacterium breve and Bifidobacterium longum (n=1), Bifidobacterium lactis (n=1) or VSL#3 (n=1) for children with FAPD. No evidence exists to support the use of Lactobacillus casei rhamnosus LCR35 (n=1), B. lactis DN173 010 (n=1), B. longum (n=1), L. reuteri DSM 17938 (n=1), a mix of B. infantis, B. breve and B. longum (n=1), or Protexin mix (n=1) for children with FC. In general, studies had an unclear or high risk of bias. Conclusions: Insufficient evidence exists for the use of probiotics in FAPD and FC, only L. rhamnosus GG seems to reduce frequency and intensity of abdominal pain but only in children with irritable bowel syndrome. A better understanding of differences in gut microbiota in health and disease might lead to better probiotic strategies to treat disease.

Background and Aims. Ulcerative colitis (UC) is associated with an increased intestinal permeability, possibly through a dysbiosis of intestinal bacteria. We investigated which markers are most relevant to assess intestinal permeability in UC patients and whether probiotics had an effect on these markers. Methods. In this twelve-week placebo-controlled randomized double-blind study, twenty-five subjects with UC in remission received either placebo or a multispecies probiotics. Samples of blood, urine, and faeces were taken at baseline, week 6, and week 12 to assess intestinal permeability and inflammation. Diaries and Bristol stool scale were kept to record stool frequency and consistency. Quality of life was scored from 32–224 with the inflammatory bowel disease questionnaire (IBD-Q). Results. This group of UC patients, in clinical remission, did not show increased intestinal permeability at baseline of this study. During the study, no significant group or time effects were found for intestinal permeability measured by the 5-sugar absorption test, serum zonulin, and faecal zonulin. Likewise, the inflammatory markers C-reactive protein (CRP), calprotectin, and the cytokines IFNγ, TNFα, IL-6, and IL-10 were not significantly affected. Stool frequency and consistency were not significantly affected either. The IBD-Q score, 194 for the probiotics group and 195 for the placebo group, remained unaffected. Correlations were tested between all outcomes; urinary sucrose excretion was significantly correlated with serum zonulin (r = 0.62) and faecal calprotectin (r = 0.55). Faecal zonulin was not significantly correlated with any of the other markers. Conclusion. Serum zonulin may be a more relevant biomarker of intestinal permeability than faecal zonulin, due to its correlation with other biomarkers of intestinal permeability. UC patients in remission did not show an effect of the probiotic treatment or a change in gut permeability. This should not discourage further studies because effects might be present during active disease or shortly after a flare up.

Objective: The aim of the study was to assess whether the modified Bristol Stool Form Scale (m‐BSFS) is reliable, valid and user‐friendly to use by parents, grandparents, and day childcare employees to evaluate stool consistency in toilet and nontoilet‐trained toddlers in the Netherlands.Study design: Translation to Dutch and validity of the m‐BSFS (scoring 32 general stool pictures) for 1 to 3 year old toddlers (n = 89) was evaluated by parents, grandparents, and day childcare employees. A subgroup of participants scored an additional 7 pictures of stools in a diaper to validate the m‐BSFS for non‐toilet‐trained toddlers (n = 16). To determine inter‐rater reliability, 2‐way random effects single‐rater intraclass correlation coefficient (ICC)_consistency was used. Intra‐rater reliability was measured by Cohen kappa (κ) by rating the same pictures in random order twice, with at least 1 week between the first and second scoring.Results: Inter‐ and intra‐rater reliability of the m‐BSFS were above recommended minimal standards of 0.61 for the 32 general stool pictures as well as for the 7 pictures of stools in a diaper. ICC_consistency for the general stool pictures of the first and second ratings were 0.71 (n = 89) and 0.79 (n = 77), respectively, with a κ of 0.71 (n = 77). ICC_consistency for the stools in diaper pictures of the first and second ratings were 0.93 (n = 16) and 0.93 (n = 15), respectively, with a κ of 0.77 (n = 15).Conclusions: The m‐BSFS is reliable, valid and user‐friendly to use by Dutch‐speaking parents, grandparents, and day childcare workers to evaluate stool consistency in both toilet‐ and nontoilet‐trained toddlers in the Netherlands.

Background: Functional constipation (FC) in children is a common gastrointestinal disorder with a worldwide-pooled prevalence of 9.5%. Complaints include infrequent bowel movements, painful defecation due to hard and/or large stools, faecal incontinence, and abdominal pain. Prebiotic oligosaccharides have been shown to relieve constipation symptoms in young adults and elderly. However, sufficient evidence is lacking linking additional prebiotic intake to improve symptoms in children with FC. We hypothesise that prebiotic oligosaccharides are able to relieve symptoms of constipation in young children as well. Methods: In the present randomised, double-blind, placebo-controlled, multi-centre study, we will study the effects of two prebiotic oligosaccharides in comparison to placebo on constipation symptoms in children of 1–5 years (12 to 72 months) of age diagnosed with FC according to the Rome IV criteria for functional gastrointestinal disorders. The primary outcome measure will be change in stool consistency. Secondary outcomes include stool frequency and stool consistency in a number of cases (%). Tertiary outcomes include among others painful defecation, use of rescue medication, and quality of life. In addition, the impact on gut microbiome outcomes such as faecal microbiota composition and metabolites will be investigated. Participants start with a run-in period, after which they will receive supplements delivered in tins with scoops for 8 weeks, containing one of the two prebiotic oligosaccharides or placebo, followed by a 4-week wash-out period. Discussion: This randomised double-blind, placebo-controlled multi-centre study will investigate the effectiveness of prebiotic oligosaccharides in children aged 1–5 years with FC. Trial registration: ClinicalTrials.gov NCT04282551. Registered on 24 February 2020.