Many adults report insufficient sleep duration and poor sleep quality. Interventions to improve sleep in adults are thus needed, and evidence suggests that diet could benefit sleep health. This review evaluates whether nutrients and bioactive compounds in pistachios could improve sleep. Pistachios are particularly rich in vitamin B6, magnesium, fibre, phenolic compounds, and phytomelatonin that could benefit sleep health. These nutrients are implicated in melatonin synthesis and gut–brain axis signalling of inhibitory neurons. Our evaluation of the literature indicates that pistachios could represent a promising wholefood intervention for improving sleep due to their favourable nutrient profile. However, human trials are needed to assess the direct effects of pistachio consumption on sleep outcomes.

Dietary fibre improves metabolic health, yet comparative evidence across different fibre sources remains unclear. This systematic review evaluates metabolic effects of oat β-glucan, rice bran, and unripe banana flour in adults, assessing glycaemic, lipid, and mechanistic effects, synthesising their physiological pathways across distinct fibre types (viscosity-driven, phytochemical-mediated, and resistant starch fermentation mechanisms). Following PRISMA 2020 guidelines, PubMed, Scopus, and Web of Science were searched up to June 2025. A total of 602 records were identified, and after removing 146 duplicates, 456 were screened. Forty-four full texts were assessed, and 15 studies were included. Risk of bias was evaluated using RoB 2.0 and Newcastle–Ottawa. Outcomes included glycaemic markers, insulin response, lipid profile, blood pressure, body composition, and mechanistic biomarkers. Studies (n = 15; sample sizes 10–154; durations 3 days–12 weeks) demonstrated heterogeneous dosing and formulations. Oat β-glucan consistently improved postprandial glucose, insulin AUC, and LDL-C, with modest effects on waist circumference and blood pressure. Rice bran improved blood lipids consistently, while glycaemic effects were mixed. UBF resistant starch was associated with reduction in fasting glucose, HOMA-IR, and body weight, although findings are based on small, short-duration trials. However, variability in study design and limited mechanistic assessments restricted cross-fibre synthesis. The available evidence suggests modest improvements in glycaemic and lipid outcomes. Differences in responsiveness likely reflect variations in fibre structure, viscosity, and fermentability, suggesting complementary physiological pathways. Standardised dosing, longer interventions, and mechanistic biomarkers – including SCFA profiles, incretin response, and bile acid signalling – are needed to clarify inter-individual variability and guide fibre-based interventions.

Gut micro-organisms possess biochemical capabilities that far exceed those of their mammalian hosts, particularly in the ability to gain energy from the breakdown of diet-derived plant material (fibre). This article reviews investigations into gut microbial communities conducted by Harry Flint and his research group. First, extracellular cellulosome and amylosome enzyme complexes were found to mediate the breakdown of plant cell walls and resistant starch by specialised Firmicutes bacteria, both in the human colon and in the rumen. In contrast, Bacteroidetes (Bacteroides, Prevotella spp.) rely on their ability to capture soluble carbohydrates. Human dietary studies examining the impact of fibre sources upon microbiota composition and metabolism identified ‘diet-responsive’ species. In addition, dominant species of butyrate-producing bacteria, including a subset able to convert lactate to butyrate, were isolated from healthy human volunteers. Most produce butyrate from carbohydrates via butyryl-CoA:acetate CoA-transferase, with uptake of external acetate, while lactate conversion is associated with a highly inducible gene cluster (lct). In pH-controlled chemostat studies, mildly acid pH depressed growth of propionate-producing Bacteroidetes, but favoured butyrate production by Firmicutes. This may explain why % butyrate among SCFA increases with total faecal SCFA concentration in human studies. Although lactate is normally consumed by lactate-utilising bacteria, destabilisation of the microbial community associated with lactate accumulation can result in radically altered microbiota and metabolite profiles. A theoretical model based on microbial functional groups (MFG) was developed to better understand community dynamics. Consequences for nutritional research of our expanding knowledge of the microbial ecology of the human gut are considered.

Current fibre recommendations are based on historical data and may underestimate the intake required for optimal cardiometabolic protection. We examined whether fibre intakes exceeding current guidelines are associated with additional improvements in inflammation and lipid metabolism. We analysed data from 7008 adults (≥ 20 years) from the National Health and Nutrition Examination Survey 2015–2018 with 24-h dietary recall and biomarker data (C-reactive protein (CRP), total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglycerides (TAG)). Fibre intake was expressed relative to recommendations from the Institute of Medicine (IOM) and the Academy of Nutrition and Dietetics (AND), and associations with biomarkers were assessed using multivariable regression models. Higher fibre intake was consistently associated with lower CRP concentrations, with the greatest reductions observed at intakes > 150 % of the IOM recommendation (> 55·7 g/d; 95 % CI: 48·6, 56·7). Among men, both TC and LDL-cholesterol decreased significantly at intakes > 150 % of IOM values (> 69·8 g/d; 95 % CI: 64·2, 75·4). TAG were significantly lower when fibre intake exceeded AND recommendations (> 41·0 g/d; 95 % CI: 32·6, 49·5). No clear associations were observed for HDL-cholesterol. The associations found in this study make us consider the possibility that the benefits of fibre on systemic inflammation and lipid profile may extend beyond current recommended levels. Public health guidelines may need to reconsider fibre targets to better reflect condition-specific benefits rather than minimum thresholds for adequacy should this hypothesis be duly proven by future longitudinal studies.

This review highlights the importance of dietary fibres (DF) intake and its interconnection with the gut microbiome and psychological well-being, while also exploring the effects of existing DF interventions on these aspects in adults. The gut microbiota is a complex and diverse ecosystem in which microbial species interact, influencing the human host. DF are heterogeneous, requiring different microbial species to degrade the complex DF structures. Emerging evidence suggests that microbial fermentation of DF produces short-chain fatty acids (SCFA), which may play a role in regulating psychological well-being by affecting neurotransmitter levels, including serotonin. The effectiveness of DF interventions depends on factors such as baseline gut microbiota composition, the dosage and the source of DF consumed. Although the gut microbiota of adults is relatively stable, studies have shown that the abundance of the species in the gut microbiota can change within 24 h of an intervention and may return to baseline following the termination of DF intervention. This review underscores the need for larger and well-powered dietary clinical trials incorporating longitudinal biological sample collections, advanced sequencing and omic techniques (including novel dietary biomarkers and microbial metabolites), validated subjective questionnaires and dietary records. Furthermore, mechanistic studies driven by clinical observations are crucial to understanding gut microbiota function and its underlying biological pathways, informing targeted dietary interventions.

Recommended dietary fibre consumption is rarely met in high-income countries. Detailed analysis of fibre consumption patterns is essential to identify strategies for increasing intake. This study investigated the timing and sources of fibre intake in Switzerland, using data from the Swiss Nutrition Survey, menuCH (n = 2057, 18–75 years). Dietary characteristics were summarised for the adult population and for subgroups stratified by absolute (< 15 g/day, 15-<30 g/day, and >=30 g/day) and relative (< 10 g/1000 kcal/day, 10-<14 g/1000 kcal/day, and >=14 g/1000 kcal/day) fibre intake. Mean fibre intake of both 24 HDRs for each individual and contribution of food groups and timing (before breakfast, breakfast, during the morning, lunch, during the afternoon, dinner, after dinner/at night) was calculated. Fibre was mainly consumed at breakfast (4.1 g/day), lunch (6.0 g/day), and dinner (6.4 g/day). Intake at breakfast differed between the lowest and highest fibre intake groups by 6.4 g/day (absolute) and 4.3 g/day (relative). Breakfast skipping was more frequent among low-fibre intake groups (29% for absolute intake, 19% for relative intake) than in the overall population (15%). The main sources of dietary fibre were grain products (35.6%), followed by vegetables (18.3%) and fruits (18.2%), with whole grains accounting for 17.5% of grain intake. Legumes contributed only to 1% of total fibre intake. Public health efforts encouraging regular breakfast consumption, and intake of whole grains and legumes are recommended to improve fibre intake.

Pectin is composed of a group of complex polysaccharides that are naturally found in various plants and are associated with a range of beneficial health effects. Health outcomes from dietary pectin can vary depending on botanical origin, dietary dose and structure of pectin. The objective of this scoping review is to build a comprehensive overview of the current evidence available on intervention studies conducted in humans and to better understand the possible knowledge gaps in terms of structure–function relationships across the different health-related effects. PubMed and Embase databases were searched using PRISMA-ScR guidelines, yielding 141 references (from the initial 3704), representing 134 intervention studies performed between 1961 and 2022 that met inclusion criteria. Studies were divided into six categories, which included gut health, glycaemic response and appetite, fat metabolism, bioavailability of micronutrients, immune response and other topics. Review of these human intervention studies identified a variety of cohort characteristics and populations (life stage, health status, country), sources/types of pectin (i.e. citrus, sugarbeet, apple, other and non-defined), intervention timeframes (from one single intake to 168 d) and doses (0.1–50 g/d) that were tested for health outcomes in people. Gut health, post-prandial glucose regulation and maintenance of blood cholesterol represented the largest categories of studied outcomes. Further research to strengthen the structure–function relationships for pectin with health properties and associated outcomes is warranted and will benefit from a more precise description of physico-chemical characteristics and molecular compositions, such as degree of esterification, weight, degree of branching, viscosity, gel formation and solubility.

The UK population is living longer; therefore, promoting healthy ageing via positive nutrition could have widespread public health implications. Moreover, dietary fibre intake is associated with health benefits; however, intake is below UK recommendations (30 g/d). Utilising national dietary survey data can provide up-to-date information on a large representative cohort of UK older adults, so that tailored solutions can be developed in the future. This study used cross-sectional data from the National Diet and Nutrition Survey (years 2008–2009 to 2018–2019) for older adults’ (n 1863; 65–96 years) dietary fibre intake (three-to-four-day food diaries), top ten dietary fibre-rich foods, associated factors (demographics, dietary/lifestyle habits) and various health outcomes (anthropometric, blood and urine). Mean dietary fibre intake was 18·3 g/d (range: 2·9–55·1 g/d); therefore, below the UK dietary recommendations, with compliance at 5·7 %. In addition, there were five significant associations (P < 0·05) related to lower dietary fibre intake such as increasing age group, without own natural teeth, impaired chewing ability, lower education leaving age and poor general health. Older adults’ key foods containing dietary fibre were mainly based on convenience such as baked beans, bread and potatoes. Positively, higher dietary fibre consumption was significantly associated (P = 0·007) with reduced diastolic blood pressure. In summary, the benefits of dietary fibre consumption were identified in terms of health outcomes and oral health were key modulators of intake. Future work should focus on a life course approach and the role of food reformulation to help increase dietary fibre intake.

The effect of single dietary fibre (DF) on lowering uric acid (UA) level has been reported in the literature. However, the potential protective mechanism of DF against potassium oxybate-induced hyperuricaemia (HUA), as modelled by prophylactic administration, remains unclear. The data demonstrate that DF significantly decreased serum and cerebral tissue UA concentrations, inhibited xanthine oxidase expression and activity in the liver and reduced levels of creatinine and urea nitrogen in the serum. Additionally, it mitigated the deposition of amyloid-β in cerebral tissue. Correlation analysis showed that DF modulated the Toll-like receptor 4/NF-κB signalling pathway, attenuating oxidative stress and inflammatory responses in HUA mice. Additionally, DF helps to maintain the composition of the gut microbiota, reducing harmful Desulfovibrio and enriching beneficial Akkermansia and Ruminococcus populations. The results of the faecal metabolomics analysis indicate that DF facilitates the regulation of metabolic pathways involved in oxidative stress and inflammation. These pathways include pyrimidine metabolism, tryptophan metabolism, nucleotide metabolism and vitamin B6 metabolism. Additionally, the study found that DF has a preventive effect on anxiety-like behaviour induced by HUA. In summary, DF shows promise in mitigating HUA and cognitive deficits, primarily by modulating gut microbiota and metabolites.

Dietary fibre (DF) is a non-digestible nutrient which has important roles in the digestive system including mantaining regularity, and reducing the risk of certain cancers and non-communicable diseases, such as metabolic syndrome. Even though the positive health effects of DF have long been established, it has been shown that DF intake for children and adults in Australia is below the recommended range – less than 20% of adults met the suggested intake for reducing risk of chronic diseases(1). Plantago ovata, also known as psyllium, is widely used as DF supplement with evidence showing positive effects on weight control, hyperglycaemic response, cholesterol levels, and irritable bowel syndrome(2). P. ovata seed husk produces a highly viscous gel called mucilage when seeds are exposed to moisture. This mucilage is nearly pure DF and has an intricately layered structure which can be further fractionated and studied as a proxy for different gelling systems. Interestingly, Australia is home to many mucilage-producing Plantago species, most of which are underexplored and underutilised, but show remarkable gelling properties and hypoglycaemic potential(3). In this work, we compare structural and functional properties of fractionated DF from P. ovata, and two promising Australian native relatives, P. turrifera and P. drummondii, and their effect on enzymatic hydrolysis in potato starch gels. Using a 3-step fractionation method, we have separated distinct fractions and explored their individual properties(4). P. turrifera and P. drummondii have higher water absorbing capacity, DF yield, and viscosity compared to P. ovata. Monosaccharide composition of all three species is similar – they are highly substituted heteroxylans with minor pectic component. Notably, arabinose to xylose ratio in all species increases with further extraction steps, which is different from cereal arabinoxylans. In an attempt to explore impact of DF in starch-rich systems, we have fabricated DF-potato starch gels and measured enzymatic hydrolysis (with porcine pancreatic α-amylase), freeze-thaw stability, and colour change. Addition of DF reduced syneresis (water separation) during 15 day freeze-thaw cycle measurement, which can lead to prolonged storage stability and has positive implications for shelf life. Colour change was most noticeable when P. drumondii DF were added, while colour of P. ovata and P. turiferra DF gels was similar to control potato starch gel. Effects on α-amylase starch hydrolysis were significant as well, and depended on species and fractions. Certain DFs had impacts on constant k (speed of hydrolysis), while effects on the extent of hydrolysis are still being explored. In conclusion, utility of Australia native P. turrifera and P. drumondii DFs are evident when applied to starch gels, and should be further explored in food products such as bread to increase DF intake and possibly lower glycaemic index.

Uncontrolled hypertension is a primary cause of non-communicable diseases and death globally(1). The gut microbiota plays a role in hypertension and dietary interventions high in fibre have been shown to lower blood pressure (BP)(2). Not all participants respond to dietary fibre interventions, for reasons which are unclear. Here we aimed to identify responders of a high fibre intervention based on their baseline gut microbiome. Twenty treatment-naive participants with hypertension received either placebo or 40g per day of prebiotic acetylated and butyrylated high amylose maize starch (HAMSAB) supplementation for 3 weeks in a phase II randomised cross-over double-blind placebo-controlled trial. Blood pressure was monitored at baseline and each endpoint by 24-hour ambulatory BP monitoring, with those experiencing a reduction between timepoints of ≥ 2 mmHg classified as responders. Baseline stool samples were collected and the V4-V5 region of the 16S gene sequenced. Taxonomy was assigned by reference to the SILVA database. The MaAsLin2 package was used for assessing the relationship between baseline gut microbiota and response to dietary intervention. Overall participants had significant reduction in 24-hour systolic BP (–6.1 mmHg, p = 0.03), with 14 individuals classified as responders and six individuals as non-responders. 13 genera were found to be differentially abundant between responders and non-responders. Genera significantly enriched in responders included Dialister (β = 1.29, q = 1.921x10-134), Coprococcus (β = 1.26, q = 3.282x10-121), Bifidobacterium (β = 1.67, q = 1.11x10-81), Ruminococcus (β = 0.161, q = 1.11x10-8) and Roseburia (β = 0.82, q = 4.275x10-2). Participants who experienced a decrease in systolic BP following a dietary fibre intervention had increased level of bacterial genera known to contain species that produce short-chain fatty acids (e.g. Bifidobacterium, Roseburia and Ruminococcus) at baseline. These data suggest that baseline microbiota composition contributes to the response to dietary fibre intervention trials in people with hypertension.

A majority of Australians consume a limited range of different dietary fibres and insufficient total dietary fibre(1). This contributes to low intestinal microbial diversity and impaired microbial function, such as capability in producing beneficial metabolites like short-chain fatty acids (SCFA). This diet-induced dysbiosis is associated with poor gastrointestinal health and a broad range of non-communicable diseases(2). Our study aimed to determine whether one dietary change, substitution of white bread with a high fibre bread improves faecal microbial diversity and butyrate-producing capability. Twenty-six healthy adults completed a randomised, cross-over, single-blinded intervention. Over the two intervention phases separated with a 4-wk washout, participants consumed either 3 slices of a high fibre bread (Prebiotic Cape Seed Loaf with BARLEYmax®) or control white bread as part of the usual diet, each for 2 weeks. At the beginning and end of each intervention period, participants completed a 24-h diet recall, a gut symptoms rating questionnaire and provided a faecal sample for microbiome analysis. The composition of faecal microbiome was characterised using 16S rRNA amplicon sequencing (V3-V4) and a marker of butyrate synthesis capability, the faecal content of butyryl-CoA:acetate CoA-transferase (BCoAT) gene was assessed using Real-time PCR. The high fibre bread intervention increased the servings of whole grain from 1.5 to 4 per day and increased total dietary fibre intake to 40 g/d which was double the amount of fibre consumed by participants at baseline or during the white bread intervention. Compared to white bread, the high fibre bread increased richness and evenness (Shannon, p = 0.014) of the gut microbiota and increased the relative abundance of SCFA producing taxa Lachnospiracae ND3007 group (p <0.001, FDR = 0.019). In addition, the high-fibre bread tended to increase relative abundance of butyrate-producing genus Roseburia, and microbial BCoAT gene content compared to white bread. In conclusion, the substitution of white bread with high-fibre bread improved the diversity of gut microbiota, specific microbes involved in SCFA production and may enhance the butyrate production capability of gut microbiota in healthy adults.

Diarrhoea is common in enterally fed patients and can impact their nutritional and overall outcomes. This meta-analysis evaluates the potential benefits of fibre-supplemented (FS) feeds on incidence of diarrhoea and stool frequency in non-critically ill tube-fed adults. Databases including PubMed, Embase and CINAHL with full text were searched for randomised controlled trials (RCT) with adults on exclusive tube feeding, published until August 2022. The Cochrane Collaboration’s tool was used for quality assessment. Studies with published results on incidence of diarrhoea and stool frequency were analysed using RevMan 5. Thirteen RCT with 847 non-critically ill patients between 20 and 90 years old without diarrhoea at the onset of enteral feeding were included. Study duration ranged from 3 to 35 d. Nine papers investigated the incidence of diarrhoea where intervention group was given FS and control was given non-fibre-supplemented (NFS) enteral feeds. Those receiving FS feeds were significantly less likely to experience diarrhoea as compared with those using NFS feeds (OR 0·44; 95 % CI 0·20, 0·95; P = 0·04; I2 = 71 %). Combined analysis showed no differences in stool frequency in those receiving NFS feeds (SMD 0·32; 95 % CI −0·53, 1·16; P = 0·47; I2 = 90 %). Results should be interpreted with caution due to considerable heterogeneity between study population, assessment tool for diarrhoea, potential conflict of interest and short duration of studies. This meta-analysis shows that FS feeds can reduce the incidence of diarrhoea in non-critically ill adults; however, the effects of stool frequency remain debatable.

Only 6 to 8 % of the UK adults meet the daily recommendation for dietary fibre. Fava bean processing lead to vast amounts of high-fibre by-products such as hulls. Bean hull fortified bread was formulated to increase and diversify dietary fibre while reducing waste. This study assessed the bean hull: suitability as a source of dietary fibre; the systemic and microbial metabolism of its components and postprandial events following bean hull bread rolls. Nine healthy participants (53·9 ± 16·7 years) were recruited for a randomised controlled crossover study attending two 3 days intervention sessions, involving the consumption of two bread rolls per day (control or bean hull rolls). Blood and faecal samples were collected before and after each session and analysed for systemic and microbial metabolites of bread roll components using targeted LC-MS/MS and GC analysis. Satiety, gut hormones, glucose, insulin and gastric emptying biomarkers were also measured. Two bean hull rolls provided over 85 % of the daily recommendation for dietary fibre; but despite being a rich source of plant metabolites (P = 0·04 v. control bread), these had poor systemic bioavailability. Consumption of bean hull rolls for 3 days significantly increased plasma concentration of indole-3-propionic acid (P = 0·009) and decreased faecal concentration of putrescine (P = 0·035) and deoxycholic acid (P = 0·046). However, it had no effect on postprandial plasma gut hormones, bacterial composition and faecal short chain fatty acids amount. Therefore, bean hulls require further processing to improve their bioactives systemic availability and fibre fermentation.

The current definition of dietary fibre was adopted by the Codex Alimentarius Commission in 2009, but implementation requires updating food composition databases with values based on appropriate analysis methods. Previous data on population intakes of dietary fibre fractions are sparse. We studied the intake and sources of total dietary fibre (TDF) and dietary fibre fractions insoluble dietary fibre (IDF), dietary fibre soluble in water but insoluble in 76 % aqueous ethanol (SDFP) and dietary fibre soluble in water and soluble in 76 % aqueous ethanol (SDFS) in Finnish children based on new CODEX-compliant values of the Finnish National Food Composition Database Fineli. Our sample included 5193 children at increased genetic risk of type 1 diabetes from the Type 1 Diabetes Prediction and Prevention birth cohort, born between 1996 and 2004. We assessed the intake and sources based on 3-day food records collected at the ages of 6 months, 1, 3 and 6 years. Both absolute and energy-adjusted intakes of TDF were associated with age, sex and breast-feeding status of the child. Children of older parents, parents with a higher level of education, non-smoking mothers and children with no older siblings had higher energy-adjusted TDF intake. IDF was the major dietary fibre fraction in non-breastfed children, followed by SDFP and SDFS. Cereal products, fruits and berries, potatoes and vegetables were major food sources of dietary fibre. Breast milk was a major source of dietary fibre in 6-month-olds due to its human milk oligosaccharide content and resulted in high SDFS intakes in breastfed children.