Background: There is mounting evidence that individuals with kidney disease and kidney stones have an abnormal gut microbiota composition. No studies to date have summarised the evidence to categorise how the gut microbiota profile of these individuals may differ from controls. Synthesis of this evidence is essential to inform future clinical trials. This systematic review aims to characterise differences of the gut microbial community in adults with kidney disease and kidney stones, as well as to describe the functional capacity of the gut microbiota and reporting of diet as a confounder in these studies. Methods: Included studies were those that investigated the gut microbial community in adults with kidney disease or kidney stones and compared this to the profile of controls. Six scientific databases (CINHAL, Medline, PubMed, Scopus, Web of Science and Cochrane Library), as well as selected grey literature sources, were searched. Quality assessment was undertaken independently by three authors. The system of evidence level criteria was employed to quantitatively evaluate the alteration of microbiota by strictly considering the number, methodological quality and consistency of the findings. Additional findings relating to altered functions of the gut microbiota, dietary intakes and dietary methodologies used were qualitatively summarised. Results: Twenty-five articles met the eligibility criteria and included data from a total of 892 adults with kidney disease or kidney stones and 1400 controls. Compared to controls, adults with kidney disease had increased abundances of several microbes including Enterobacteriaceae, Streptococcaceae, Streptococcus and decreased abundances of Prevotellaceae, Prevotella, Prevotella 9 and Roseburia among other taxa. Adults with kidney stones also had an altered microbial composition with variations to Bacteroides, Lachnospiraceae NK4A136 group, Ruminiclostridium 5 group, Dorea, Enterobacter, Christensenellaceae and its genus Christensenellaceae R7 group. Differences in the functional potential of the microbial community between controls and adults with kidney disease or kidney stones were also identified. Only three of the 25 articles presented dietary data, and of these studies, only two used a valid dietary assessment method. Conclusions: The gut microbiota profile of adults with kidney disease and kidney stones differs from controls. Future study designs should include adequate reporting of important confounders such as dietary intake to assist with interpretation of findings.

There is increasing evidence linking the gut microbiota to various aspects of human health. Nuts are a food rich in prebiotic fibre and polyphenols, food components which have been shown to have beneficial effects on the gut microbiota. This systematic review aimed to synthesise the evidence regarding the effect of nut consumption on the human gut microbiota. A systematic search of the databases MEDLINE, PubMed, Cochrane CENTRAL and CINAHL was performed until 28 November 2019. Eligible studies were those that investigated the effects of nut consumption in humans (aged over 3 years old), utilising next-generation sequencing technology. Primary outcome measures were between-group differences inα- andβ-diversity metrics and gut microbial composition. A total of eight studies were included in the review. Included studies assessed the effects of either almonds, walnuts, hazelnuts or pistachios on the gut microbiota. Overall, nut consumption had a modest impact on gut microbiota diversity, with two studies reporting a significant shift inα-diversity and four reporting a significant shift inβ-diversity. Walnuts, in particular, appeared to more frequently explain shifts inβ-diversity, which may be a result of their unique nutritional composition. Some shifts in bacterial composition (including an increase in genera capable of producing SCFA:Clostridium, Roseburia,LachnospiraandDialister) were reported following the consumption of nuts. Nut intake may yield a modulatory effect on the gut microbiota; however, results were inconsistent across studies, which may be explained by variations in trial design, methodological limitations and inter-individual microbiota.

Context: Dietary modifications can improve cardiovascular disease (CVD) risk factors. Personalized nutrition (PN) refers to individualized nutrition care based on genetic, phenotypic, medical, behavioral, and/or lifestyle characteristics. PN may be beneficial in improving CVD risk factors, including diet. However, this has not been reviewed previously. Objective: The aim was to evaluate the effectiveness of PN interventions on CVD risk factors and diet in adults at elevated CVD risk. Data Sources: Six databases were searched for randomized controlled trials published between 2000 and 2023 that tested the impact of PN interventions on CVD risk factors in people at elevated risk. Data Extraction: Risk of bias was assessed using the Academy of Nutrition and Dietetics Quality Criteria checklist. Data synthesis of eligible articles included participant characteristics, intervention details, and change in primary CVD risk factor outcomes, including blood pressure (BP), plasma lipids, and CVD risk score, and secondary risk factors, including anthropometric outcomes and diet quality. Random-effects meta-analyses were conducted to explore weighted mean differences (WMDs) in change or final mean values for studies with comparable data (studies with dietary counseling interventions) for outcomes including BP, blood lipids, and anthropometric measurements. Data Analysis: Of 7676 identified articles, 16 articles representing 15 studies met the inclusion criteria. Studies included between 40 and 563 participants and reported outcomes for CVD risk factors, including hyperlipidemia (n = 5), elevated BP (n = 3), overweight/obesity (n = 1), and multiple risk factors (n = 6). Risk of bias was low. Results suggested potential benefit of PN on systolic BP (WMD: −1.91; 95% CI: −3.51, −0.31 mmHg) and diastolic BP (WMD: −1.49; 95% CI: −2.39, −0.58 mmHg) and dietary intake in individuals at high CVD risk. Results were inconsistent for plasma lipid and anthropometric outcomes. Conclusion: Results were promising for PN interventions that used dietary counseling on CVD risk factors in at-risk individuals. However, further evidence for other personalization methods is required, including improving methodological quality and longer study duration in future PN interventions. Systematic Review Registration: OpenScience Framework (https://doi.org/10.17605/OSF.IO/SHVWP).

This review aimed to synthesise existing literature on the efficacy of personalised or precision nutrition (PPN) interventions, including medical nutrition therapy (MNT), in improving outcomes related to glycaemic control (HbA1c, post-prandial glucose [PPG], and fasting blood glucose), anthropometry (weight, BMI, and waist circumference [WC]), blood lipids, blood pressure (BP), and dietary intake among adults with prediabetes or metabolic syndrome (MetS). Six databases were systematically searched (Scopus, Medline, Embase, CINAHL, PsycINFO, and Cochrane) for randomised controlled trials (RCTs) published from January 2000 to 16 April 2023. The Academy of Nutrition and Dietetics Quality Criteria were used to assess the risk of bias. Seven RCTs (n = 873), comprising five PPN and two MNT interventions, lasting 3–24 months were included. Consistent and significant improvements favouring PPN and MNT interventions were reported across studies that examined outcomes like HbA1c, PPG, and waist circumference. Results for other measures, including fasting blood glucose, HOMA-IR, blood lipids, BP, and diet, were inconsistent. Longer, more frequent interventions yielded greater improvements, especially for HbA1c and WC. However, more research in studies with larger sample sizes and standardised PPN definitions is needed. Future studies should also investigate combining MNT with contemporary PPN factors, including genetic, epigenetic, metabolomic, and metagenomic data.

Key Points: Increasing plant diversity (≥30 plant foods/wk) reduced symptom burden and shifted the gut microbiome toward beneficial metabolite production. Increasing plant diversity was more effective for individuals with more advanced kidney disease and higher levels of uremic toxins at baseline. Increasing plant diversity, in addition to usual diet care, resulted in a substantial reduction in potential renal acid load of 47%. Background: Research suggests that eating a plant-dominant dietary pattern is beneficial to people with CKD. The aim was to investigate how increasing the diversity of plant food intake would affect metabolomic, microbiome, and clinical parameters in people with CKD. Methods: This study was a cross-over, randomized controlled trial involving 25 Australian adults diagnosed with stage 3–4 CKD. Participants were randomly allocated to follow two diets for 6 weeks each, separated by a minimum 4-week washout period: a high-diversity plant-based diet (HDPD, ≥30 unique plant foods weekly) and a low-diversity plant-based diet (LDPD, ≤15 unique plant foods weekly), alongside a usual kidney diet prescription. Data collection was completed at four time points (beginning and end of each intervention period). Primary outcome included a change in uremic toxins (indoxyl sulfate and p-cresyl sulfate) concentrations. Secondary and exploratory outcomes included diet quality and nutritional status, fecal microbiome composition and diversity, plasma metabolome, symptom burden, quality-of-life scores, BP, biochemical, and anthropometric measures. Results: Plasma and urinary uremic toxin levels did not consistently decrease across the cohort; however, significant reductions were observed in responders to the HDPD, particularly those with poorer kidney function and higher baseline uremic toxin levels. Neither diet caused electrolyte imbalances. The HDPD significantly improved diet quality, reduced potential renal acid load by an average of 47% from baseline, with an estimated marginal mean reduction of 9.96 (95% confidence interval, −16.28 to −3.64), and compared with the LDPD, decreased total symptom burden, including constipation (95% confidence interval, −4.11 to −0.54 and −0.91 to −0.22, respectively). It also shifted the gut microbiome toward increased production of beneficial metabolites such as butyrate/isobutyrate. By contrast, the LDPD reduced microbial diversity and decreased the abundance of 27 species and 33 functional genes. Conclusions: This study demonstrated the safety and clinically relevant therapeutic benefits of aiming to incorporate 30 or more unique plant foods weekly in the diet of individuals with moderate CKD. It was observed that individuals with more advanced kidney disease and higher levels of uremic toxins may derive the greatest benefit from adopting a HDPD. Clinical Trial registry name and registration number: ACTRN12619000442101.