β2-1 Fructan supplementation alters host immune responses in a manner consistent with increased exposure to microbial components: results from a double-blinded, randomised, cross-over study in healthy adults

A survey into the utilization of probiotics and medicinal plants among individuals afflicted with gastrointestinal disorders in healthcare institutions in Saïda, Algeria

Aim: Functional gastrointestinal (GI) disorders are recognized as a major public health concern worldwide. These disorders involve persistent digestive symptoms indicative of digestive tract dysfunction.Materials and Methods: A survey examining the utilisation of probiotics and medicinal plants as supplementary treatments was conducted on 160 patients with GI disorders at healthcare institutions in Saïda from March to April 2023 using questionnaires that had been previously adapted and tested for reliability with Cronbach's alpha test. Raw data collected through the questionnaires were transferred to a database and analysed using SPSS software.Results: Overall, 49.38% of participants possessed knowledge of or actively utilised probiotics; such awareness was strongly associated with the participants' educational attainment (p = 0.029). The noteworthy probiotic supplements were Biocharbon (36.09%), Lactocil (15.38%), Smebiocta (13.61%), Ultrabiotic Adult (12.43%), Effidigest (12.43%), and Ultralevure (7.69%). During crisis, individuals tended to consume natural goods rich in probiotics, including yoghurt (13.26%) and fermented milk (8.60%), as well as foods rich in prebiotic fibre, including vegetables (18.99%), fruits (13.26%), wheat (9.67%), bran (7.52%), rye (6.81%), and oat flakes (6.45%). Additionally, 77.56% of patients used medicinal plants during crises, with Mentha spicata (12.2%), Thymus vulgaris (11.3%), Pimpinella anisum (8.5%), Cuminum cyminum (8.0%), Punica granatum (7.8%), Trachyspermum ammi (7.5%), and Senna acutifolia (7.0%) being the more commonly favoured options in phytotherapy. The main focus of these herbs was to alleviate bloating (57%), constipation (30.12%), and diarrhoea (12.87%) (p < 0.001). The most frequently utilised plant parts were leaves (47.30%), seeds (25.21%), and bark (13.21%). Most patients (82.91%) favoured infusion as their preferred consumption method, and approximately 85.43% believed in phytotherapy's ability to extend symptomatic relief.Conclusion: The understanding of probiotics is still in its infancy, whereas phytotherapy is more widely accepted by patients. Nonetheless, patients are open to the exploration of natural alternatives to conventional medicines.

The gut microbiome and dietary fibres: implications in obesity, cardiometabolic diseases and cancer

Dietary fibres constitute a heterogeneous class of nutrients that are key in the prevention of various chronic diseases. Most dietary fibres are fermented by the gut microbiome and may, thereby, modulate the gut microbial ecology and metabolism, impacting human health. Dietary fibres may influence the occurrence of specific bacterial taxa, with this effect varying between individuals. The effect of dietary fibres on microbial diversity is a matter of debate. Most intervention studies with dietary fibres in the context of obesity and related metabolic disorders reveal the need for an accurate assessment of the microbiome to better understand the variable response to dietary fibres. Epidemiological studies confirm that a high dietary fibre intake is strongly associated with a reduced occurrence of many types of cancer. However, there is a need to determine the impact of intervention with specific dietary fibres on cancer risk, therapy efficacy and toxicity, as well as in cancer cachexia. In this Review, we summarize the mechanisms by which the gut microbiome can mediate the physiological benefits of dietary fibres in the contexts of obesity, cardiometabolic diseases and cancer, their incidence being clearly linked to low dietary fibre intake.

Effects of fructan and gluten on gut microbiota in individuals with self-reported non-celiac gluten/wheat sensitivity-a randomised controlled crossover trial

BACKGROUND

Individuals with non-celiac gluten/wheat sensitivity (NCGWS) experience improvement in gastrointestinal symptoms following a gluten-free diet. Although previous results have indicated that fructo-oligosaccharides (FOS), a type of short-chain fructans, were more likely to induce symptoms than gluten in self-reported NCGWS patients, the underlying mechanisms are unresolved.

METHODS

Our main objective was therefore to investigate whether FOS-fructans and gluten affect the composition and diversity of the faecal microbiota (16S rRNA gene sequencing), faecal metabolites of microbial fermentation (short-chain fatty acids [SCFA]; gas chromatography with flame ionization detector), and a faecal biomarker of gut inflammation (neutrophil gelatinase-associated lipocalin, also known as lipocalin 2, NGAL/LCN2; ELISA). In the randomised double-blind placebo-controlled crossover study, 59 participants with self-reported NCGWS underwent three different 7-day diet challenges with gluten (5.7 g/day), FOS-fructans (2.1 g/day), and placebo separately (three periods, six challenge sequences).

RESULTS

The relative abundances of certain bacterial taxa were affected differently by the diet challenges. After the FOS-fructan challenge, Fusicatenibacter increased, while Eubacterium (E.) coprostanoligenes group, Anaerotruncus, and unknown Ruminococcaceae genera decreased. The gluten challenge was primarily characterized by increased abundance of Eubacterium xylanophilum group. However, no differences were found for bacterial diversity (α-diversity), overall bacterial community structure (β-diversity), faecal metabolites (SCFA), or NGAL/LCN2. Furthermore, gastrointestinal symptoms in response to FOS-fructans were generally not linked to substantial shifts in the gut bacterial community. However, the reduction in E. coprostanoligenes group following the FOS-fructan challenge was associated with increased gastrointestinal pain. Finally, correlation analysis revealed that changes in gastrointestinal symptoms following the FOS-fructan and gluten challenges were linked to varying bacterial abundances at baseline.

CONCLUSIONS

In conclusion, while FOS-fructans induced more gastrointestinal symptoms than gluten in the NCGWS patients, we did not find that substantial shifts in the composition nor function of the faecal microbiota could explain these differences in the current study. However, our results indicate that individual variations in baseline bacterial composition/function may influence the gastrointestinal symptom response to both FOS-fructans and gluten. Additionally, the change in E. coprostanoligenes group, which was associated with increased symptoms, implies that attention should be given to these bacteria in future trials investigating the impact of dietary treatments on gastrointestinal symptoms.

TRIAL REGISTRATION

Clinicaltrials.gov as NCT02464150.

Fueling the success of transplantation through nutrition: recent insights into nutritional interventions, their interplay with gut microbiota and cellular mechanisms

PURPOSE OF REVIEW

The role of nutrition in organ health including solid organ transplantation is broadly accepted, but robust data on nutritional regimens remains scarce calling for further investigation of specific dietary approaches at the different stages of organ transplantation. This review gives an update on the latest insights into nutritional interventions highlighting the potential of specific dietary regimens prior to transplantation aiming for organ protection and the interplay between dietary intake and gut microbiota.

RECENT FINDINGS

Nutrition holds the potential to optimize patients' health prior to and after surgery, it may enhance patients' ability to cope with the procedure-associated stress and it may accelerate their recovery from surgery. Nutrition helps to reduce morbidity and mortality in addition to preserve graft function. In the case of living organ donation, dietary preconditioning strategies promise novel approaches to limit ischemic organ damage during transplantation and to identify the underlying molecular mechanisms of diet-induced organ protection. Functioning gut microbiota are required to limit systemic inflammation and to generate protective metabolites such as short-chain fatty acids or hydrogen sulfide.

SUMMARY

Nutritional intervention is a promising therapeutic concept including the pre- and rehabilitation stage in order to improve the recipients' outcome after solid organ transplantation.

The effects of inulin-type fructans on cardiovascular disease risk factors: systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Inulin-type fructans (ITF) are the leading prebiotics in the market. Available evidence provides conflicting results regarding the beneficial effects of ITF on cardiovascular disease risk factors.

OBJECTIVES

This study aimed to evaluate the effects of ITF supplementation on cardiovascular disease risk factors in adults.

METHODS

We searched MEDLINE, EMBASE, Emcare, AMED, CINAHL, and the Cochrane Library databases from inception through May 15, 2022. Eligible randomized controlled trials (RCTs) administered ITF or placebo (for example, control, foods, diets) to adults for ≥2 weeks and reported one or more of the following: low, very-low, or high-density lipoprotein cholesterol (LDL-C, VLDL-C, HDL-C); total cholesterol; apolipoprotein A1 or B; triglycerides; fasting blood glucose; body mass index; body weight; waist circumference; waist-to-hip ratio; systolic or diastolic blood pressure; or hemoglobin A1c. Two reviewers independently and in duplicate screened studies, extracted data, and assessed risk of bias. We pooled data using random-effects model, and assessed the certainty of evidence (CoE) using the Grading of Recommendations, Assessment, Development and Evaluation approach.

RESULTS

We identified 1767 studies and included 55 RCTs with 2518 participants in meta-analyses. The pooled estimate showed that ITF supplementation reduced LDL-C [mean difference (MD) -0.14 mmol/L, 95% confidence interval (95% CI: -0.24, -0.05), 38 RCTs, 1879 participants, very low CoE], triglycerides (MD -0.06 mmol/L, 95% CI: -0.12, -0.01, 40 RCTs, 1732 participants, low CoE), and body weight (MD -0.97 kg, 95% CI: -1.28, -0.66, 36 RCTs, 1672 participants, low CoE) but little to no significant effect on other cardiovascular disease risk factors. The effects were larger when study duration was ≥6 weeks and in pre-obese and obese participants.

CONCLUSION

ITF may reduce low-density lipoprotein, triglycerides, and body weight. However, due to low to very low CoE, further well-designed and executed trials are needed to confirm these effects.

PROSPERO REGISTRATION NUMBER

CRD42019136745.

The arsenic-lowering effect of inulin-type prebiotics in end-stage renal disease: a randomized crossover trial

Background: Circulatory imbalance of trace elements is frequent in end-stage renal disease (ESRD), leading to a deficiency of essential elements and excess of toxic elements. The present study aimed to investigate whether inulin-type fructans (ITFs) could ameliorate the circulatory imbalance by modulating gut microbiota and regulating the absorption and elimination of trace elements. Methods: Peritoneal dialysis patients were enrolled in a randomized crossover trial, undergoing interventions with ITFs (10 g d-1) and maltodextrin (placebo) over a 9-month period (with a 3-month washout). The primary outcomes included essential elements Mn, Fe, Co, Cu, Zn, Se, Sr, and Mo and potential toxic elements V, Cr, Ni, As, Cd, Ba, Tl, Pb, Th, and U in plasma. Secondary outcomes included the gut microbiome, short chain fatty acids (SCFAs), bile acids (BAs), and daily removal of trace elements through urine, dialysate and feces. Results: Among the 44 participants initially randomized, 29 completed the prebiotic, placebo or both interventions. The daily dietary intake of macronutrients and trace elements remained consistent throughout the study. The administration of 10 g d-1 ITFs significantly reduced plasma arsenic (As) by 1.03 μg L-1 (95%CI: -1.74, -0.33) (FDR-adjusted P = 0.045) down from the baseline of 3.54 μg L-1 (IQRs: 2.61-4.40) and increased the As clearance rate by urine and dialysis (P = 0.033). Positive changes in gut microbiota were also observed, including an increase in the Firmicutes/Bacteroidetes ratio (P = 0.050), a trend towards higher fecal SCFAs (P = 0.082), and elevated excretion of primary BAs (P = 0.035). However, there were no significant changes in plasma concentrations of other trace elements or their daily removal by urine, dialysis and feces. Conclusions: The daily administration of 10 g d-1 ITFs proved to be effective in reducing the circulating retention of As but demonstrated to be ineffective for other trace elements in ESRD. These sentences are ok to include but as "The clinical trial registry number is ChiCTR-INR-17013739 (https://www.chictr.org.cn/showproj.aspx?proj=21228)".

Effect of chicory-derived inulin-type fructans on abundance of Bifidobacterium and on bowel function: a systematic review with meta-analyses

Inulin-type fructans are considered to stimulate the growth of beneficial microorganisms, like Bifidobacterium in the gut and support health. However, both the fructan source and chemical structure may modify these effects. A systematic review was conducted to assess the effects of chicory-derived inulin-type fructans consumed either in specific foods or as dietary supplements on abundance of Bifidobacterium in the gut and on health-related outcomes. Three electronic databases and two clinical trial registries were systematically searched until January 2021. Two authors independently selected randomized controlled trials that investigated with a protocol of minimum seven days supplementation the effect of chicory-derived inulin-type fructans on Bifidobacterium abundance in any population. Meta-analyses with random-effects model were conducted on Bifidobacterium abundance and bowel function parameters. We evaluated risk of bias using Cochrane RoB tool. Chicory-derived inulin-type fructans at a dose of 3-20 g/day significantly increased Bifidobacterium abundance in participants with an age range from 0 to 83 years (standardized mean difference: 0.83, 95% CI: 0.58-1.08; p < 0.01; 50 studies; 2525 participants). Significant bifidogenic effects were observed in healthy individuals and in populations with health impairments, except gastrointestinal disorders. Significant beneficial effects on bowel function parameters were observed in healthy subjects. Chicory-derived inulin-type fructans may have significant bifidogenic effects and may beneficially influence bowel function in healthy individuals. PROSPERO registration number CRD42020162892.

Supplementation with inulin-type fructans affects gut microbiota and attenuates some of the cardiometabolic benefits of a plant-based diet in individuals with overweight or obesity

Background

The gut microbiota has emerged as a potential therapeutic target to improve the management of obesity and its comorbidities.

Objective

We investigated the impact of a high fiber (∼38 g/d) plant-based diet, consumed ad libitum, with or without added inulin-type fructans (ITF), on the gut microbiota composition and cardiometabolic outcomes in subjects with obesity. We also tested if baseline Prevotella/Bacteroides (P/B) ratio predicts weight loss outcomes.

Methods

This is a secondary exploratory analysis from the PREVENTOMICS study, in which 100 subjects (82 completers) aged 18-65 years with body mass index 27-40 kg/m2 were randomized to 10 weeks of double-blinded treatment with a personalized or a generic plant-based diet. Changes from baseline to end-of-trial in gut microbiota composition (16S rRNA gene amplicon sequencing), body composition, cardiometabolic health and inflammatory markers were evaluated in the whole cohort (n = 82), and also compared in the subgroup of subjects who were supplemented with an additional 20 g/d ITF-prebiotics (n = 21) or their controls (n = 22).

Results

In response to the plant-based diet, all subjects lost weight (-3.2 [95% CI -3.9, -2.5] kg) and experienced significant improvements in body composition and cardiometabolic health indices. Addition of ITF to the plant-based diet reduced microbial diversity (Shannon index) and selectively increased Bifidobacterium and Faecalibacterium (q < 0.05). The change in the latter was significantly associated with higher values of insulin and HOMA-IR and lower HDL cholesterol. In addition, the LDL:HDL ratio and the concentrations of IL-10, MCP-1 and TNFα were significantly elevated in the ITF-subgroup. There was no relationship between baseline P/B ratio and changes in body weight (r = -0.07, p = 0.53).

Conclusion

A plant-based diet consumed ad libitum modestly decreases body weight and has multiple health benefits in individuals with obesity. Addition of ITF-prebiotics on top this naturally fiber-rich background selectively changes gut microbiota composition and attenuates some of the realized cardiometabolic benefits.

Clinical trial registration

[https://clinicaltrials.gov/ct2/show/NCT04590989], identifier [NCT04590989].

The impact of diet on disease activity in spondyloarthritis: A systematic literature review

OBJECTIVES

Our study aimed to systematically review the evidence about the effect of diet or dietary supplements on spondyloarthritis (SpA) disease activity.

METHODS

a systematic literature review (SLR) was conducted in MEDLINE, EMBASE, Cochrane and SCOPUS according to the "PEO" format (Population, Exposure, Outcome). The population was SpA (axial or peripheral, axSpA/pSpA, including Psoriatic Arthritis-PsA); the intervention any kind of diet/dietary supplement; the outcome disease activity. Inclusion criteria were: adult patients, Randomized Controlled Trials (RCTs) and longitudinal studies (so that a pre-and post-intervention assessment were available), papers in English. Risk of bias (RoB) was conducted with different tools according to the design of the study.

RESULTS

Literature search yielded 1390 publications, of which 15 were finally inlcuded: 12 interventional and 3 observational studies. Among those with the lower RoB: a) 2 RCTs, one at unclear and one at low RoB, failed to show benefit of probiotics in SpA b) Two RCTs at unclear RoB provided evidence that weight loss, but not hypocaloric diet, was associated to MDA achievement in PsA. The remaining interventional studies were at high RoB. Among the observational studies, one study on Mediterranean diet demonstrated an association between diet adherence and a ≥ 20% decrease of ASDAS in axSpA. The other two observational studies were judged of poor quality.

CONCLUSIONS

weight loss seem to be able to impact disease activity in PsA, while probiotics do not seem useful in SpA; evidence for dietary behaviors is scarce and heterogeneous.

Short bouts of walking attenuates the response of IL-8 to prolonged sitting in healthy adults

PURPOSE

Experimental studies have shown that prolonged sitting for 2-8 h can cause changes to vascular and metabolic markers; the response of pro-inflammatory cytokines is relatively unexplored. The purpose of this study is to determine the response of interleukin-8 (IL-8) to prolonged and interrupted sitting.

METHODS

Healthy participants (n = 24, 21.1 years ± 2.2, 50% female) completed a prolonged sitting session (4 h) and an interrupted sitting session (4 h of sitting with 3 min of walking at 60%HRmax, every 30 min) in random order. Saliva and capillary plasma were collected at the beginning (T1) and at the end of each session (T2).

RESULTS

Salivary concentrations of IL-8 increased during the prolonged (T1 median: 22.09 pg/mL, T2 median: 86.18 pg/mL; p =  < 0.01, ES - 0.55) and interrupted (T1 median: 22.09 pg/mL, T2 median: 51.99 pg/mL; p = 0.021, ES - 0.34) sessions; however, the increase during interrupted sitting was lower (PS median: 134.4%, range: - 43.96 to 1115.69 and IS median: 50.8%, range: - 75.5 to 356.35; p = 0.011, ES - 0.53). In the sub-sample of males, salivary IL-8 did not increase in the interrupted session (T1 median: 22.09, range: 3.496-699.12, and T2 median: 24.96, range: 5.11-533.5, p =  > 0.05, ES - 0.16). No significant findings were observed for IL-8 in the plasma.

CONCLUSION

Prolonged sitting appears to increase concentrations of the pro-inflammatory cytokine IL-8 while interrupting this sitting with short bouts of walking blunts this response. Sex appears to moderate this relationship; however, there appears to be a large amount of individual variability.

High-fat diet promotes the effect of fructo-oligosaccharides on the colonic luminal environment, including alkaline phosphatase activity in rats

We recently reported that fermentable nondigestible carbohydrates such as oligosaccharides, commonly increase colonic alkaline phosphatase (ALP) activity and the gene expression of Alpi-1, coding for rat intestinal alkaline phosphatase-I isozyme in rats and that the effect of oligosaccharides on colonic ALP activity is affected by the quality of dietary fats. We hypothesized that the amount of dietary fat would modulate the effect of oligosaccharides on colonic ALP and luminal environment in rats. In experiment 1, male Sprague-Dawley rats were fed a low-fat (LF, 5% lard) or high-fat (HF, 30% lard) diet with or without 4% fructo-oligosaccharides (FOS). In experiment 2, they were fed a 2.5%, 7%, 20%, or 40% fat (lard) diet with 4% FOS for 2 weeks. Dietary FOS in the HF diet (HF-FOS) significantly increased ALP activity in the colon and cecal digesta and colonic expression of Alpi-1, but not in the LF diet with FOS groups (LF-FOS). In comparison to the LF-FOS group, the increases in fecal mucins, Lactobacillus ratio, as well as cecal n-butyrate, and the decrease in fecal Clostridium coccoides, were more pronounced in the HF-FOS group. Compared with the 2.5% or 7% fat + FOS diet, the 20% fat + FOS diet significantly increased colonic ALP activity, Alpi-1 expression, and fecal mucins. These factors did not differ significantly between 20% and 40% fat + FOS diets. To exert the maximum effect of FOS on the colonic luminal environment, including ALP activity in rats, significantly more fat may be required than that contained present a LF diet.

Interaction between dietary fiber and bifidobacteria in promoting intestinal health

Bifidobacteria are considered as probiotics due to their role in promoting intestinal health, including regulating intestinal flora, controlling glycolipid metabolism, anti-colitis effects. Dietary fiber is considered as prebiotic favoring gut health. It also can be used as carbon source to support the growth and colonization of probiotics like bifidobacteria. However, because of genetic diversity, different bifidobacterial species differ in their ability to utilize dietary fiber. Meanwhile, dietary fiber with different structural properties has different effects on the bifidobacteria proliferation. The interaction between dietary fiber and bifidobacteria will consequently lead to a synergistic or antagonistic function in promoting intestinal health, therefore affecting the application of combined use of dietary fiber and bifidobacteria. In this case, we summarize the biological function of bifidobacteria, and their interaction with different dietary fiber in promoting gut health, and finally provide several strategies about their combined use.

A Cohort Study of the Effects of Daily-Diet Water-Soluble Dietary Fiber on Butyric Acid-Producing Gut Microbiota in Middle-Aged and Older Adults in a Rural Region

Water-soluble dietary fiber is primarily a substrate for degradation of short chain fatty acids (SCFAs), particularly butyric acid, by gut microbiota. SCFAs have beneficial effects on the whole body. However, epidemiological studies on the association between water-soluble dietary fiber from daily food intake and butyric acid-producing bacteria are inconsistent. The purpose of this study was to determine the association between levels of water-soluble dietary fiber from daily food intake and gut microbiota, particularly butyric acid producers, in middle-aged and older adults in a rural area in Japan. We examined the effects of water-soluble dietary fiber intake on gut microbiota after adjusting for confounding factors. After propensity score matching, 520 subjects (260 in the low-intake group and 260 in the high-intake group) were selected. One year later after a follow-up survey, we re-classified the participants and again compared low- and high-intake groups. As a result, people with a high intake had a higher relative abundance of butyric acid-producing bacteria. It was also revealed that butyric acid-producing bacteria remained high in the group that maintained high intake the next year. We concluded that continuous intake of water-soluble dietary fiber from daily food is necessary to maintain sufficient amounts of butyric acid-producing bacteria.

Natural Variation in the Content and Degree of Polymerization of Fructans in Wheat: Potential for Selection of Genotypes with Beneficial Health Composition

Fructans are important biocompounds because of their health-promoting effects as dietary fiber and prebiotics and also because of their harmful effects as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) particularly in people suffering from irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), and recently as potential triggers of non-celiac wheat/gluten sensitivity. In this work, we have analyzed the fructan contents as well as its degree of polymerization (DP) in a genetically diverse set of wheat varieties, modern and landraces, from different commonly consumed species (N = 124). A significant variation in fructan contents within and between species was observed, with the following relationship: Triticum aestivum (Landraces) > Triticum aestivum (Modern) ≥ Triticum turgidum (Modern) = T. turgidum (Landraces) ≥ Triticum spelta. In addition, a substantial part of the fructans (>50%) showed a DP ≤ 6. Considering that wheat is a major source of fructans, our results can contribute to a better nutritional management of our diets and be a basis for targeted wheat breeding to alter fructan contents.

Validity of food additive maltodextrin as placebo and effects on human gut physiology: systematic review of placebo-controlled clinical trials

PURPOSE

Maltodextrin (MDX) is a polysaccharide food additive commonly used as oral placebo/control to investigate treatments/interventions in humans. The aims of this study were to appraise the MDX effects on human physiology/gut microbiota, and to assess the validity of MDX as a placebo-control.

METHODS

We performed a systematic review of randomized-placebo-controlled clinical trials (RCTs) where MDX was used as an orally consumed placebo. Data were extracted from study results where effects (physiological/microbial) were attributed (or not) to MDX, and from study participant outcomes data, before-and-after MDX consumption, for post-publication 're-analysis' using paired-data statistics.

RESULTS

Of two hundred-sixteen studies on 'MDX/microbiome', seventy RCTs (n = 70) were selected for analysis. Supporting concerns regarding the validity of MDX as a placebo, the majority of RCTs (60%, CI 95% = 0.48-0.76; n = 42/70; Fisher-exact p = 0.001, expected < 5/70) reported MDX-induced physiological (38.1%, n = 16/42; p = 0.005), microbial metabolite (19%, n = 8/42; p = 0.013), or microbiome (50%, n = 21/42; p = 0.0001) effects. MDX-induced alterations on gut microbiome included changes in the Firmicutes and/or Bacteroidetes phyla, and Lactobacillus and/or Bifidobacterium species. Effects on various immunological, inflammatory markers, and gut function/permeability were also documented in 25.6% of the studies (n = 10/42). Notably, there was considerable variability in the direction of effects (decrease/increase), MDX dose, form (powder/pill), duration, and disease/populations studied. Overall, only 20% (n = 14/70; p = 0.026) of studies cross-referenced MDX as a justifiable/innocuous placebo, while 2.9% of studies (n = 2/70) acknowledged their data the opposite.

CONCLUSION

Orally-consumed MDX often (63.9% of RCTs) induces effects on human physiology/gut microbiota. Such effects question the validity of MDX as a placebo-control in human clinical trials.

Microbiota responses to different prebiotics are conserved within individuals and associated with habitual fiber intake

BACKGROUND

Short-chain fatty acids (SCFAs) derived from gut bacteria are associated with protective roles in diseases ranging from obesity to colorectal cancers. Intake of microbially accessible dietary fibers (prebiotics) lead to varying effects on SCFA production in human studies, and gut microbial responses to nutritional interventions vary by individual. It is therefore possible that prebiotic therapies will require customizing to individuals.

RESULTS

Here, we explored prebiotic personalization by conducting a three-way crossover study of three prebiotic treatments in healthy adults. We found that within individuals, metabolic responses were correlated across the three prebiotics. Individual identity, rather than prebiotic choice, was also the major determinant of SCFA response. Across individuals, prebiotic response was inversely related to basal fecal SCFA concentration, which, in turn, was associated with habitual fiber intake. Experimental measures of gut microbial SCFA production for each participant also negatively correlated with fiber consumption, supporting a model in which individuals' gut microbiota are limited in their overall capacity to produce fecal SCFAs from fiber.

CONCLUSIONS

Our findings support developing personalized prebiotic regimens that focus on selecting individuals who stand to benefit, and that such individuals are likely to be deficient in fiber intake. Video Abstract.

Bioactive polysaccharides and oligosaccharides from garlic (Allium sativum L.): Production, physicochemical and biological properties, and structure-function relationships

Garlic is a common food, and many of its biological functions are attributed to its components including functional carbohydrates. Garlic polysaccharides and oligosaccharides as main components are understudied but have future value due to the growing demand for bioactive polysaccharides/oligosaccharides from natural sources. Garlic polysaccharides have molecular weights of 1 × 10³ to 2 × 10⁶  Da, containing small amounts of pectins and fructooligosaccharides and large amounts of inulin-type fructans ((2→1)-linked β-d-Fruf backbones alone or with attached (2→6)-linked β-d-Fruf branched chains). This article provides a detailed review of research progress and identifies knowledge gaps in extraction, production, composition, molecular characteristics, structural features, physicochemical properties, bioactivities, and structure-function relationships of garlic polysaccharides/oligosaccharides. Whether the extraction processes, synthesis approaches, and modification methods established for other non-garlic polysaccharides are also effective for garlic polysaccharides/oligosaccharides (to preserve their desired molecular structures and bioactivities) requires verification. The metabolic processes of ingested garlic polysaccharides/oligosaccharides (as food ingredients/dietary supplements), their modes of action in healthy humans or populations with chronic conditions, and molecular/chain organization-bioactivity relationships remain unclear. Future research directions related to garlic polysaccharides/oligosaccharides are discussed.

Effects of Dietary Fibers on Short-Chain Fatty Acids and Gut Microbiota Composition in Healthy Adults: A Systematic Review

There is an increasing interest in investigating dietary strategies able to modulate the gut microbial ecosystem which, in turn, may play a key role in human health. Dietary fibers (DFs) are widely recognized as molecules with prebiotic effects. The main objective of this systematic review was to: (i) analyze the results available on the impact of DF intervention on short chain fatty acids (SCFAs) production; (ii) evaluate the interplay between the type of DF intervention, the gut microbiota composition and its metabolic activities, and any other health associated outcome evaluated in the host. To this aim, initially, a comprehensive database of literature on human intervention studies assessing the effect of confirmed and candidate prebiotics on the microbial ecosystem was developed. Subsequently, studies performed on DFs and analyzing at least the impact on SCFA levels were extracted from the database. A total of 44 studies from 42 manuscripts were selected for the analysis. Among the different types of fiber, inulin was the DF investigated the most (n = 11). Regarding the results obtained on the ability of fiber to modulate total SCFAs, seven studies reported a significant increase, while no significant changes were reported in five studies, depending on the analytical methodology used. A total of 26 studies did not show significant differences in individual SCFAs, while the others reported significant differences for one or more SCFAs. The effect of DF interventions on the SCFA profile seemed to be strictly dependent on the dose and the type and structure of DFs. Overall, these results underline that, although affecting microbiota composition and derived metabolites, DFs do not produce univocal significant increase in SCFA levels in apparently healthy adults. In this regard, several factors (i.e., related to the study protocols and analytical methods) have been identified that could have affected the results obtained in the studies evaluated. Future studies are needed to better elucidate the relationship between DFs and gut microbiota in terms of SCFA production and impact on health-related markers.

The Effects of Prebiotics, Synbiotics, and Short-Chain Fatty Acids on Respiratory Tract Infections and Immune Function: A Systematic Review and Meta-Analysis

Prebiotics, synbiotics, and SCFAs have been shown to decrease systemic inflammation and play a protective role in chronic respiratory conditions. However, their effects on infection and immune function are unclear. The objective of this systematic review was to summarize the current evidence for prebiotic, synbiotic, and SCFA supplementation on respiratory tract infections (RTIs) and immune function. The protocol for this systematic review was registered with PROSPERO (National Institute for Health Research, University of York, UK), accessed online at https://www.crd.york.ac.uk/prospero (CRD42019118786). Relevant English-language articles up to May 2021 were identified via online databases: MEDLINE, EMBASE, CINAHL, and Cochrane Library. Included studies (n = 58) examined the effect of prebiotics, synbiotics, or SCFA, delivered orally, on the incidence, severity, or duration of RTIs and/or markers of immune function (e.g., peripheral blood immunophenotyping, NK cell activity). The majority of studies were randomized controlled trials reporting on RTIs in infants and children. The meta-analysis indicated that the numbers of subjects with ≥1 RTI were reduced with prebiotic (OR, 0.73; 95% CI: 0.62-0.86; P = 0.0002; n = 17) and synbiotic (OR, 0.75; 95% CI: 0.65-0.87; P = 0.0001; n = 9) supplementation compared to placebo. Further, NK cell activity was increased with synbiotic (standardized mean difference, 0.74; 95% CI: 0.42-1.06; P < 0.0001, n = 3) supplementation. This review provides evidence that prebiotic, specifically oligosaccharide, supplementation may play a protective role in RTIs in infants and children. There is less evidence for this effect in adults. Supplementation with prebiotic and synbiotic treatment may alter immune function by increasing NK cell activity, though effects on immunophenotype were less clear.

Fructooligosaccharides on inflammation, immunomodulation, oxidative stress, and gut immune response: a systematic review

CONTEXT

Evidence shows that fructooligosaccharides (FOSs) can modulate inflammatory, oxidative, and immune activity in the gut, possibly leading to a systemic response, improving human health.

OBJECTIVE

To assess the present knowledge of the effects of FOSs on inflammation, immunomodulation, oxidative stress, and gut immune response.

DATA SOURCES

Studies published between December 2000 and January 2020 were systematically searched in four databases: MEDLINE, LILACS, Web of Science, and Scopus. After the screening of 1316 articles, 8 human studies and 20 animal models were included.

DATA EXTRACTION

Data were extracted separately by 2 reviewers. For each study, the design, population, exposures, main results, and conclusion were extracted. The research questions and the risk-of-bias information were also extracted. Additionally, the risk-of-bias were analyzed to guarantee the reliability of this review.

DATA ANALYSIS

A qualitative analysis revealed that FOSs can increase bifidobacteria counts and short-chain fatty acids in the gut, stimulate IgA secretion in the colon, and decrease proinflammatory cytokines, thus influencing metabolic diseases.

CONCLUSION

Studies suggest that FOS supplementation is positively associated with an anti-inflammatory and antioxidant effect, thus enhancing the gut immune system, which may be beneficial for the host's health.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration nos 42020209865 and 42020220369.

The Prebiotic Potential of Inulin-type Fructans: A Systematic Review

Inulin-type fructans (ITF), including short-chain fructooligosaccharides (scFOS), oligofructose, and inulin, are commonly used fibers that are widely regarded as prebiotic for their ability to be selectively utilized by the intestinal microbiota to confer a health benefit. However, the literature thus far lacks a thorough discussion of the evidence from human clinical trials for the prebiotic effect of ITF, including both effects on the intestinal microbiota composition as well as the intestinal and extraintestinal (e.g., glucose homeostasis, lipids, mineral absorption and bone health, appetite and satiety, inflammation and immune function, and body composition) benefits. Additionally, there is a lack of discussion regarding aspects such as the effect of ITF chain length on its intestinal and extraintestinal effects. The overall objective of this systematic review was to summarize the prebiotic potential of ITF based on the results of human clinical trials in healthy adult populations. Evidence from studies included in the current review suggest that ITF have a prebiotic effect on the intestinal microbiota, promoting the abundances of Bifidobacterium, Lactobacillus, and Faecalibacterium prausnitzii. Beneficial health effects reported following ITF intake include improved intestinal barrier function, improved laxation, increased insulin sensitivity, decreased triglycerides and an improved lipid profile, increased absorption of calcium and magnesium, and increased satiety. While there is some evidence for differing effects of ITF based on chain length, lack of direct comparisons and detailed descriptions of physicochemical properties limit the ability to draw conclusions from human clinical studies. Future research should focus on elucidating the mechanisms by which the intestinal microbiota mediates or modifies the effects of ITF on human health and the contribution of individual factors such as age and metabolic health to move towards personalization of prebiotic application.

Effect of supplemental prebiotics, probiotics and bioactive proteins on the microbiome composition and fecal calprotectin in C57BL6/j mice

The composition and metabolic activity of the microbiome affect many aspects of health, and there is current interest in dietary constituents that may affect this system. The purpose of this study was to evaluate the effects of a mix of probiotics, a mix of prebiotics and a bioactive protein fraction on the microbiome, when fed to mice alone and in combination at physiologically relevant doses. Mice were fed the total western diet (TWD) supplemented with prebiotics, probiotics, and bioactive proteins individually and in combination for four weeks. Subsequently, effects on the composition of the gut microbiome, gut short-chain fatty acids (SCFAs) concentration, and gut inflammation were measured. Ruminococcus gnavus was increased in mice gut microbiome after feeding prebiotics. Bifidobacterium longum was increased after feeding probiotics. The treatments significantly affected beta-diversity with minor treatment effects on cecal or fecal SCFAs levels, and the treatments did not affect gut inflammation as measured by fecal calprotectin.

Potential Impacts of Prebiotics and Probiotics in Cancer Prevention

BACKGROUND

Cancer is a serious problem throughout the world. The pathophysiology of cancer is multifactorial and is also related to gut microbiota. Intestinal microbes are the useful resident of the healthy human. They play various aspects of human health including nutritional biotransformation, flushing of the pathogens, toxin neutralization, immune response, and onco-suppression. Disruption in the interactions among the gut microbiota, intestinal epithelium, and the host immune system are associated with gastrointestinal disorders, neurodegenerative diseases, metabolic syndrome, and cancer. Probiotic bacteria (Lactobacillus spp., Bifidobacterium spp.) have been regarded as beneficial to health and shown to play a significant role in immunomodulation and displayed preventive role against obesity, diabetes, liver disease, inflammatory bowel disease, tumor progression, and cancer.

OBJECTIVE

The involvement of gut microorganisms in cancer development and prevention has been recognized as a balancing factor. The events of dysbiosis emphasize metabolic disorder and carcinogenesis. The gut flora potentiates immunomodulation and minimizes the limitations of usual chemotherapy. The significant role of prebiotics and probiotics on the improvement of immunomodulation and antitumor properties has been considered.

METHODS

I had reviewed the literature on the multidimensional activities of prebiotics and probiotics from the NCBI website database PubMed, Springer Nature, Science Direct (Elsevier), Google Scholar database to search relevant articles. Specifically, I had focused on the role of prebiotics and probiotics in immunomodulation and cancer prevention.

RESULTS

Prebiotics are the nondigestible fermentable sugars that selectively influence the growth of probiotic organisms that exert immunomodulation over the cancerous growth. The oncostatic properties of bacteria are mediated through the recruitment of cytotoxic T cells, natural killer cells, and oxidative stress-induced apoptosis in the tumor microenvironment. Moreover, approaches have also been taken to use probiotics as an adjuvant in cancer therapy.

CONCLUSION

The present review has indicated that dysbiosis is the crucial factor in many pathological situations including cancer. Applications of prebiotics and probiotics exhibit the immune-surveillance as oncostatic effects. These events increase the possibilities of new therapeutic strategies for cancer prevention.

Therapeutic potential of natural products against atherosclerosis: Targeting on gut microbiota

Gut microbiota (GM) has emerged as an essential and integral factor for maintaining human health and affecting pathological outcomes. Metagenomics and metabolomics characterization have furthered gut metagenome's understanding and unveiled that deviation of specific GM community members and GM-dependent metabolites imbalance orchestrate metabolic or cardiovascular diseases (CVDs). Restoring GM ecosystem with nutraceutical supplements keenly prebiotics and probiotics relatively decreases CVDs incidence and overall mortality. In Atherosclerosis, commensal and pathogenic gut microbes correlate with atherogenesis events. GM-dependent metabolites-trimethylamine N-oxide and short-chain fatty acids regulate atherosclerosis-related metabolic processes in opposite patterns to affect atherosclerosis outcomes. Therefore, GM might be a potential therapeutic target for atherosclerosis. In atherogenic animal models, natural products with cardioprotective properties could modulate the GM ecosystem by revitalizing healthier GM phylotypes and abrogating proatherogenic metabolites, paving future research paths for clinical therapeutics.

Effects of High-Fat Diet Induced Obesity and Fructooligosaccharide Supplementation on Cardiac Protein Expression

The mechanism by which high fat-diet induced obesity affects cardiac protein expression is unclear, and the extent to which this is modulated by prebiotic treatment is not known. These outcomes were assessed in rats initially fed a high-fat diet, then the top 40% weight gain group were randomly allocated to control (CON), high-fat (HF) and HF supplemented with fructooligosaccharide (32 g; HF-FOS) treatments for 12 weeks (n = 10/group). At sacrifice, left ventricles were either frozen or preserved in formalin. Serum was stored for glucose and insulin measurements. Protein spectra was obtained using an Orbitrap analyzer, processed with Sequest and fold changes assessed with Scaffold Q +. Treatment effects for body weights, glucose and insulin were assessed using one-way ANOVA, and the differential protein expression was assessed by a Mann-Whitney U test. The Database for Annotation, Visualization and Integrated Discovery and the Kyoto Encyclopedia of Genes and Genomes identified pathways containing overrepresented proteins. Hematoxylin and eosin sections were graded for hypertrophy and also quantified; differences were identified using Chi-square analyses and Mann-Whitney U tests. HF diet fed rats were significantly (p < 0.05) heavier than CON, and 23 proteins involved in mitochondrial function and lipid metabolism were differentially expressed between HF and CON. Between HF-FOS and HF, 117 proteins involved in contractility, lipid and carbohydrate metabolism were differentially expressed. HF cardiomyocytes were significantly (p < 0.05) more hypertrophic than CON. We conclude that high-fat feeding and FOS are associated with subcellular deviations in cardiac metabolism and contractility, which may influence myocardial function and alter the risk of cardiovascular disease.

Impact of prebiotics on immune response: from the bench to the clinic

Several preclinical and clinical studies have shown the immunomodulatory role exerted by prebiotics in regulating the immune response. In this review, we describe the mechanistic and clinical studies that decipher the cell signaling pathways implicated in the process. Prebiotic fibers are conventionally known to serve as substrate for probiotic commensal bacteria that release of short-chain fatty acids in the intestinal tract along with several other metabolites. Subsequently, they then act on the local as well as the systemic immune cells and the gut-associated epithelial cells, primarily through G-protein-coupled receptor-mediated pathways. However, other pathways including histone deacetylase inhibition and inflammasome pathway have also been implicated in regulating the immunomodulatory effect. The prebiotics can also induce a microbiota-independent effect by directly acting on the gut-associated epithelial and innate immune cells through the Toll-like receptors. The cumulative effect results in the maintenance of the epithelial barrier integrity and modulation of innate immunity through secretion of pro- and anti-inflammatory cytokines, switches in macrophage polarization and function, neutrophil recruitment and migration, dendritic cell and regulatory T-cell differentiation. Extending these in vitro and ex vivo observations, some prebiotics have been well investigated, with successful human and animal trials demonstrating the association between gut microbes and immunity biomarkers leading to improvement in health endpoints across populations. This review discusses scientific insights into the association between prebiotics, innate immunity and gut microbiome from in vitro to human oral intervention.

How strong is the evidence that gut microbiota composition can be influenced by lifestyle interventions in a cardio-protective way?

Alterations in composition and function of the gut microbiota have been demonstrated in diseases involving the cardiovascular system, particularly coronary heart disease and atherosclerosis. The data are still limited but the typical altered genera include Roseburia and Faecalibacterium. Plausible mechanisms by which microbiota may mediate cardio-protective effects have been postulated, including the production of metabolites like trimethylamine (TMA), as well as immunomodulatory functions. This raises the question of whether it is possible to modify the gut microbiota by lifestyle interventions and thereby improve cardiovascular health. Nevertheless, lifestyle intervention studies that have involved modifications of dietary intake and/or physical activity, as well as investigating changes in the gut microbiota and subsequent modifications of the cardioprotective markers, are still scarce, and the results have been inconclusive. Current evidence points to benefits of consuming high-fibre foods, nuts and an overall healthy dietary pattern to achieve beneficial effects on both gut microbiota and serum cardiovascular markers, primarily lipids. The relationship between physical exercise and gut microbiota is probably complex and may be dependent on the intensity of exercise. In this article, we review the available evidence on lifestyle, specifically diet, physical activity and smoking as modifiers of the gut microbiota, and subsequently as modifiers of serum cardiovascular health markers. We have attempted to elucidate the plausible mechanisms and further critically appraise the caveats and gaps in the research.

Microbiota and Lifestyle: A Special Focus on Diet

It is widely known that a good balance and healthy function for bacteria groups in the colon are necessary to maintain homeostasis and preserve health. However, the lack of consensus on what defines a healthy gut microbiota and the multitude of factors that influence human gut microbiota composition complicate the development of appropriate dietary recommendations for our gut microbiota. Furthermore, the varied response to the intake of probiotics and prebiotics observed in healthy adults suggests the existence of potential inter- and intra-individual factors, which might account for gut microbiota changes to a greater extent than diet. The changing dietary habits worldwide involving consumption of processed foods containing artificial ingredients, such as sweeteners; the coincident rise in emotional disorders; and the worsening of other lifestyle habits, such as smoking habits, drug consumption, and sleep, can together contribute to gut dysbiosis and health impairment, as well as the development of chronic diseases. This review summarizes the current literature on the effects of specific dietary ingredients (probiotics, prebiotics, alcohol, refined sugars and sweeteners, fats) in the gut microbiota of healthy adults and the potential inter- and intra-individual factors involved, as well as the influence of other potential lifestyle factors that are dramatically increasing nowadays.

The role of short-chain fatty acids in microbiota-gut-brain communication

Short-chain fatty acids (SCFAs), the main metabolites produced by bacterial fermentation of dietary fibre in the gastrointestinal tract, are speculated to have a key role in microbiota-gut-brain crosstalk. However, the pathways through which SCFAs might influence psychological functioning, including affective and cognitive processes and their neural basis, have not been fully elucidated. Furthermore, research directly exploring the role of SCFAs as potential mediators of the effects of microbiota-targeted interventions on affective and cognitive functioning is sparse, especially in humans. This Review summarizes existing knowledge on the potential of SCFAs to directly or indirectly mediate microbiota-gut-brain interactions. The effects of SCFAs on cellular systems and their interaction with gut-brain signalling pathways including immune, endocrine, neural and humoral routes are described. The effects of microbiota-targeted interventions such as prebiotics, probiotics and diet on psychological functioning and the putative mediating role of SCFA signalling will also be discussed, as well as the relationship between SCFAs and psychobiological processes. Finally, future directions to facilitate direct investigation of the effect of SCFAs on psychological functioning are outlined.

Effect of Pereskia aculeata Mill. in vitro and in overweight humans: A randomized controlled trial

OBJECTIVES

The objective of this study was to investigate the influence of ora-pro-nobis (Pereskia aculeata Mill.) flour on the adhesion of probiotics to intestinal epithelial cells and to evaluate the effect of a product based on this flour on gastrointestinal symptoms, weight, body fat, glycemia, and lipid profile in overweight men.

METHODS

Microbiological counts (probiotic count, survival after in vitro gastrointestinal resistance, Caco-2 cell adhesion) were analyzed. A randomized, cross-over intervention was performed. Intestinal microbiota was indirectly assessed on the basis of consistency, color of feces, and gastrointestinal symptoms.

RESULTS

P. aculeata did not affect Lactobacillus casei adhesion to Caco-2 cells. Ora-pro-nobis flour improved gastrointestinal symptoms and increased satiety.

CONCLUSION

The consumption of ora-pro-nobis flour improved intestinal health. In addition, it maintained the high adherence of L. casei to intestinal cells as well as patient anthropometric and biochemical parameters.

PRACTICAL APPLICATIONS

Pereskia aculeata Mill. is well known in folk medicine and has several nutrients; however, there are few studies on this plant. This is the first study to analyze the influence of P. aculeata on bacterial adherence and the first cross-over clinical trial to evaluate the beneficial potential of ora-pro-nobis flour in overweight men. Thus, this study will contribute to the promotion of ora-pro-nobis as a functional ingredient and will arouse the interest of industries to develop related healthy foods. In addition, it is an effective dietary strategy to improve the gastrointestinal health of men.

The role of diet and intestinal microbiota in the development of metabolic syndrome

Metabolic syndrome (MetS) is a cluster of metabolic factors that increase the risk of cardiovascular disease and type 2 diabetes mellitus (T2DM), which is in itself a major cardiovascular disease risk factor. The aim of this review is to summarize the data related to the influence of the gut microbiota on the development of obesity and the MetS, highlighting the role of diet in controlling the MetS by modifying the gut microbiota. The main alterations in the gut microbiota of individuals with MetS consist of an increased Firmicutes/Bacteriodetes ratio and a reduced capacity to degrade carbohydrates to short-chain fatty acids, which in turn is related with the metabolic dysfunction of the host organism rather than with obesity itself. In addition to a low-fat, high-carbohydrate diet, with its high fiber intake, a diet with 30% fat content but with a high content in fruit and vegetables, such as the Mediterranean diet, is beneficial and partially restores the dysbiosis found in individuals with MetS. Overall, the shaping of the gut microbiota through the administration of prebiotics or probiotics increases the short-chain fatty acid production and is therefore a valid alternative in MetS treatment.

Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications

Prebiotics are a group of nutrients that are degraded by gut microbiota. Their relationship with human overall health has been an area of increasing interest in recent years. They can feed the intestinal microbiota, and their degradation products are short-chain fatty acids that are released into blood circulation, consequently, affecting not only the gastrointestinal tracts but also other distant organs. Fructo-oligosaccharides and galacto-oligosaccharides are the two important groups of prebiotics with beneficial effects on human health. Since low quantities of fructo-oligosaccharides and galacto-oligosaccharides naturally exist in foods, scientists are attempting to produce prebiotics on an industrial scale. Considering the health benefits of prebiotics and their safety, as well as their production and storage advantages compared to probiotics, they seem to be fascinating candidates for promoting human health condition as a replacement or in association with probiotics. This review discusses different aspects of prebiotics, including their crucial role in human well-being.

Effects of β-Fructans Fiber on Bowel Function: A Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was to assess the effects of β-fructan supplementation on bowel function in healthy volunteers and patients. The search process was based on the selection of publications listed in the Pubmed and EUPMC database until December 2017, plus two unpublished studies, to identify studies evaluating the impact of β-fructans on bowel movement and stool parameters. Forty-seven publications were selected for inclusion. Primary parameter was frequency of bowel movements, evaluated by the number of defecations per day during the study period. Secondary outcomes were stool consistency, stool dry and wet weights, and transit time. Short-chain (DP < 10) β-fructans contributed to increased stool frequency (0.36 defecation +/- 0.06 per day; p < 0.001), while no significant effect was reported with long-chain (DP ≥ 10) β-fructans (-0.03 +/- 0.11, p = 0.82). A minimal increase in stool wet weight was also statistically demonstrated with short-chain β-fructans. Moreover, the meta-analysis highlighted significant differences in stool consistency in contrast to fecal dry weight after β-fructan supplementation. This systematic review and meta-analysis indicates that short-chain β-fructan supplementation has a positive effect on bowel function by significantly increasing the frequency of bowel movements.

Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis

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.

Impact of β2-1 fructan on faecal community change: results from a placebo-controlled, randomised, double-blinded, cross-over study in healthy adults

Healthy adults (n 30) participated in a placebo-controlled, randomised, double-blinded, cross-over study consisting of two 28 d treatments (β2-1 fructan or maltodextrin; 3×5 g/d) separated by a 14-d washout. Subjects provided 1 d faecal collections at days 0 and 28 of each treatment. The ability of faecal bacteria to metabolise β2-1 fructan was common; eighty-seven species (thirty genera, and four phyla) were isolated using anaerobic medium containing β2-1 fructan as the sole carbohydrate source. β2-1 fructan altered the faecal community as determined through analysis of terminal restriction fragment length polymorphisms and 16S rRNA genes. Supplementation with β2-1 fructan reduced faecal community richness, and two patterns of community change were observed. In most subjects, β2-1 fructan reduced the content of phylotypes aligning within the Bacteroides, whereas increasing those aligning within bifidobacteria, Faecalibacterium and the family Lachnospiraceae. In the remaining subjects, supplementation increased the abundance of Bacteroidetes and to a lesser extent bifidobacteria, accompanied by decreases within the Faecalibacterium and family Lachnospiraceae. β2-1 Fructan had no impact on the metagenome or glycoside hydrolase profiles in faeces from four subjects. Few relationships were found between the faecal bacterial community and various host parameters; Bacteroidetes content correlated with faecal propionate, subjects whose faecal community contained higher Bacteroidetes produced more caproic acid independent of treatment, and subjects having lower faecal Bacteroidetes exhibited increased concentrations of serum lipopolysaccharide and lipopolysaccharide binding protein independent of treatment. We found no evidence to support a defined health benefit for the use of β2-1 fructans in healthy subjects.

Modulation of the Gastrointestinal Microbiome with Nondigestible Fermentable Carbohydrates To Improve Human Health

There is a clear association between the gastrointestinal (GI) microbiome and the development of chronic noncommunicable diseases, providing a rationale for the development of strategies that target the GI microbiota to improve human health. In this article, we discuss the potential of supplementing the human diet with nondigestible fermentable carbohydrates (NDFCs) to modulate the composition, structure, diversity, and metabolic potential of the GI microbiome in an attempt to prevent or treat human disease. The current concepts by which NDFCs can be administered to humans, including prebiotics, fermentable dietary fibers, and microbiota-accessible carbohydrates, as well as the mechanisms by which these carbohydrates exert their health benefits, are discussed. Epidemiological research presents compelling evidence for the health effects of NDFCs, with clinical studies providing further support for some of these benefits. However, rigorously designed human intervention studies with well-established clinical markers and microbial endpoints are still essential to establish (i) the clinical efficiency of specific NDFCs, (ii) the causal role of the GI microbiota in these effects, (iii) the underlying mechanisms involved, and (iv) the degree by which inter-individual differences between GI microbiomes influence these effects. Such studies would provide the mechanistic understanding needed for a systematic application of NDFCs to improve human health via GI microbiota modulation while also allowing the personalization of these dietary strategies.

Short-chain fatty acids, prebiotics, synbiotics, and systemic inflammation: a systematic review and meta-analysis

BACKGROUND

Prebiotic soluble fibers are fermented by beneficial bacteria in the colon to produce short-chain fatty acids (SCFAs), which are proposed to have systemic anti-inflammatory effects.

OBJECTIVE

This review examines the effect of SCFAs, prebiotics, and pre- and probiotic combinations (synbiotics) on systemic inflammation.

DESIGN

Relevant English language studies from 1947 to May 2017 were identified with the use of online databases. Studies were considered eligible if they examined the effects of SCFAs, prebiotics, or synbiotics; were delivered orally, intravenously, or per rectum; were on biomarkers of systemic inflammation in humans; and performed meta-analysis where possible.

RESULTS

Sixty-eight studies were included. Fourteen of 29 prebiotic studies and 13 of 26 synbiotic studies reported a significant decrease in ≥1 marker of systemic inflammation. Eight studies compared prebiotic and synbiotic supplementation, 2 of which reported a decrease in inflammation with synbiotics only, with 1 reporting a greater anti-inflammatory effect with synbiotics than with prebiotics alone. Meta-analyses indicated that prebiotics reduce C-reactive protein (CRP) [standardized mean difference (SMD): -0.60; 95% CI: -0.98, -0.23], and synbiotics reduce CRP (SMD: -0.40; 95% CI: -0.73, -0.06) and tumor necrosis factor-α (SMD -0.90; 95% CI: -1.50, -0.30).

CONCLUSIONS

There is significant heterogeneity of outcomes in studies examining the effect of prebiotics and synbiotics on systemic inflammation. Approximately 50% of included studies reported a decrease in ≥1 inflammatory biomarker. The inconsistency in reported outcomes may be due to heterogeneity in study design, supplement formulation, dosage, duration, and subject population. Nonetheless, meta-analyses provide evidence to support the systemic anti-inflammatory effects of prebiotic and synbiotic supplementation.

Significance of Microbiota in Obesity and Metabolic Diseases and the Modulatory Potential by Medicinal Plant and Food Ingredients

Metabolic syndrome is a cluster of three or more metabolic disorders including insulin resistance, obesity, and hyperlipidemia. Obesity has become the epidemic of the twenty-first century with more than 1.6 billion overweight adults. Due to the strong connection between obesity and type 2 diabetes, obesity has received wide attention with subsequent coining of the term "diabesity." Recent studies have identified unique contributions of the immensely diverse gut microbiota in the pathogenesis of obesity and diabetes. Several mechanisms have been proposed including altered glucose and fatty acid metabolism, hepatic fatty acid storage, and modulation of glucagon-like peptide (GLP)-1. Importantly, the relationship between unhealthy diet and a modified gut microbiota composition observed in diabetic or obese subjects has been recognized. Similarly, the role of diet rich in polyphenols and plant polysaccharides in modulating gut bacteria and its impact on diabetes and obesity have been the subject of investigation by several research groups. Gut microbiota are also responsible for the extensive metabolism of polyphenols thus modulating their biological activities. The aim of this review is to shed light on the composition of gut microbes, their health importance and how they can contribute to diseases as well as their modulation by polyphenols and polysaccharides to control obesity and diabetes. In addition, the role of microbiota in improving the oral bioavailability of polyphenols and hence in shaping their antidiabetic and antiobesity activities will be discussed.

The challenges of control groups, placebos and blinding in clinical trials of dietary interventions

High-quality placebo-controlled evidence for food, nutrient or dietary advice interventions is vital for verifying the role of diet in optimising health or for the management of disease. This could be argued to be especially important where the benefits of dietary intervention are coupled with potential risks such as compromising nutrient intake, particularly in the case of exclusion diets. The objective of the present paper is to explore the challenges associated with clinical trials in dietary research, review the types of controls used and present the advantages and disadvantages of each, including issues regarding placebos and blinding. Placebo-controlled trials in nutrient interventions are relatively straightforward, as in general placebos can be easily produced. However, the challenges associated with conducting placebo-controlled food interventions and dietary advice interventions are protean, and this has led to a paucity of placebo-controlled food and dietary advice trials compared with drug trials. This review appraises the types of controls used in dietary intervention trials and provides recommendations and nine essential criteria for the design and development of sham diets for use in studies evaluating the effect of dietary advice, along with practical guidance regarding their evaluation. The rationale for these criteria predominantly relate to avoiding altering the outcome of interest in those delivered the sham intervention in these types of studies, while not compromising blinding.

Effects of varying dietary content of fermentable short-chain carbohydrates on symptoms, fecal microenvironment, and cytokine profiles in patients with irritable bowel syndrome

BACKGROUND

A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) is increasingly recommended for patients with irritable bowel syndrome (IBS). We aimed to investigate the effects of a blinded low-FODMAP vs high-fructo-oligosaccharides (FOS) diet on symptoms, immune activation, gut microbiota composition, and short-chain fatty acids (SCFAs).

METHODS

Twenty patients with diarrhea-predominant or mixed IBS were instructed to follow a low-FODMAP diet (LFD) throughout a 9-week study period. After 3 weeks, they were randomized and double-blindly assigned to receive a supplement of either FOS (FODMAP) or maltodextrin (placebo) for the next 10 days, followed by a 3-week washout period before crossover. Irritable bowel syndrome severity scoring system (IBS-SSS) was used to evaluate symptoms. Cytokines (interleukin [IL]-6, IL-8, and tumor necrosis factor alpha) were analyzed in blood samples, and gut microbiota composition (16S rRNA) and SCFAs were analyzed in fecal samples.

KEY RESULTS

Irritable bowel syndrome symptoms consistently improved after 3 weeks of LFD, and significantly more participants reported symptom relief in response to placebo (80%) than FOS (30%). Serum levels of proinflammatory IL-6 and IL-8, as well as levels of fecal bacteria (Actinobacteria, Bifidobacterium, and Faecalibacterium prausnitzii), total SCFAs, and n-butyric acid, decreased significantly on the LFD as compared to baseline. Ten days of FOS supplementation increased the level of these bacteria, whereas levels of cytokines and SCFAs remained unchanged.

CONCLUSIONS AND INFERENCES

Our findings support the efficacy of a LFD in alleviating IBS symptoms, and show changes in inflammatory cytokines, microbiota profile, and SCFAs, which may have consequences for gut health.

Infant food applications of complex carbohydrates: Structure, synthesis, and function

Professional health bodies such as the World Health Organization (WHO), the American Academy of Pediatrics (AAP), and the U.S. Department of Health and Human Services (HHS) recommend breast milk as the sole source of food during the first year of life. This position recognizes human milk as being uniquely suited for infant nutrition. Nonetheless, most neonates in the West are fed alternatives by 6 months of age. Although inferior to human milk in most aspects, infant formulas are able to promote effective growth and development. However, while breast-fed infants feature a microbiota dominated by bifidobacteria, the bacterial flora of formula-fed infants is usually heterogeneous with comparatively lower levels of bifidobacteria. Thus, the objective of any infant food manufacturer is to prepare a product that results in a formula-fed infant developing a breast-fed infant-like microbiota. The goal of this focused review is to discuss the structure, synthesis, and function of carbohydrate additives that play a role in governing the composition of the infant microbiome and have other health benefits.

Distant Site Effects of Ingested Prebiotics

The gut microbiome is being more widely recognized for its association with positive health outcomes, including those distant to the gastrointestinal system. This has given the ability to maintain and restore microbial homeostasis a new significance. Prebiotic compounds are appealing for this purpose as they are generally food-grade substances only degraded by microbes, such as bifidobacteria and lactobacilli, from which beneficial short-chain fatty acids are produced. Saccharides such as inulin and other fructo-oligosaccharides, galactooligosaccharides, and polydextrose have been widely used to improve gastrointestinal outcomes, but they appear to also influence distant sites. This review examined the effects of prebiotics on bone strength, neural and cognitive processes, immune functioning, skin, and serum lipid profile. The mode of action is in part affected by intestinal permeability and by fermentation products reaching target cells. As the types of prebiotics available diversify, so too will our understanding of the range of microbes able to degrade them, and the extent to which body sites can be impacted by their consumption.