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The Effects of Vegetarian and Vegan Diets on Gut Microbiota.
Tomova, A, Bukovsky, I, Rembert, E, Yonas, W, Alwarith, J, Barnard, ND, Kahleova, H
Frontiers in nutrition. 2019;6:47
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The difference in gut microbiota composition between individuals following vegan or vegetarian diets and those following omnivorous diets is well documented. A plant-based diet appears to be beneficial for human health by promoting the development of more diverse and stable microbial systems. This diversity appears to have an important association with BMI, obesity, and arterial compliance. This review highlights the effects of different diets, particularly plant-based diets, on the gut microbiota composition and production of microbial metabolites affecting the host health. The ratio between Bacteroidetes and Firmicutes is discussed and how different diets can change it. It explains how diet can affect the three main enterotypes: Prevotella, Bacteroides, and Ruminococcus. The food components proteins, carbohydrates, fats and polyphenols are discussed and how they influence gut microbiota. Up to date knowledge suggests that a plant-based diet may be an effective way to promote a diverse ecosystem of beneficial microbes that support overall health. However, due to the complexity and inter-individual differences, further research is required to fully characterize the interactions between diet, the microbiome, and health outcomes.
Abstract
The difference in gut microbiota composition between individuals following vegan or vegetarian diets and those following omnivorous diets is well documented. A plant-based diet appears to be beneficial for human health by promoting the development of more diverse and stable microbial systems. Additionally, vegans and vegetarians have significantly higher counts of certain Bacteroidetes-related operational taxonomic units compared to omnivores. Fibers (that is, non-digestible carbohydrates, found exclusively in plants) most consistently increase lactic acid bacteria, such as Ruminococcus, E. rectale, and Roseburia, and reduce Clostridium and Enterococcus species. Polyphenols, also abundant in plant foods, increase Bifidobacterium and Lactobacillus, which provide anti-pathogenic and anti-inflammatory effects and cardiovascular protection. High fiber intake also encourages the growth of species that ferment fiber into metabolites as short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate. The positive health effects of SCFAs are myriad, including improved immunity against pathogens, blood-brain barrier integrity, provision of energy substrates, and regulation of critical functions of the intestine. In conclusion, the available literature suggests that a vegetarian/vegan diet is effective in promoting a diverse ecosystem of beneficial bacteria to support both human gut microbiome and overall health. This review will focus on effects of different diets and nutrient contents, particularly plant-based diets, on the gut microbiota composition and production of microbial metabolites affecting the host health.
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Fermented Foods: Definitions and Characteristics, Impact on the Gut Microbiota and Effects on Gastrointestinal Health and Disease.
Dimidi, E, Cox, SR, Rossi, M, Whelan, K
Nutrients. 2019;11(8)
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Fermented foods have grown in popularity due to their proposed health benefits but there is limited clinical evidence for the effectiveness of most fermented foods in gastrointestinal health. This review paper looks at non-dairy fermented foods which have been studied in at least one RCT: kefir, sauerkraut, natto, and sourdough bread. The health benefits are attributed to the high ratio of probiotic microorganisms, metabolites, or ability to convert compounds into active metabolites, as well as prebiotics and vitamins contained in these foods. Kimchi has the greatest evidence from epidemiological and case control studies investigating risk of gastric cancers. Different food composition of kimchi is shown to both increase and decrease risks, whilst it had no impact on H. pylori levels. There were no studies on kefir in functional bowel disorders however, it was shown to help lactose malabsorption and reduce H. pylori levels. A small RCT on Sauerkraut showed it reduced IBS severity in patients and increased in vitro activity of key liver and kidney detoxifying enzymes. There are small pockets of data that show that tempeh may influence gut microbiota in humans, and that natto may increase bifidobacterial and short-chain fatty acids in healthy volunteers. There are numerous limited cohort studies on miso and cancer risk but no studies on gastrointestinal conditions. Finally, sourdough was shown to reduce FODMAPS and be better tolerated in IBS patients, reducing bloating, nausea and discomfort. Overall, all the studies provide insufficient evidence on fermented foods and gastrointestinal health.
Abstract
Fermented foods are defined as foods or beverages produced through controlled microbial growth, and the conversion of food components through enzymatic action. In recent years, fermented foods have undergone a surge in popularity, mainly due to their proposed health benefits. The aim of this review is to define and characterise common fermented foods (kefir, kombucha, sauerkraut, tempeh, natto, miso, kimchi, sourdough bread), their mechanisms of action (including impact on the microbiota), and the evidence for effects on gastrointestinal health and disease in humans. Putative mechanisms for the impact of fermented foods on health include the potential probiotic effect of their constituent microorganisms, the fermentation-derived production of bioactive peptides, biogenic amines, and conversion of phenolic compounds to biologically active compounds, as well as the reduction of anti-nutrients. Fermented foods that have been tested in at least one randomised controlled trial (RCT) for their gastrointestinal effects were kefir, sauerkraut, natto, and sourdough bread. Despite extensive in vitro studies, there are no RCTs investigating the impact of kombucha, miso, kimchi or tempeh in gastrointestinal health. The most widely investigated fermented food is kefir, with evidence from at least one RCT suggesting beneficial effects in both lactose malabsorption and Helicobacter pylori eradication. In summary, there is very limited clinical evidence for the effectiveness of most fermented foods in gastrointestinal health and disease. Given the convincing in vitro findings, clinical high-quality trials investigating the health benefits of fermented foods are warranted.
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Small Intestinal Bacterial Overgrowth in Children: A State-Of-The-Art Review.
Avelar Rodriguez, D, Ryan, PM, Toro Monjaraz, EM, Ramirez Mayans, JA, Quigley, EM
Frontiers in pediatrics. 2019;7:363
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Small intestinal bacterial overgrowth (SIBO) occurs when microorganisms overpopulate the small intestine and is characterised by gastrointestinal symptoms such as abdominal pain, diarrhoea, and flatulence. This review focuses on paediatric SIBO, known to be increasing, with emphasis on the impact on gut microbiota. The gut microbiota is influenced by several factors including genetics, vaginal delivery, exercise and diet. SIBO in children has been studied in the context of stunting, irritable bowel syndrome (IBS), obesity, and related to use of proton pump inhibitors (PPIs). This review analysed 149 studies published since 2000 through till May 2019 with the aim of presenting the most up-to-date information. Risk factors included gastric acids and medications which suppress this activity, intestinal motility disturbances leading to bacterial overgrowth, anatomical anomalies where there is an absence of one or more intestinal valves, and poor socioeconomic status and diet. The review concluded that the recommended diagnosis is by methane and hydrogen breath testing and that Gold Standard treatment is antibiotic ‘rifaximin’ at 1,200 mg/d, reduced to 600 mg/d for 1 week in children. Alternative treatments discussed include FODMAP diets and probiotic protocols with best results coming from combining antibiotic and probiotic protocols. It concludes that SIBO in children is heterogenous and poorly understood and that a better diagnostic criteria is necessary in paediatrics.
Abstract
Small intestinal bacterial overgrowth (SIBO) is a heterogenous and poorly understood entity characterised by an excessive growth of select microorganisms within the small intestine. This excessive bacterial biomass, in turn, disrupts host physiology in a myriad of ways, leading to gastrointestinal and non-gastrointestinal symptoms and complications. SIBO is a common cause of non-specific gastrointestinal symptoms in children, such as chronic abdominal pain, abdominal distention, diarrhoea, and flatulence, amongst others. In addition, it has recently been implicated in the pathophysiology of stunting, a disease that affects millions of children worldwide. Risk factors such as acid-suppressive therapies, alterations in gastrointestinal motility and anatomy, as well as impoverished conditions, have been shown to predispose children to SIBO. SIBO can be diagnosed via culture-dependant or culture-independent approaches. SIBO's epidemiology is limited due to the lack of uniformity and consensus of its diagnostic criteria, as well as the paucity of literature available. Antibiotics remain the first-line treatment option for SIBO, although emerging modalities such as probiotics and diet manipulation could also have a role. Herein, we present a state-of-the-art-review which aims to comprehensively outline the most current information on SIBO in children, with particular emphasis on the gut microbiota.
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Does the microbiome and virome contribute to myalgic encephalomyelitis/chronic fatigue syndrome?
Newberry, F, Hsieh, SY, Wileman, T, Carding, SR
Clinical science (London, England : 1979). 2018;132(5):523-542
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Myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) (ME/CFS) is a disabling and debilitating disease. Several studies have shown alterations in the gut microbiome (dysbiosis) in patients with ME/CFS. However, in focusing on the bacterial components of the microbiome, the viral component of the microbiome (known as the virome) has been neglected. Viruses can change the microbiome which can influence the health. This area is therefore important for research into ME/CFS. This article provides a comprehensive review of the current evidence supporting microbiome alterations in ME/CFS patients. Additionally, the challenges associated with microbiome studies are discussed. A literature search was done and 11 papers were found that had examined the microbiome ME/CFS patients, dating from 1998 to 2017. It was not possible to compare the studies statistically but from looking at each one individually there is sufficient evidence to support the claim of an altered intestinal microbiome in ME/CFS patients. ME/CFS is multifactorial and potential dysbiosis should be considered to be only part of the picture. Future studies are needed to adopt standardized techniques and analyses. As research increases, it is becoming clear that the virome can directly and indirectly affect host health, and may play a role in the pathogenesis of ME/CFS.
Abstract
Myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) (ME/CFS) is a disabling and debilitating disease of unknown aetiology. It is a heterogeneous disease characterized by various inflammatory, immune, viral, neurological and endocrine symptoms. Several microbiome studies have described alterations in the bacterial component of the microbiome (dysbiosis) consistent with a possible role in disease development. However, in focusing on the bacterial components of the microbiome, these studies have neglected the viral constituent known as the virome. Viruses, particularly those infecting bacteria (bacteriophages), have the potential to alter the function and structure of the microbiome via gene transfer and host lysis. Viral-induced microbiome changes can directly and indirectly influence host health and disease. The contribution of viruses towards disease pathogenesis is therefore an important area for research in ME/CFS. Recent advancements in sequencing technology and bioinformatics now allow more comprehensive and inclusive investigations of human microbiomes. However, as the number of microbiome studies increases, the need for greater consistency in study design and analysis also increases. Comparisons between different ME/CFS microbiome studies are difficult because of differences in patient selection and diagnosis criteria, sample processing, genome sequencing and downstream bioinformatics analysis. It is therefore important that microbiome studies adopt robust, reproducible and consistent study design to enable more reliable and valid comparisons and conclusions to be made between studies. This article provides a comprehensive review of the current evidence supporting microbiome alterations in ME/CFS patients. Additionally, the pitfalls and challenges associated with microbiome studies are discussed.
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Harnessing the Power of Microbiome Assessment Tools as Part of Neuroprotective Nutrition and Lifestyle Medicine Interventions.
Toribio-Mateas, M
Microorganisms. 2018;6(2)
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This is a practical review written by a clinician for other clinicians. It draws from an extensive body of evidence on the links between the gut microbes (bacteria amongst them), called the microbiota, both in health and in a variety of human diseases. The author, who is also a researcher in the communication between the gut and the brain (the gut-brain axis), focuses on the translation of science into simple clinical applications that result in measurable health outcomes, and in particular in neurodegenerative conditions such as Alzheimer's and Parkinson's, but also other less well studied such as Chronic Fatigue Syndrome (CFS). The paper also covers mental health / mood conditions such as anxiety, and depression. Practitioners who work in the area of gut health and use stool tests to assess various imbalances their patients may be experiencing will get the most out this paper. The author takes a look at the physiological processes that influence gastrointestinal as well as brain health and discusses how tools such as the characterisation or "mapping" of commensal bacteria (the bacteria that lives inside our guts normally), along with the identification of potential opportunistic and pathogenic bacteria and parasites, together with knowledge of molecules such as short chain fatty acids or zonulin can enable better clinical decision making by nutrition and lifestyle medicine practitioners. The paper also includes a valuable discussion on patient-reported outcome measures (PROMs), and particularly on the use of MYMOP by practitioners as a validated tool to collect insight from exposure to real world data in clinical practice.
Abstract
An extensive body of evidence documents the importance of the gut microbiome both in health and in a variety of human diseases. Cell and animal studies describing this relationship abound, whilst clinical studies exploring the associations between changes in gut microbiota and the corresponding metabolites with neurodegeneration in the human brain have only begun to emerge more recently. Further, the findings of such studies are often difficult to translate into simple clinical applications that result in measurable health outcomes. The purpose of this paper is to appraise the literature on a select set of faecal biomarkers from a clinician’s perspective. This practical review aims to examine key physiological processes that influence both gastrointestinal, as well as brain health, and to discuss how tools such as the characterisation of commensal bacteria, the identification of potential opportunistic, pathogenic and parasitic organisms and the quantification of gut microbiome biomarkers and metabolites can help inform clinical decisions of nutrition and lifestyle medicine practitioners.
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The gut microbiome and irritable bowel syndrome.
Menees, S, Chey, W
F1000Research. 2018;7
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This study is a review of role of gut microbiome plays in the pathophysiology of Irritable bowel syndrome (IBS) sufferers. The author’s main objective was to identify the biomarkers that may lead into diagnosing and choosing best available therapy available from various interventions available for IBS that targets the gut microbiome, such as prebiotics, probiotics, non-absorbable antibiotics, diet and faecal microbial transplant (FMT). The authors concluded that to enable the right treatment for IBS sufferers it would be better to understand what constitutes a healthy gut rather than deciphering what is abnormal.
Abstract
Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders encountered in clinical practice. It is a heterogeneous disorder with a multifactorial pathogenesis. Recent studies have demonstrated that an imbalance in gut bacterial communities, or "dysbiosis", may be a contributor to the pathophysiology of IBS. There is evidence to suggest that gut dysbiosis may lead to activation of the gut immune system with downstream effects on a variety of other factors of potential relevance to the pathophysiology of IBS. This review will highlight the data addressing the emerging role of the gut microbiome in the pathogenesis of IBS and review the evidence for current and future microbiome based treatments.
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Factors Affecting Gastrointestinal Microbiome Development in Neonates.
Chong, CYL, Bloomfield, FH, O'Sullivan, JM
Nutrients. 2018;10(3)
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This narrative review looks at factors affecting the development of the gastrointestinal (GI) microbiome, before, during and after birth. Animal studies suggest that composition and activity of the microbiome affects the structural and functional development of the GI tract. Although evidence is still limited, it is now believed that microbial colonisation starts in utero (before birth). Mode of birth, vaginal versus caesarean section (CS), appears to play an important role in the development of the gut microbiome and can lead to long-term metabolic and immunological consequences, including a higher risk for a number of conditions in those born by CS. Likewise, breast-feeding versus formula-feeding can affect the microbiome composition. These differences are attributed to both bacteria being transferred directly through breast milk and prebiotic factors in breast milk. Maternal and infant perinatal (during birth) exposure to antibiotics has been linked to an increased risk of several conditions, including asthma, obesity, inflammatory bowel disease and other allergic and inflammatory conditions in children. Other factors that appear to affect the development of the microbiome in infants include maternal lifestyle (e.g. rural versus urban), maternal diet, and environment, in particular, staying in a Neonatal Intensive Care Unit. A limitation the authors point out in comparing study results is that different techniques, both culture based and non-culture based, are used for determining the bacterial microflora.
Abstract
The gut microbiome is established in the newborn period and is recognised to interact with the host to influence metabolism. Different environmental factors that are encountered during this critical period may influence the gut microbial composition, potentially impacting upon later disease risk, such as asthma, metabolic disorder, and inflammatory bowel disease. The sterility dogma of the foetus in utero is challenged by studies that identified bacteria, bacterial DNA, or bacterial products in meconium, amniotic fluid, and the placenta; indicating the initiation of maternal-to-offspring microbial colonisation in utero. This narrative review aims to provide a better understanding of factors that affect the development of the gastrointestinal (GI) microbiome during prenatal, perinatal to postnatal life, and their reciprocal relationship with GI tract development in neonates.
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Gut microbiota, cognitive frailty and dementia in older individuals: a systematic review.
Ticinesi, A, Tana, C, Nouvenne, A, Prati, B, Lauretani, F, Meschi, T
Clinical interventions in aging. 2018;13:1497-1511
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Cognitive frailty is defined as the existence of both physical frailty and mild cognitive impairment, in the absence of a diagnosis of Alzheimer’s Disease or other form of dementia. As such, is considered to be the main pre-condition to developing dementia. Some recent studies have suggested an association between frailty and the gut microbiota, although little data exists on the links between the microbiome and cognitive health. This systematic review aimed to summarise the links made in the science between the gut microbiome and cognitive impairment and the effects of pre and pro-biotics on cognitive decline. 47 papers were identified (31 on animals and 16 on humans). Whilst a number of animal studies supported the link between cognitive impairment and the gut microbiota, there was a substantial lack of human data, preventing the researchers from formulating any clinical recommendations at this stage. Further research in human subjects is required to further our knowledge on the links between the gut microbiome and various forms of cognitive decline and dementia.
Abstract
Cognitive frailty, defined as the coexistence of mild cognitive impairment symptoms and physical frailty phenotype in older persons, is increasingly considered the main geriatric condition predisposing to dementia. Recent studies have demonstrated that gut microbiota may be involved in frailty physiopathology by promoting chronic inflammation and anabolic resistance. The contribution of gut microbiota to the development of cognitive impairment and dementia is less defined, even though the concept of "gut-brain axis" has been well demonstrated for other neuropsychiatric disorders. The aim of this systematic review was to summarize the current state-of-the-art literature on the gut microbiota alterations associated with cognitive frailty, mild cognitive impairment and dementia and elucidate the effects of pre- or probiotic administration on cognitive symptom modulation in animal models of aging and human beings. We identified 47 papers with original data (31 from animal studies and 16 from human studies) suitable for inclusion according to our aims. We concluded that several observational and intervention studies performed in animal models of dementia (mainly Alzheimer's disease) support the concept of a gut-brain regulation of cognitive symptoms. Modulation of vagal activity and bacterial synthesis of substances active on host neural metabolism, inflammation and amyloid deposition are the main mechanisms involved in this physiopathologic link. Conversely, there is a substantial lack of human data, both from observational and intervention studies, preventing to formulate any clinical recommendation on this topic. Gut microbiota modulation of cognitive function represents, however, a promising area of research for identifying novel preventive and treatment strategies against dementia.
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Probiotic monotherapy and Helicobacter pylori eradication: A systematic review with pooled-data analysis.
Losurdo, G, Cubisino, R, Barone, M, Principi, M, Leandro, G, Ierardi, E, Di Leo, A
World journal of gastroenterology. 2018;24(1):139-149
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Helicobacter pylori (H-pylori) is a parasite that resides in the human stomach and is associated with the development of stomach ulcers, amongst other conditions. Conventional treatment relies on a combination of antibiotics and stomach acid suppressants, however failure rates for standard treatments have been rising and alternatives are required. Probiotics (live bacteria that provide health benefits to their host) have been used alongside antibiotic treatment for H-pylori in some cases to reduce medication side effects. This systematic review of 11 studies including 517 H-pylori infected patients, aimed to assess the effects of probiotic therapy alone on H-pylori status. The study found that the eradication rate of H-pylori with a variety of probiotic strains was 12-16%, compared to a 0% success rate in the placebo groups. Clinically, this rate is low, however the authors conclude that probiotics may have a role to play in a multi-therapy approach for the eradication of H-pylori.
Abstract
AIM: To define probiotic monotherapy effect on Helicobacter pylori (H. pylori) status by performing a systematic review. METHODS Methods of analysis and inclusion criteria were based on PRISMA recommendations. Relevant publications were identified by searching PubMed, MEDLINE, Science Direct, and EMBASE. The end-point was to estimate eradication rate and urea breath test delta value before and after probiotic monotherapy across all studies and, overall, with a pooled data analysis. Adverse events of probiotic therapy were evaluated. The data were expressed as proportions/percentages, and 95%CIs were calculated. For continuous variables, we evaluated the weighted mean difference. Odd ratios (ORs) were calculated according to the Peto method for the comparison of eradication rates between probiotics and placebo. RESULTS Eleven studies were selected. Probiotics eradicated H. pylori in 50 out of 403 cases. The mean weighted eradication rate was 14% (95%CI: 2%-25%, P = 0.02). Lactobacilli eradicated the bacterium in 30 out of 235 patients, with a mean weighted rate of 16% (95%CI: 1%-31%). Saccharomyces boulardii achieved eradication in 6 out of 63 patients, with a pooled eradication rate of 12% (95%CI: 0%-29%). Multistrain combinations were effective in 14 out of 105 patients, with a pooled eradication rate of 14% (95%CI: 0%-43%). In the comparison of probiotics vs placebo, we found an OR of 7.91 in favor of probiotics (95%CI: 2.97-21.05, P < 0.001). Probiotics induced a mean reduction in delta values higher than placebo (8.61% with a 95%CI: 5.88-11.34, vs 0.19% for placebo, P < 0.001). Finally, no significant difference in adverse events was found between probiotics and placebo (OR = 1, 95%CI: 0.06-18.08). CONCLUSION Probiotics alone show a minimal effect on H. pylori clearance, thus suggesting a likely direct role.
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Bariatric Surgery and Precision Nutrition.
Nicoletti, CF, Cortes-Oliveira, C, Pinhel, MAS, Nonino, CB
Nutrients. 2017;9(9)
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Bariatric surgery, including gastric bypass, is the most effective strategy to treat obesity and the associated health complications. The major goal is long-term excess body weight reduction, but weight gain after time does occur in a proportion of patients. There is a wide range of responses to bariatric surgery; the different surgical techniques and genetic background of the individual patient account for this. The interactions between nutrients and genes are complex and have not been fully elucidated. This paper summarises the main literature findings relating nutritional genomics and bariatric surgery. It also describes the importance of nutritional genomics concepts in personalized bariatric management. Points discussed are: The genetic variations associated with obesity and telemore length (a marker for cellular ageing). How bariatric surgery affects epigenetics and the expression of various genes involved in different metabolic pathways. The role of bariatric surgery on gut microbiota. The authors believe that nutritional genomics will soon enable the delivery of precise nutrition recommendations to patients undergoing bariatric surgery, to provide high-risk individuals with personalized treatment and to prevent complications.
Abstract
This review provides a literature overview of new findings relating nutritional genomics and bariatric surgery. It also describes the importance of nutritional genomics concepts in personalized bariatric management. It includes a discussion of the potential role bariatric surgery plays in altering the three pillars of nutritional genomics: nutrigenetics, nutrigenomics, and epigenetics. We present studies that show the effect of each patient's genetic and epigenetic variables on the response to surgical weight loss treatment. We include investigations that demonstrate the association of single nucleotide polymorphisms with obesity phenotypes and their influence on weight loss after bariatric surgery. We also present reports on how significant weight loss induced by bariatric surgery impacts telomere length, and we discuss studies on the existence of an epigenetic signature associated with surgery outcomes and specific gene methylation profile, which may help to predict weight loss after a surgical procedure. Finally, we show articles which evidence that bariatric surgery may affect expression of numerous genes involved in different metabolic pathways and consequently induce functional and taxonomic changes in gut microbial communities. The role nutritional genomics plays in responses to weight loss after bariatric surgery is evident. Better understanding of the molecular pathways involved in this process is necessary for successful weight management and maintenance.