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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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Gut feelings: A randomised, triple-blind, placebo-controlled trial of probiotics for depressive symptoms.
Chahwan, B, Kwan, S, Isik, A, van Hemert, S, Burke, C, Roberts, L
Journal of affective disorders. 2019;253:317-326
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Depression is a debilitating psychiatric disorder that is the leading cause of disability world-wide. Multiple causes of depression have been identified, including genetic, neurological, inflammatory, personality, cognitive, and environmental factors. The aim of this study was to investigate the effectiveness of the multispecies probiotic Ecologic® Barrier for reducing symptoms in adults with mild to severe levels of depression. The study was a triple-blinded parallel, placebo-controlled randomised clinical trial. Participants were randomly allocated into two groups; probiotic and placebo. 71 participants with depressive symptoms were recruited and allocated sequentially over 12 months. Results indicate that all participants across both probiotic and placebo groups exhibited a reduction in depressive symptoms over the time-period of the trial. Thus, the routine involved with daily preparation and consumption of the probiotic and scheduled appointments, as well as involvement in these behaviours with the aim of seeking improvement in depressive symptoms had positive impacts on mood, irrespective of whether the probiotic or placebo was consumed. Authors conclude that their findings offer evidence to indicate that probiotic consumption can exert change on cognitive patterns associated with depression.
Expert Review
Conflicts of interest:
None
Take Home Message:
- This study offers evidence to indicate that probiotic consumption can exert change on cognitive patterns associated with depression.
- The study suggests that probiotics, rather than having a direct effect on depressive symptoms, potentially act on immune system activity, inflammation and gut barrier integrity which contribute to the expression of depression.
- Probiotics may be a useful adjunct to potentiate the effects of other therapies, such as CBT.
- This study points to the validity of managing physical health as part of mental health treatment.
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
With evidence suggesting that decreased gut barrier function and inflammation are correlated with depression, this study set out to determine the effect of consumption of probiotic supplements on depressive symptoms from a sample of 71 participants with depression. The study was a triple-blinded parallel, placebo-controlled randomised clinical trial conducted over 8 weeks in Australia. Pre and post intervention measures of symptoms and vulnerability markers of depression as well as gut microbiota were compared alongside psychological variables and gut microbiota composition to non-depressed, placebo and probiotic groups. All the clinical trial participants demonstrated an improvement in symptoms – participants in the probiotic group demonstrated a significantly greater reduction in cognitive reactivity compared with the placebo group. Probiotics did not significantly alter the microbiota of depressed individuals, however a significant correlation was found between Ruminococcus gnavus and one of the metrics for depression.
Clinical practice applications:
This study was small and carried out over a short period of time. While significant results were found, which signify potential considerations for clinical practice, the results from this study do not offer evidence that the probiotics used had a direct effect on depressive symptoms – they suggest that probiotics potentially act on cognitive processes contributing to depression which may include immune system activity, inflammation, and gut barrier integrity. Overall, this study offers evidence to indicate that probiotic consumption can exert change on cognitive patterns associated with depression. In clinical practice, probiotics may be a useful adjunct to potentiate the effects of therapies, such as CBT. Finally, the use of probiotics promotes the concept of managing physical health as part of mental health treatment.
Considerations for future research:
These preliminary results are promising and offer a number of future research and clinical avenues to build upon. The results do however, indicate that a longer trial may be needed to fully assess the effects of probiotics on mood and the mechanisms by which probiotics may be influencing this. The study also suggests that further research using a range of concentrations in a dose response study may be warranted to determine the optimal dose; a greater dose over a longer period may produce detectable changes in microbiota as well as further differences in psychological data.
Abstract
BACKGROUND Depression is the leading cause of disability worldwide; with evidence suggesting that decreased gut barrier function and inflammation are correlated with depressive symptoms. We conducted a clinical trial to determine the effect of consumption of probiotic supplements (Winclove's Ecologic® Barrier) on depressive symptoms in a sample of participants with mild to severe depression. METHOD 71 participants were randomly allocated to either probiotic or placebo, which was, consumed daily over eight weeks. Pre- and post-intervention measures of symptoms and vulnerability markers of depression as well as gut microbiota composition were compared. Clinical trial participants were also compared on psychological variables and gut microbiota composition to a non-depressed group (n = 20). RESULTS All clinical trial participants demonstrated improvement in symptoms, suggesting non-specific therapeutic effects associated with weekly monitoring visits. Participants in the probiotic group demonstrated a significantly greater reduction in cognitive reactivity compared with the placebo group, particularly in the mild/moderate subgroup. Probiotics did not significantly alter the microbiota of depressed individuals, however, a significant correlation was found between Ruminococcus gnavus and one depression metric. LIMITATIONS There was a high attrition rate, which may be attributed to weekly monitoring visits. Additionally, modulation of the gut microbiota may need more specific testing to distinguish subtle changes. CONCLUSIONS While microbiota composition was similar between all groups, probiotics did affect a psychological variable associated with susceptibility to depression. Further research is needed to investigate how probiotics can be utilised to modify mental wellbeing, and whether they can act as an adjunct to existing treatments.
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Broccoli consumption affects the human gastrointestinal microbiota.
Kaczmarek, JL, Liu, X, Charron, CS, Novotny, JA, Jeffery, EH, Seifried, HE, Ross, SA, Miller, MJ, Swanson, KS, Holscher, HD
The Journal of nutritional biochemistry. 2019;63:27-34
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Diet affects metabolic and gastrointestinal diseases, with the microbiome considered to be a mediating factor. Broccoli is a good source of fibre and phytochemicals including glucosinolates. The aim of this investigator-blinded, controlled feeding, randomised, crossover study was to evaluate the effects of broccoli on the composition and function of the microbiome. 18 healthy adults received 200 g cooked broccoli and 20 g raw daikon radish per day for 18 days in addition to a controlled, brassica-free diet or the same diet without the broccoli and daikon radish, with a 24-day washout period. A statistically significant increase in the ratio of Bacteroidetes to Firmicutes was observed following the broccoli intervention. When stratified by BMI above or below 25, this increase was only seen in those with a lower BMI whilst those with a higher BMI displayed a decrease in the ratio, although the latter was not statistically significant. In those with the lower BMI, there was also a correlation between the changes in the microbiota composition and glucosinolate metabolites. It was predicted that the involved changes would affect the functions of the endocrine system, transport and catabolism and energy metabolism. The authors concluded that eating broccoli may affect both the composition and the function of the microbiome.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Broccoli consumption at dosages of 200g per day were shown to change the composition of gastrointestinal microbiota, increasing Bacteroidetes and decreasing Firmicutes, and impact their function
- The observed results were strongest in those with a BMI of less than 26
- While interesting, the study only included 18 participants and therefore the results should be further confirmed.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Introduction
There is growing evidence linking dysbiosis of the gastrointestinal microbiota and diet-induced gastrointestinal and metabolic diseases. Both long-term and acute dietary changes, fasting, eating frequency, and consumption of specific fibres and food phytochemicals play a role in shaping the composition and function of the microbiota, although evidence is lacking for specific foods. This study aimed to determine the impact of broccoli intake on the number of bacterial strains and their functional capacity.
Methods
This was a single-blind, randomised, crossover, complete feeding intervention. Study participants were healthy adults (n=18, females =10). Participants were requested to not eat Brassica vegetables for 3 weeks before the start of the study.
Subjects participated in two 18-day diet periods separated by a 24-hour washout, during which breakfast and dinner were consumed on site to observe compliance. The control diet was prepared using traditional American foods, excluding all Brassica vegetables. During the broccoli intervention period, participants consumed the same base diet with the addition of 200g of broccoli.
Faecal samples were collected on day 1, and day 16. Quantitative polymerase chain reaction was performed on bacterial strains. On day 17, time series plasma sampling and 24-hour urine collection was done.
Results
There was no difference in alpha diversity (a measure of microbiome diversity within a sample) between the two treatment periods. This indicates that no bacterial species were extinguished by broccoli treatment. Beta diversity analysis (a measure of the (dis)similarity between samples) indicated that bacterial communities were impacted by treatment (P=0.03).
After broccoli consumption, Bacteroidetes increased by 10% (P =0.03), while Firmicutes decreased by 8% (P=0.05). Overall the ratio of Bacteroidetes to Firmicutes increased by 37% (P=0.01) versus a 5% decrease in the control period. The Bacteroides genus increased by 6% (P=0.02) versus a 2% decrease in the control period.
Interestingly, the effects were most strong in those with a lower BMI (< 26 kg/m2) who had an increase in metabolites after broccoli consumption. Algorithms to predict the function of the microbiota showed that broccoli increased endocrine (P=0.05), energy metabolism (P=0.01), transport and catabolism (P=0.04) pathways.
Conclusion
Broccoli intake, at 200g daily, changes the composition and potentially impacts the function of the gut microbiota.
Clinical practice applications:
- Studies like this allow practitioners to focus on specific foods in specific quantities to positively alter the microbiota and their function
- Cruciferous vegetables, like broccoli, kale, cauliflower, cabbage, Brussel sprouts, are an important group as they contain fibre and phytonutrients such as glucosinolates. These compounds can be metabolised by the microbiota into active compounds with health benefits. This study has shown the bidirectional benefit of broccoli consumption in that it can positively impact the function and composition of the microbiota
- Interestingly, the results in this small study were driven by participants with a BMI of less than 26. Sub-group analysis found no statistically significant relationships in participants with BMI >26
- It is worth noting that it is possible that the addition of 5g of fibre from the broccoli is also contributing to the changes observed.
Considerations for future research:
- Larger, controlled feeding studies that isolate specific foods to identify their effects on the microbiota are needed
- Genetic sequencing for only a few bacterial myrosinases has been completed and therefore future studies should aim to assess the metabolic capabilities in faecal samples such as myrosinase activity
- While this study and others have shown changes in the types of bacteria after cruciferous vegetable consumption the consistency of results has been mixed potentially due to differing study designs and treatment dosages. Further studies to clarify and confirm these results would be beneficial
- To assess the function of the microbiota a predictive algorithm was used. This requires experimental confirmation by such methods as metabolite profiling and whole genome shotgun sequencing.
Abstract
The human gastrointestinal microbiota is increasingly linked to health outcomes; however, our understanding of how specific foods alter the microbiota is limited. Cruciferous vegetables such as broccoli are a good source of dietary fiber and phytonutrients, including glucosinolates, which can be metabolized by gastrointestinal microbes. This study aimed to determine the impact of broccoli consumption on the gastrointestinal microbiota of healthy adults. A controlled feeding, randomized, crossover study consisting of two 18-day treatment periods separated by a 24-day washout was conducted in healthy adults (n=18). Participants were fed at weight maintenance with the intervention period diet including 200 g of cooked broccoli and 20 g of raw daikon radish per day. Fecal samples were collected at baseline and at the end of each treatment period for microbial analysis. Beta diversity analysis indicated that bacterial communities were impacted by treatment (P=.03). Broccoli consumption decreased the relative abundance of Firmicutes by 9% compared to control (P=.05), increased the relative abundance of Bacteroidetes by 10% compared to control (P=.03) and increased Bacteroides by 8% relative to control (P=.02). Furthermore, the effects were strongest among participants with body mass index <26 kg/m2, and within this group, there were associations between bacterial relative abundance and glucosinolate metabolites. Functional prediction revealed that broccoli consumption increased the pathways involved in the functions of the endocrine system (P=.05), transport and catabolism (P=.04), and energy metabolism (P=.01). These results reveal that broccoli consumption affects the composition and function of the human gastrointestinal microbiota.
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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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The Role of Dietary Fiber in Rheumatoid Arthritis Patients: A Feasibility Study.
Häger, J, Bang, H, Hagen, M, Frech, M, Träger, P, Sokolova, MV, Steffen, U, Tascilar, K, Sarter, K, Schett, G, et al
Nutrients. 2019;11(10)
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Rheumatoid arthritis (RA) is a chronic, autoimmune inflammatory musculoskeletal disorder, affecting around 1% of the world population. Risk factors are genetic and environmental, with diet appearing to be an important environmental trigger. The impacts of diet on the gut microbiota are well studied, including the ability of the gut microbiome to manipulate the immune system. This small feasibility study of 36 patients with RA aimed to examine the effect of short-term high fibre dietary supplementation on T-reg cell numbers (cells which regulate the immune system). A high fibre bar was provided to study subjects for 28 days and measurements taken of immune and inflammation markers, bone erosion, gut bacterial changes and quality of life. The authors found a positive improvement to patient immune systems at the end of the intervention, as well as decreased markers of bone erosion. Physical functioning and quality of life were also reported as significantly improved. Whilst this is a small uncontrolled trial, the results support increasing the fibre intake when working with RA clients.
Abstract
Short-chain fatty acids are microbial metabolites that have been shown to be key regulators of the gut-joint axis in animal models. In humans, microbial dysbiosis was observed in rheumatoid arthritis (RA) patients as well as in those at-risk to develop RA, and is thought to be an environmental trigger for the development of clinical disease. At the same time, diet has a proven impact on maintaining intestinal microbial homeostasis. Given this association, we performed a feasibility study in RA patients using high-fiber dietary supplementation with the objective to restore microbial homeostasis and promote the secretion of beneficial immunomodulatory microbial metabolites. RA patients (n = 36) under routine care received daily high-fiber bars or cereals for 28 days. Clinical assessments and laboratory analysis of immune parameters in blood and stool samples from RA patients were done before and after the high-fiber dietary supplementation. We observed an increase in circulating regulatory T cell numbers, favorable Th1/Th17 ratios, as well as decreased markers of bone erosion in RA patients after 28 days of dietary intervention. Furthermore, patient-related outcomes of RA improved. Based on these results, we conclude that controlled clinical studies of high-fiber dietary interventions could be a viable approach to supplement or complement current pharmacological treatment strategies.
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The combination of sport and sport-specific diet is associated with characteristics of gut microbiota: an observational study.
Jang, LG, Choi, G, Kim, SW, Kim, BY, Lee, S, Park, H
Journal of the International Society of Sports Nutrition. 2019;16(1):21
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Regular exercise offers many health benefits. Research also suggests that regular exercise plays a beneficial role for the structure and diversity of gut microbiota. However, diets high in monosaccharides (simple sugars) and protein, and low in fibre, which are commonly consumed by athletes may have a negative effect on the gut microbiota. The aim of this observational study was to investigate the long-term effects of a specific exercise type and athletes’ diets on gut microbiota. 15 men in their 20s who were bodybuilders, elite distance runners or healthy controls without regular exercise habits were recruited for this study. Gut microbiota characteristics, dietary intake, and body composition were compared. There were significant differences in body composition according to exercise type and dietary habits, with bodybuilders having most lean tissue and distance runners the lowest body fat percentage. Dietary patterns were characterised by high protein intake for bodybuilders and low fibre intake for distance runners. Fat consumption did not vary between groups. Gut microbiota diversity did not differ between groups but there were differences in the relative abundance of certain intestinal microbes, with potentially negative effects.
Abstract
BACKGROUND Recently, gut microbiota have been studied extensively for health promotion, disease prevention, disease treatment, and exercise performance. It is recommended that athletes avoid dietary fiber and resistant starch to promote gastric emptying and reduce gastrointestinal distress during exercise, but this diet may reduce microbial diversity and compromise the health of the athlete's gut microbiota. OBJECTIVE This study compared fecal microbiota characteristics using high-throughput sequencing among healthy sedentary men (as controls), bodybuilders, and distance runners, as well as the relationships between microbiota characteristics, body composition, and nutritional status. METHODS Body composition was measured using DXA, and physical activity level was assessed using IPAQ. Dietary intake was analyzed with the computerized nutritional evaluation program. The DNA of fecal samples was extracted and it was sequenced for the analysis of gut microbial diversity through bioinformatics cloud platform. RESULTS We showed that exercise type was associated with athlete diet patterns (bodybuilders: high protein, high fat, low carbohydrate, and low dietary fiber diet; distance runners: low carbohydrate and low dietary fiber diet). However, athlete type did not differ in regard to gut microbiota alpha and beta diversity. Athlete type was significantly associated with the relative abundance of gut microbiota at the genus and species level: Faecalibacterium, Sutterella, Clostridium, Haemophilus, and Eisenbergiella were the highest (p < 0.05) in bodybuilders, while Bifidobacterium and Parasutterella were the lowest (p < 0.05). At the species level, intestinal beneficial bacteria widely used as probiotics (Bifidobacterium adolescentis group, Bifidobacterium longum group, Lactobacillus sakei group) and those producing short chain fatty acids (Blautia wexlerae, Eubacterium hallii) were the lowest in bodybuilders and the highest in controls. In addition, aerobic or resistance exercise training with an unbalanced intake of macronutrients and low intake of dietary fiber led to similar diversity of gut microbiota. Specifically, daily protein intake was negatively correlated with operation taxonomic unit (r = - 0.53, p < 0.05), ACE (r = - 0.51, p < 0.05), and Shannon index (r = - 0.64, p < 0.01) in distance runners.. CONCLUSION Results suggest that high-protein diets may have a negative impact on gut microbiota diversity for athletes, while athletes in resistance sports that carry out the high protein low carbohydrates diet demonstrate a decrease in short chain fatty acid-producing commensal bacteria.
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Dietary supplementation with inulin-propionate ester or inulin improves insulin sensitivity in adults with overweight and obesity with distinct effects on the gut microbiota, plasma metabolome and systemic inflammatory responses: a randomised cross-over trial.
Chambers, ES, Byrne, CS, Morrison, DJ, Murphy, KG, Preston, T, Tedford, C, Garcia-Perez, I, Fountana, S, Serrano-Contreras, JI, Holmes, E, et al
Gut. 2019;68(8):1430-1438
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Literature shows that higher intakes of dietary fibre are associated with a reduced risk of type 2 diabetes. The main aim of this study was to elucidate the underlying mechanisms behind improvements in glucose homeostasis following long-term delivery of propionate (a short-chain fatty acid produced by human gut microbiota in response to dietary fibre) to the human colon. The study is a randomised, double-blind, placebo-controlled cross over trial. Fourteen participants randomly received 20 g/day of a low-fermentable fibre control, a high-fermentable fibre control and inulin-propionate ester (IPE) for 42 days each. Results indicate that stool concentrations of short-chain fatty acids were not different following the three supplementation periods. Furthermore, dietary supplementation with 20 g/day IPE promoted no superior impacts on measures of glucose homeostasis compared with inulin (high-fermentable fibre), yet both IPE and inulin improved insulin resistance relative to cellulose (low-fermentable fibre). Authors conclude that manipulating the colonic fermentation profile of a dietary fibre in favour of propionate promotes selective effects on the mechanisms that contribute to metabolic dysregulation.
Abstract
OBJECTIVE To investigate the underlying mechanisms behind changes in glucose homeostasis with delivery of propionate to the human colon by comprehensive and coordinated analysis of gut bacterial composition, plasma metabolome and immune responses. DESIGN Twelve non-diabetic adults with overweight and obesity received 20 g/day of inulin-propionate ester (IPE), designed to selectively deliver propionate to the colon, a high-fermentable fibre control (inulin) and a low-fermentable fibre control (cellulose) in a randomised, double-blind, placebo-controlled, cross-over design. Outcome measurements of metabolic responses, inflammatory markers and gut bacterial composition were analysed at the end of each 42-day supplementation period. RESULTS Both IPE and inulin supplementation improved insulin resistance compared with cellulose supplementation, measured by homeostatic model assessment 2 (mean±SEM 1.23±0.17 IPE vs 1.59±0.17 cellulose, p=0.001; 1.17±0.15 inulin vs 1.59±0.17 cellulose, p=0.009), with no differences between IPE and inulin (p=0.272). Fasting insulin was only associated positively with plasma tyrosine and negatively with plasma glycine following inulin supplementation. IPE supplementation decreased proinflammatory interleukin-8 levels compared with cellulose, while inulin had no impact on the systemic inflammatory markers studied. Inulin promoted changes in gut bacterial populations at the class level (increased Actinobacteria and decreased Clostridia) and order level (decreased Clostridiales) compared with cellulose, with small differences at the species level observed between IPE and cellulose. CONCLUSION These data demonstrate a distinctive physiological impact of raising colonic propionate delivery in humans, as improvements in insulin sensitivity promoted by IPE and inulin were accompanied with different effects on the plasma metabolome, gut bacterial populations and markers of systemic inflammation.
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Treatment of Active Crohn's Disease With an Ordinary Food-based Diet That Replicates Exclusive Enteral Nutrition.
Svolos, V, Hansen, R, Nichols, B, Quince, C, Ijaz, UZ, Papadopoulou, RT, Edwards, CA, Watson, D, Alghamdi, A, Brejnrod, A, et al
Gastroenterology. 2019;156(5):1354-1367.e6
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Crohn’s disease (CD) is associated with high morbidity and increased health expenditure. The current paradigm of CD pathogenesis suggests an interaction between environmental factors and the gut microbiome. The main aim of this study was to develop a food diet based on the composition of exclusive enteral nutrition (EEN) and examine the effects on the gut microbiome. This study is a randomised controlled trial (RCT) which recruited healthy adults who were randomly allocated to one of the 2 groups: EEN group or CD-treatment group. The RCT was followed by experiments in animal models to explore the anti-inflammatory effect of CD-treatment and its effect on the gut microbiome in a disease state. Results indicate that when compared to EEN, the CD-treatment induced similar broad-spectrum alterations in the gut microbiome and provided similar efficacy in treating gut inflammation and improving clinical activity in healthy participants. Furthermore, several effects observed in the healthy participants were replicated in the animal experiments which featured microbial dysbiosis (imbalance) which is similar to human CD. Authors conclude that CD-treatment has the potential to be used interchangeably with EEN, especially in adults whom EEN uptake is low, and raises the prospect of long-term dietary maintenance therapy.
Abstract
BACKGROUND & AIMS Exclusive enteral nutrition (EEN) is the only established dietary treatment for Crohn's disease (CD), but its acceptability is limited. There is a need for novel dietary treatments for CD. METHODS We evaluated the effects of an individualized food-based diet (CD-TREAT), with similar composition to EEN, on the gut microbiome, inflammation, and clinical response in a rat model, healthy adults, and children with relapsing CD. Twenty-five healthy adults randomly received EEN or CD-TREAT for 7 days, followed by a 14-day washout period, followed by the alternate diet. Fecal microbiome and metabolome were assessed before and after each diet. HLA-B7 and HLA-B27 transgenic rats with gut inflammation received EEN, CD-TREAT, or standard chow for 4 weeks. Fecal, luminal, and tissue microbiome, fecal metabolites, and gut inflammation were assessed. Five children with active CD activity received CD-TREAT and their clinical activity and calprotectin were evaluated after 8 weeks of treatment. RESULTS For healthy adults, CD-TREAT was easier to comply with and more acceptable than EEN. CD-TREAT induced similar effects to EEN (EEN vs CD-TREAT) on fecal microbiome composition, metabolome, mean total sulfide (increase 133.0 ± 80.5 vs 54.3 ± 47.0 nmol/g), pH (increase 1.3 ± 0.5 vs 0.9 ± 0.6), and the short-chain fatty acids (μmol/g) acetate (decrease 27.4 ± 22.6 vs 21.6 ± 20.4), propionate (decrease 5.7 ± 7.8 vs 5.2 ± 7.9), and butyrate (decrease 7.0 ± 7.4 vs 10.2 ± 8.5). In the rat model, CD-TREAT and EEN produced similar changes in bacterial load (decrease 0.3 ± 0.3 log10 16S rRNA gene copies per gram), short-chain fatty acids, microbiome, and ileitis severity (mean histopathology score decreases of 1.25 for EEN [P = .015] and 1.0 for CD-TREAT [P = .044] vs chow). In children receiving CD-TREAT, 4 (80%) had a clinical response and 3 (60%) entered remission, with significant concurrent decreases in fecal calprotectin (mean decrease 918 ± 555 mg/kg; P = .002). CONCLUSION CD-TREAT replicates EEN changes in the microbiome, decreases gut inflammation, is well tolerated, and is potentially effective in patients with active CD. ClinicalTrials.gov, numbers NCT02426567 and NCT03171246.
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Whole grain-rich diet reduces body weight and systemic low-grade inflammation without inducing major changes of the gut microbiome: a randomised cross-over trial.
Roager, HM, Vogt, JK, Kristensen, M, Hansen, LBS, Ibrügger, S, Mærkedahl, RB, Bahl, MI, Lind, MV, Nielsen, RL, Frøkiær, H, et al
Gut. 2019;68(1):83-93
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Plain language summary
Whole grain consumption has been linked with decreased risk of lifestyle-related diseases. While animal studies have shown the gut microbiome to be a mediator of metabolic health, human studies examining the effect of whole grain intake of the gut remain inconclusive. The aim of this study was to investigate the effects of a whole grain diet on the gut microbiome, gut functionality and biomarkers of metabolic health. In this randomised, controlled, crossover study, 50 participants completed two 8-week dietary intervention periods comprising of a whole grain diet and a refined grain diet with a 6-week washout period. Examinations were done at the beginning and end of each intervention period to assess anthropometry and various plasma and gut markers. This study found that a whole grain diet as compared with a refined grain diet reduced energy intake and body weight as well as circulating markers of inflammation. Contrary to the hypothesis, these benefits were all observed independent of changes in the gut microbiome. Based on these results, the authors conclude higher intake of whole grains should be recommended to those at risk of inflammation-related disease.
Abstract
OBJECTIVE To investigate whether a whole grain diet alters the gut microbiome and insulin sensitivity, as well as biomarkers of metabolic health and gut functionality. DESIGN 60 Danish adults at risk of developing metabolic syndrome were included in a randomised cross-over trial with two 8-week dietary intervention periods comprising whole grain diet and refined grain diet, separated by a washout period of ≥6 weeks. The response to the interventions on the gut microbiome composition and insulin sensitivity as well on measures of glucose and lipid metabolism, gut functionality, inflammatory markers, anthropometry and urine metabolomics were assessed. RESULTS 50 participants completed both periods with a whole grain intake of 179±50 g/day and 13±10 g/day in the whole grain and refined grain period, respectively. Compliance was confirmed by a difference in plasma alkylresorcinols (p<0.0001). Compared with refined grain, whole grain did not significantly alter glucose homeostasis and did not induce major changes in the faecal microbiome. Also, breath hydrogen levels, plasma short-chain fatty acids, intestinal integrity and intestinal transit time were not affected. The whole grain diet did, however, compared with the refined grain diet, decrease body weight (p<0.0001), serum inflammatory markers, interleukin (IL)-6 (p=0.009) and C-reactive protein (p=0.003). The reduction in body weight was consistent with a reduction in energy intake, and IL-6 reduction was associated with the amount of whole grain consumed, in particular with intake of rye. CONCLUSION Compared with refined grain diet, whole grain diet did not alter insulin sensitivity and gut microbiome but reduced body weight and systemic low-grade inflammation. TRIAL REGISTRATION NUMBER NCT01731366; Results.