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Effects of a Synbiotic on Plasma Immune Activity Markers and Short-Chain Fatty Acids in Children and Adults with ADHD-A Randomized Controlled Trial.
Yang, LL, Stiernborg, M, Skott, E, Xu, J, Wu, Y, Landberg, R, Arefin, S, Kublickiene, K, Millischer, V, Nilsson, IAK, et al
Nutrients. 2023;15(5)
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Attention deficit hyperactivity disorder (ADHD) is a common childhood-onset neurodevelopmental psychiatric disorder. The core symptoms of the disorder are inattention and hyperactivity/impulsivity. The aim of this study was to explore the effects of Synbiotic 2000 on concentrations of plasma immune activity markers and short-chain fatty acids (SCFAs) in ADHD. This study is a double-blind randomised controlled trial over a period of 9-weeks. Patients (n= 248) were randomly allocated to one of the two treatments: Synbiotic 2000 or placebo. Results show that there was no statistically significant overall effect of Synbiotic 2000 compared to placebo on any analyte analysing all the paediatric and all adult participants as one group. However, age-group stratified analyses showed that plasma levels of several of the analytes were at baseline different in the children compared to in the adults. Authors conclude that Synbiotic 2000, in children with ADHD, reduces markers of intestinal and vascular inflammation, the latter in part through increasing SCFAs levels. Furthermore, they suggest that the findings warrant further studies to determine if persons with ADHD would benefit inflammation-wise from dietary intake of Synbiotic 2000 or a similar synbiotic.
Abstract
Synbiotic 2000, a pre + probiotic, reduced comorbid autistic traits and emotion dysregulation in attention deficit hyperactivity disorder (ADHD) patients. Immune activity and bacteria-derived short-chain fatty acids (SCFAs) are microbiota-gut-brain axis mediators. The aim was to investigate Synbiotic 2000 effects on plasma levels of immune activity markers and SCFAs in children and adults with ADHD. ADHD patients (n = 182) completed the 9-week intervention with Synbiotic 2000 or placebo and 156 provided blood samples. Healthy adult controls (n = 57) provided baseline samples. At baseline, adults with ADHD had higher pro-inflammatory sICAM-1 and sVCAM-1 and lower SCFA levels than controls. Children with ADHD had higher baseline sICAM-1, sVCAM-1, IL-12/IL-23p40, IL-2Rα, and lower formic, acetic, and propionic acid levels than adults with ADHD. sICAM-1, sVCAM-1, and propionic acid levels were more abnormal in children on medication. Synbiotic 2000, compared to placebo, reduced IL-12/IL-23p40 and sICAM-1 and increased propionic acid levels in children on medication. SCFAs correlated negatively with sICAM-1 and sVCAM-1. Preliminary human aortic smooth-muscle-cell experiments indicated that SCFAs protected against IL-1β-induced ICAM-1 expression. These findings suggest that treatment with Synbiotic 2000 reduces IL12/IL-23p40 and sICAM-1 and increases propionic acid levels in children with ADHD. Propionic acid, together with formic and acetic acid, may contribute to the lowering of the higher-than-normal sICAM-1 levels.
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Effect of short-term, high-dose probiotic supplementation on cognition, related brain functions and BDNF in patients with depression: a secondary analysis of a randomized controlled trial.
Schneider, E, Doll, JPK, Schweinfurth, N, Kettelhack, C, Schaub, AC, Yamanbaeva, G, Varghese, N, Mählmann, L, Brand, S, Eckert, A, et al
Journal of psychiatry & neuroscience : JPN. 2023;48(1):E23-E33
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Major depressive disorder (MDD) is often thought of as being solely a mood disorder. However, several studies have shown that sufferers can also experience decreased brain function such as memory loss and poor attention. Current therapies for MDD focus on the balancing of mood and leaves the problem of reduced brain function unattended. The gut microbiota has recently been shown to influence brain function and altered gut microbiota composition has been seen in individuals with MDD. Targeting the gut microbiota may therefore represent a novel target for MDD treatments. This secondary analysis of a randomised control trial aimed to determine whether a probiotic multistrain supplement could improve brain function in 60 individuals with depression. The results showed that probiotics improved the brain function in two different ways, the immediate recall of words, and the improvement of decreased neural function in the hippocampal part of the brain, which has been associated with MDD. It was concluded that probiotic supplementation can enhance verbal episodic memory and improve neural function associated with impaired brain function in MDD. This study could be used by healthcare professionals to understand that the health of the gut microbiota can have an influence on brain function and that probiotics may help individuals with MDD who are suffering from poorer memory.
Abstract
BACKGROUND In major depressive disorder (MDD), cognitive dysfunctions strongly contribute to functional impairments but are barely addressed in current therapies. Novel treatment strategies addressing cognitive symptoms in depression are needed. As the gut microbiota-brain axis is linked to depression and cognition, we investigated the effect of a 4-week high-dose probiotic supplementation on cognitive symptoms in depression. METHODS This randomized controlled trial included 60 patients with MDD, of whom 43 entered modified intention-to-treat analysis. A probiotic supplement or indistinguishable placebo containing maltose was administered over 31 days in addition to treatment as usual for depression. Participant scores on the Verbal Learning Memory Test (VLMT), Corsi Block Tapping Test, and both Trail Making Test versions as well as brain-derived neurotrophic factor levels were assessed at 3 different time points: before, immediately after and 4 weeks after intervention. Additionally, brain activation changes during working memory processing were investigated before and immediately after intervention. RESULTS We found a significantly improved immediate recall in the VLMT in the probiotic group immediately after intervention, and a trend for a time × group interaction considering all time points. Furthermore, we found a time × group interaction in hippocampus activation during working memory processing, revealing a remediated hippocampus function in the probiotic group. Other measures did not reveal significant changes. LIMITATIONS The modest sample size resulting from our exclusion of low-compliant cases should be considered. CONCLUSION Additional probiotic supplementation enhances verbal episodic memory and affects neural mechanisms underlying impaired cognition in MDD. The present findings support the importance of the gut microbiota-brain axis in MDD and emphasize the potential of microbiota-related regimens to treat cognitive symptoms in depression. CLINICAL TRIAL REGISTRATION clinicaltrials.gov identifier NCT02957591.
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Psychobiotic Effects on Anxiety Are Modulated by Lifestyle Behaviors: A Randomized Placebo-Controlled Trial on Healthy Adults.
Morales-Torres, R, Carrasco-Gubernatis, C, Grasso-Cladera, A, Cosmelli, D, Parada, FJ, Palacios-García, I
Nutrients. 2023;15(7)
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The microbiota-gut-brain axis refers to the complex communication system between the human gastrointestinal tract, the micro-organisms which inhabit it, and the peripheral and central nervous systems. In recent years, human trials have linked the microbiome with specific processes that are expected to contribute to well-being. The aim of this study was to assess the effect of a psychobiotic formulation specifically on well-being, exploring the extent to which these effects might be modulated by lifestyle factors such as diet, physical activity, social connectedness, and others. This study was a four week, double-blind, randomised, placebo-controlled trial. Participants were randomised into one of two groups; placebo or probiotic group. Results showed that there were no significant effects of probiotics on a set of psychological measures of well-being. However, further analysis revealed that healthy lifestyle behaviours were significantly correlated with wellbeing across scales. Authors conclude that their findings demonstrate the need of controlling lifestyle variables as a standard practice in human microbiome research and mental health research in general.
Abstract
Psychobiotics are modulators of the Microbiota-Gut-Brain Axis (MGBA) with promising benefits to mental health. Lifestyle behaviors are established modulators of both mental health and the MGBA. This randomized placebo-controlled clinical trial (NCT04823533) on healthy adults (N = 135) tested 4 weeks of probiotic supplementation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175). We assessed effects on wellbeing, quality of life, emotional regulation, anxiety, mindfulness and interoceptive awareness. We then analyzed if lifestyle behaviors modulated probiotic effectiveness. Results showed no significant effects of probiotic intake in whole sample outcomes. Correlational analyses revealed Healthy Behaviors were significantly correlated with wellbeing across scales. Moreover, the linear mixed-effects model showed that the interaction between high scores in Healthy Behaviors and probiotic intake was the single significant predictor of positive effects on anxiety, emotional regulation, and mindfulness in post-treatment outcomes. These findings highlight the relevance of controlling for lifestyle behaviors in psychobiotic and mental health research.
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Effect of prebiotics, probiotics, synbiotics on depression: results from a meta-analysis.
Zhang, Q, Chen, B, Zhang, J, Dong, J, Ma, J, Zhang, Y, Jin, K, Lu, J
BMC psychiatry. 2023;23(1):477
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Major depressive disorder (MDD) is a mood disorder that impairs psychosocial function and quality of life. Recent studies show that prebiotics, probiotics, and synbiotics reveal a novel way to treat psychiatric disorders such as depression through the microbiota-gut-brain axis. The aim of this study was to evaluate the effectiveness of prebiotics, probiotics and synbiotics in alleviating depressive symptoms. This study was a meta-analysis of thirteen studies with a total of 786 participants who were allocated to the intervention group (n=427) and the placebo group (n=359). Results showed that the overall effects of probiotics, prebiotics and synbiotics on depressive symptoms were significantly superior to those of placebo. Additionally, biological sex was a vital factor that influenced patients’ responses to the treatment. Authors concluded that agents that manipulate gut microbiota might become a novel approach to treat patients with mild-to-moderate depression.
Abstract
Accumulating studies have shown the effects of gut microbiota management tools in improving depression. We conducted a meta-analysis to evaluate the effects of prebiotics, probiotics, and synbiotics on patients with depression. We searched six databases up to July 2022. In total, 13 randomized controlled trials (RCTs) with 786 participants were included. The overall results demonstrated that patients who received prebiotics, probiotics or synbiotics had significantly improved symptoms of depression compared with those in the placebo group. However, subgroup analysis only confirmed the significant antidepressant effects of agents that contained probiotics. In addition, patients with mild or moderate depression could both benefit from the treatment. Studies with a lower proportion of females reported stronger effects for alleviating depressive symptoms. In conclusion, agents that manipulate gut microbiota might improve mild-to-moderate depression. It is necessary to further investigate the benefits of prebiotic, probiotic and synbiotic treatments relative to antidepressants and follow up with individuals over a longer time before these therapies are implemented in clinical practice.
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Effects of probiotics on neurocognitive outcomes in infants and young children: a meta-analysis.
Lin, FL, Chen, CM, Sun, CK, Cheng, YS, Tzang, RF, Chiu, HJ, Wang, MY, Cheng, YC, Hung, KC
Frontiers in public health. 2023;11:1323511
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There have been increasing investigations into the use of probiotics for treating a variety of neurodevelopmental disorders and also for improvement of neurocognitive outcomes in preterm infants or children. The aim of this study was to provide updated evidence of the therapeutic effects of probiotics on enhancing different neurocognitive functions in infants and children as well as to identify important factors that may influence their treatment efficacies. This study was a meta-analysis of nine randomised controlled studies with 3,026 participants. Results did not show significantly better neurocognitive outcomes in those receiving probiotic treatments than those in the placebo group. However, significantly better neurocognitive development was noted in the probiotic group when focusing on studies that used probiotics for more than six months. Authors concluded that further investigations into the enhancement of therapeutic effects of probiotics on neurocognitive development is required since current evidence is still not strong enough to rule out the beneficial effects of probiotics on neurocognitive development.
Abstract
BACKGROUND Therapeutic efficacies of probiotics in improving neurocognitive functions in infants and young children remained unclear. This meta-analysis focused on different cognitive outcomes in this population. METHODS Major databases were searched electronically from inception to October 2023 to identify randomized controlled trials (RCTs) that investigated the therapeutic efficacy of probiotics in enhancing cognitive functions assessed by standardized tasks. The overall effect size was calculated as standardized mean difference (SMD) based on a random effects model. RESULTS Nine RCTs with 3,026 participants were identified. Both our primary and secondary results demonstrated no significant difference in neurocognitive outcomes between infants/children treated with probiotics and those receiving placebos. However, our subgroup analysis of studies that offered a probiotics treatment course of over six months demonstrated a significantly better neurocognitive outcome than placebos (SMD = 0.21, p = 0.03, two studies with 451 participants), but this finding was based on only two RCTs. CONCLUSION Despite lack of significant therapeutic effects of probiotics on neurocognitive outcomes, our finding of a positive impact of probiotics on neurocognitive development in those undergoing treatment for over six months may provide an important direction for further investigations into the enhancement of therapeutic effects of probiotics on neurocognitive development in infants and young children. SYSTEMATIC REVIEW REGISTRATION PROSPERO CRD42023463412.
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Modulating the Gut Microbiome in Multiple Sclerosis Management: A Systematic Review of Current Interventions.
Tsogka, A, Kitsos, DK, Stavrogianni, K, Giannopapas, V, Chasiotis, A, Christouli, N, Tsivgoulis, G, Tzartos, JS, Giannopoulos, S
Journal of clinical medicine. 2023;12(24)
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Multiple sclerosis (MS) is an autoimmune disease caused by the altered immune system mistakenly attacking the central nervous system. While genetics play a leading causative role in the manifestation of this disease, other contributing environmental factors can also exist, such as a disruption in the intestinal microbial composition. Previous research has shown that the bidirectional communication between the brain's and gut's health, also known as the gut-brain axis, may contribute to the prognosis of MS. Modulating gut microbial composition can be a therapeutic strategy in MS patients to manage symptoms and prevent disease progression. This systematic review assessed different protocols for modulating gut microbial composition, including dietary modifications, probiotic use, intermittent fasting, and faecal microbial transplantation. The review included thirteen studies that compared the effects of the above gut microbial modulation intervention protocols in MS patients with healthy participants. While different dietary modification strategies improved MS symptoms, probiotic supplementations and intermittent fasting reduced inflammation, and faecal microbial transplantation showed promising positive effects in a few reports. Due to the methodological limitations of the included studies, further robust studies are required to evaluate the beneficial effects of gut microbial modulation strategies in reducing the symptoms of MS patients. However, healthcare professionals can use the results of this study to understand the benefits of gut microbial modulation in MS patients.
Abstract
This review attempted to explore all recent clinical studies that have investigated the clinical and autoimmune impact of gut microbiota interventions in multiple sclerosis (MS), including dietary protocols, probiotics, fecal microbiota transplantation (FMT), and intermittent fasting (IF). Methods: Thirteen studies were held between 2011 and 2023 this demonstrated interventions in gut microbiome among patients with MS and their impact the clinical parameters of the disease. These included specialized dietary interventions, the supply of probiotic mixtures, FMT, and IF. Results: Dietary interventions positively affected various aspects of MS, including relapse rates, EDSS disability scores, MS-related fatigue, and metabolic features. Probiotic mixtures showed promising results on MS-related fatigue, EDSS parameters, inflammation; meanwhile, FMT-though a limited number of studies was included-indicated some clinical improvement in similar variables. IF showed reductions in EDSS scores and significant improvement in patients' emotional statuses. Conclusions: In dietary protocols, clinical MS parameters, including relapse rate, EDSS, MFIS, FSS, and MSQoL54 scales, were significantly improved through the application of a specific diet each time. Probiotic nutritional mixtures promote a shift in inflammation towards an anti-inflammatory cytokine profile in patients with MS. The administration of such mixtures affected disability, mood levels, and quality of life among patients with MS. FMT protocols possibly demonstrate a therapeutic effect in some case reports. IF protocols were found to ameliorate EDSS and FAMS scores. All interventional means of gut microbiome modulation provided significant conclusions on several clinical aspects of MS and highlight the complexity in the relationship between MS and the gut microbiome.
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Meta-Analysis Reveals Compositional and Functional Microbial Changes Associated with Osteoporosis.
Akinsuyi, OS, Roesch, LFW
Microbiology spectrum. 2023;11(3):e0032223
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Osteoporosis (OP) is the most common metabolic bone disease associated with aging. Microbiome dysbiosis leading to impaired intestinal immune responses and subsequent production of osteoclastogenic cytokines has been proposed as the mechanism by which gut microbes are associated with osteoporosis. The aim of this study was to identify gut bacteria consistently associated with osteoporosis across different cohorts. This study was a meta-analysis of five studies. Results showed that gut microbial dysbiosis in osteoporosis patients is associated with functional changes, which result in significant changes in metabolites that play a key role in bone metabolism. Authors concluded that their findings set the stage for future studies to provide more comprehensive knowledge on how dysbiosis in the gut microbiome contributes to osteoporosis.
Abstract
Over the past decade, the role of the gut microbiota in many disease states has gained a great deal of attention. Mounting evidence from case-control and observational studies has linked changes in the gut microbiota to the pathophysiology of osteoporosis (OP). Nonetheless, the results of these studies contain discrepancies, leaving the literature without a consensus on osteoporosis-associated microbial signatures. Here, we conducted a comprehensive meta-analysis combining and reexamining five publicly available 16S rRNA partial sequence data sets to identify gut bacteria consistently associated with osteoporosis across different cohorts. After adjusting for the batch effect associated with technical variation and heterogeneity of studies, we observed a significant shift in the microbiota composition in the osteoporosis group. An increase in the relative abundance of opportunistic pathogens Clostridium sensu stricto, Bacteroides, and Intestinibacter was observed in the OP group. Moreover, short-chain-fatty-acid (SCFA) producers, including members of the genera Collinsella, Megasphaera, Agathobaculum, Mediterraneibacter, Clostridium XIV, and Dorea, were depleted in the OP group relative to the healthy control (HC) group. Lactic acid-producing bacteria, including Limosilactobacillus, were significantly increased in the OP group. The random forest algorithm further confirmed that these bacteria differentiate the two groups. Furthermore, functional prediction revealed depletion of the SCFA biosynthesis pathway (glycolysis, tricarboxylic acid [TCA] cycle, and Wood-Ljungdahl pathway) and amino acid biosynthesis pathway (methionine, histidine, and arginine) in the OP group relative to the HC group. This study uncovered OP-associated compositional and functional microbial alterations, providing robust insight into OP pathogenesis and aiding the possible development of a therapeutic intervention to manage the disease. IMPORTANCE Osteoporosis is the most common metabolic bone disease associated with aging. Mounting evidence has linked changes in the gut microbiota to the pathophysiology of osteoporosis. However, which microbes are associated with dysbiosis and their impact on bone density and inflammation remain largely unknown due to inconsistent results in the literature. Here, we present a meta-analysis with a standard workflow, robust statistical approaches, and machine learning algorithms to identify notable microbial compositional changes influencing osteoporosis.
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Lactobacillus rhamnosus CNCM I-3690 decreases subjective academic stress in healthy adults: a randomized placebo-controlled trial.
Wauters, L, Van Oudenhove, L, Accarie, A, Geboers, K, Geysen, H, Toth, J, Luypaerts, A, Verbeke, K, Smokvina, T, Raes, J, et al
Gut microbes. 2022;14(1):2031695
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Previous research has shown a bidirectional relationship between the gut and psychological stress, which could be mediated by intestinal permeability followed by an immune and inflammatory response. However, the exact mechanisms of this relationship are yet to be elucidated. This randomised, double-blind, placebo-controlled trial evaluated the beneficial effects of Lactobacillus rhamnosus CNCM I-3690 on intestinal permeability and stress markers during a public speech in healthy students. Participants consumed either milk containing Lactobacillus rhamnosus CNCM I-3690 or acidified milk twice daily for four weeks to assess subjective and objective stress markers and markers of intestinal permeability. Lactobacillus rhamnosus CNCM I-3690 reduced the stress-induced hyperpermeability to mannitol and subjective stress markers (State-Trait Anxiety Inventory/ STAI). A subgroup of healthy students with stress-induced cortisol >P90 of baseline showed a reduction in perceived stress score following Lactobacillus rhamnosus CNCM I-3690 intervention. To evaluate the additional effects of Lactobacillus rhamnosus CNCM I-3690 on stress and gut health, further robust studies are needed. Healthcare professionals can use the findings of this study to understand the anxiolytic effects of Lactobacillus rhamnosus CNCM I-3690.
Abstract
Psychological stress negatively affects the intestinal barrier function in animals and humans. We aimed to study the effect of Lactobacillus rhamnosus CNCM I-3690 on intestinal permeability and stress-markers during public speech. Healthy students were randomized to L. rhamnosus-containing (test) or acidified (placebo) milk consumed twice daily for 4 weeks, with 46 subjects per treatment group. Small intestinal permeability was quantified by a 2 h urinary lactulose-mannitol ratio (LMR, primary outcome), fractional excretion of lactulose (FEL) and mannitol (FEM). Salivary cortisol, State-Trait Anxiety Inventory (STAI) and Perceived Stress scores (PSS) were collected. No between-treatment differences were found for LMR (p = .71), FEL or FEM. Within-treatment analyses showed similar LMR and FEL but a stress-induced increase of FEM with the placebo (p < .05) but not test product. Despite a similar increase in salivary cortisol, the stress-induced increase in STAI was significantly lower with the test product vs. placebo (p = .01). Moreover, a stress-preventative effect of the probiotic was found for PSS and more pronounced in subjects with high stress-induced cortisol (p = .01). While increased FEM was mediated by salivary cortisol levels, the effect of the test product on subjective stress was not mediated by changes in FEM. No serious adverse events occurred. In conclusion, we demonstrated that L. rhamnosus CNCM I-3690 prevented stress-induced hyperpermeability to mannitol. Subjective but not objective stress-markers were reduced with L. rhamnosus vs. placebo, suggesting anxiolytic effects, which were independent of barrier stabilization and attractive for the reduction of stress in both health and disease. Clinicaltrials.gov, number NCT03408691.
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Effects of Lactiplantibacillus plantarum OLL2712 on Memory Function in Older Adults with Declining Memory: A Randomized Placebo-Controlled Trial.
Sakurai, K, Toshimitsu, T, Okada, E, Anzai, S, Shiraishi, I, Inamura, N, Kobayashi, S, Sashihara, T, Hisatsune, T
Nutrients. 2022;14(20)
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On the Alzheimer’s disease spectrum, which is the most common cause of dementia, the typical symptom at onset is impaired memory. As the disease progresses, other cognitive domains, such as language, visuospatial cognition, and executive function, are impaired, gradually making it impossible to maintain independence in daily life. The aim of this study was to test the protective effects of 12 weeks of supplementation with heat-treated Lactiplantibacillus OLL2712 cells on memory function in older adults. This study was a double-blind placebo-controlled trial in which participants were randomly assigned to the active or placebo group. Results showed that OLL2712 consumption had a protective effect on memory function in older adults. However, there was no significant effect of OLL2712 intake on verbal memory in either of the analyses. Furthermore, in the gut microbiota analysis, the bacterial composition of the active group showed significantly lower abundance ratios of bacterial species linked to inflammation (Lachnoclostridium, Monoglobus, and Oscillibacter). Authors conclude that continuous intake of OLL2712 may be an effective approach to protect memory function in older adults.
Abstract
The use of probiotics is expected to be an intervention in neurodegenerative conditions that cause dementia owing to their ability to modulate neuroinflammatory responses via the microbiome-gut-brain axis. Therefore, we selected Lactiplantibacillus plantarum OLL2712 (OLL2712), the optimal anti-inflammatory lactic acid bacteria strain with high IL-10-inducing activity in immune cells, and aimed to verify its protective effects on memory function in older adults. A 12-week, randomized, double-blind, placebo-controlled trial was performed with older adults over the age of 65 years with declining memory. The participants consumed either powder containing heat-treated OLL2712 cells or placebo. Memory function was assessed using a computer-assisted cognitive test, Cognitrax. Daily dietary nutrient intake was assessed using the Brief-type Self-administered Diet History Questionnaire (BDHQ). The composition of the gut microbiota was analyzed by fecal DNA extraction and 16S rDNA sequencing. Data from 78 participants who completed the entire procedure were analyzed, and significant improvements in composite memory and visual memory scores were observed in the active group, after accounting for the effect of daily nutritional intake (p = 0.044 and p = 0.021, respectively). In addition, the active group had a lower abundance ratio of Lachnoclostridium, Monoglobus, and Oscillibacter genera, which have been reported to be involved in inflammation. The present study suggests that OLL2712 ingestion has protective effects against memory function decline in older adults.
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Evolution of the Human Diet and Its Impact on Gut Microbiota, Immune Responses, and Brain Health.
González Olmo, BM, Butler, MJ, Barrientos, RM
Nutrients. 2021;13(1)
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One explanation for the increased prevalence in chronic disease and mental illness is from the evolutionary perspective. This suggests the rapid shift in diet towards processed foods in the past 200 years has not allowed for sufficient adaptation of the gut microbiome. The gut microbiome plays an important role in the digestive, immune and nervous systems via the gut-brain axis, and may be a key factor in modulating inflammation and disease. The aim of this review is to discuss how what we eat affects the immune system and impacts our brain health. The literature currently shows significant associations between the Western diet and its impact on the health of the gut microbiome and the brain. Increased intake of saturated fats, refined carbohydrates and sugar, coupled with a reduction in fiber, negatively impacts the digestive system and elicits an immune response. This response can lead to neuroinflammation, which is now found to be associated with deficits in learning and memory, as well as increased rates of neurodegenerative disease and depression. Based on the existing literature, the authors conclude the human gut microbiome has not had sufficient time to adapt to many modern foods, thus leading to inflammation and disease. The authors recommend that a diet composed of natural whole foods with minimal processing can help prevent and alleviate some of the burden caused by chronic disease, and suggest future studies focus on improving techniques to evaluate neuroinflammation in humans.
Abstract
The relatively rapid shift from consuming preagricultural wild foods for thousands of years, to consuming postindustrial semi-processed and ultra-processed foods endemic of the Western world less than 200 years ago did not allow for evolutionary adaptation of the commensal microbial species that inhabit the human gastrointestinal (GI) tract, and this has significantly impacted gut health. The human gut microbiota, the diverse and dynamic population of microbes, has been demonstrated to have extensive and important interactions with the digestive, immune, and nervous systems. Western diet-induced dysbiosis of the gut microbiota has been shown to negatively impact human digestive physiology, to have pathogenic effects on the immune system, and, in turn, cause exaggerated neuroinflammation. Given the tremendous amount of evidence linking neuroinflammation with neural dysfunction, it is no surprise that the Western diet has been implicated in the development of many diseases and disorders of the brain, including memory impairments, neurodegenerative disorders, and depression. In this review, we discuss each of these concepts to understand how what we eat can lead to cognitive and psychiatric diseases.