Effect of combined bifidobacteria supplementation and resistance training on cognitive function, body composition and bowel habits of healthy elderly subjects

Influence of human gut microbiome on the healthy and the neurodegenerative aging

The gut microbiome plays a crucial role in host health throughout the lifespan by influencing brain function during aging. The microbial diversity of the human gut microbiome decreases during the aging process and, as a consequence, several mechanisms increase, such as oxidative stress, mitochondrial dysfunction, inflammatory response, and microbial gut dysbiosis. Moreover, evidence indicates that aging and neurodegeneration are closely related; consequently, the gut microbiome may serve as a novel marker of lifespan in the elderly. In this narrative study, we investigated how the changes in the composition of the gut microbiome that occur in aging influence to various neuropathological disorders, such as mild cognitive impairment (MCI), dementia, Alzheimer's disease (AD), and Parkinson's disease (PD); and which are the possible mechanisms that govern the relationship between the gut microbiome and cognitive impairment. In addition, several studies suggest that the gut microbiome may be a potential novel target to improve hallmarks of brain aging and to promote healthy cognition; therefore, current and future therapeutic interventions have been also reviewed.

Divergent Gut Microbiota: Archaeal and Bacterial Signatures Unveil Unique Patterns in Colombian Cyclists Compared to Weightlifters and Non-Athletes

Engagement in physical activity, across various sports, promotes a diverse microbiota in active individuals. This study examines the gut microbiota of Colombian athletes, specifically weightlifters (n = 16) and road cyclists (n = 13), compared to non-athletes (n = 15). Using Kruskal-Wallis tests, the physical activity level of a group of non-athletic individuals and the sports experience of a group of professional athletes is analyzed. The median age of participants is 24 years, comprising 25 men and 19 women. The microbiota is collected using fecal samples. Participants provided these samples during their pre-competitive stage, specifically during the concentration phase occurring two weeks prior to national competitions. This timing is chosen to capture the microbial composition during a period of heightened physical preparation. Questionnaire responses and microbial composition assessments identify disparities among groups. Microbial composition analysis explores core microbiome, abundance, and taxonomy using Pavian, MicrobiomeAnalyst 2.0, and GraPhlAn. ANCOM-BC2 reveals differentially abundant species. Road cyclists exhibit decreased Bacteria and increased Archaea abundance. Phylum-level variations included Planctomycetes, Acidobacteria, and Proteobacteria, while Bacteroidetes prevailed. Key families influencing gut microbiota are Bacteroidaceae, Muribaculaceae, and Selenomonadaceae. Weightlifters exhibit unique viral and archaeal community connections, while cyclists showed specialized microbial interplay influenced by endurance exercise. Correlation network analysis emphasizes distinctive microbial interactions within athlete groups, shedding light on the impact of physical activities on gut microbiota and athlete health.

Beneficial effects of the probiotics and synbiotics supplementation on anthropometric indices and body composition in adults: A systematic review and meta-analysis

Studies have suggested that probiotics and synbiotics can improve body weight and composition. However, randomized controlled trials (RCTs) demonstrated mixed results. Hence, we performed a systematic review and meta-analysis to evaluate the effectiveness of probiotics and synbiotics on body weight and composition in adults. We searched PubMed/Medline, Ovid/Medline, Scopus, ISI Web of Science, and Cochrane library up to April 2023 using related keywords. We included all RCTs investigating the effectiveness of probiotics and/or synbiotics supplementation on anthropometric indices and body composition among adults. Random-effects models were applied for performing meta-analyses. In addition, we conducted subgroup analyses and meta-regression to explore the non-linear and linear relationship between the length of follow-up and the changes in each outcome. We included a total of 200 trials with 12,603 participants in the present meta-analysis. Probiotics or synbiotics intake led to a significant decrease in body weight (weighted mean difference [WMD]: -0.91 kg; 95% CI: -1.08, -0.75; p < 0.001), body mass index (BMI) (WMD: -0.28 kg/m2 ; 95% CI: -0.36, -0.21; p < 0.001), waist circumference (WC) (WMD: -1.14 cm; 95% CI: -1.42, -0.87; p < 0.001), waist-to-hip ratio (WHR) (WMD: -0.01; 95% CI: -0.01, -0.00; p < 0.001), fat mass (FM) (WMD: -0.92 kg; 95% CI: -1.05, -0.79; p < 0.001), and percentage of body fat (%BF) (WMD: -0.68%; 95% CI: -0.94, -0.42; p < 0.001) compared to controls. There was no difference in fat-free mass (FFM) and lean body mass (LBM). Subgroup analyses indicated that probiotics or synbiotics administered as food or supplement resulted in significant changes in anthropometric indices and body composition. However, compared to controls, FM and %BF values were only reduced after probiotic consumption. Our results showed that probiotics or synbiotics have beneficial effects on body weight, central obesity, and body composition in adults and could be useful as an add on to weight loss products and medications.

Probiotics supplementation or probiotic-fortified products on sarcopenic indices in older adults: systematic review and meta-analysis from recent randomized controlled trials

Introduction: A noteworthy correlation was seen between changes in the gut microbiome and sarcopenia in older adults. Along with increasing research on probiotic supplementation for various medical problems, we aimed to obtain evidence and summarize the effect of probiotic supplementation on sarcopenic indices among older adults. Methods: We utilized PubMed, EBSCO, and Proquest, in addition to manual search using synonyms and variation for 'probiotic,' 'sarcopenia,' and 'older adults.' Randomized controlled trials investigated the utilization of probiotics or probiotic-containing products in older adults with sarcopenic indices including muscle mass and strength. The random-effects model was applied to the meta-analysis process. Results: Seven studies were obtained with 733 pooled older adults. Probiotic supplementation resulted in a significant increase of muscle mass with adjusted SMD (Standardized Mean Difference) of 0.962 (95% CI: 0.288 to 1.635, p = 0.049) using till and trim analysis and muscle strength with SMD of 1.037 (95% CI: 0.077 to 1.996, p = 0.03). However, both outcomes were associated with significantly high heterogeneity (I2 = 89.5% and I2 = 89.9%, respectively). Conclusion: When opposed to a placebo, the probiotic treatment improved the amount of muscle and its endurance based on recent evidence, however, further studies should be done with larger samples and targeted populations.

Bifidobacteria in disease: from head to toe

Bifidobacteria as a strictly anaerobic gram-positive bacteria, is widely distributed in the intestine, vagina and oral cavity, and is one of the first gut flora to colonize the early stages of life. Intestinal flora is closely related to health, and dysbiosis of intestinal flora, especially Bifidobacteria, has been found in a variety of diseases. Numerous studies have shown that in addition to maintaining intestinal homeostasis, Bifidobacteria may be involved in diseases covering all parts of the body, including the nervous system, respiratory system, genitourinary system and so on. This review collects evidence for the variation of Bifidobacteria in typical diseases among various systems, provides mild and effective therapeutic options for those diseases that are difficult to cure, and moves Bifidobacteria from basic research to further clinical applications.

"High dietary live microbe intake is correlated with reduced risk of depressive symptoms: A cross-sectional study of NHANES 2007-2016"

BACKGROUND

Recent research indicated that levels of dietary live microorganisms were inconsistently associated with the prevalence of depressive symptoms. This study aimed to investigate the correlation between consumption of live microorganisms and symptoms of depression.

METHODS

Data on 21,653 study participants were obtained from the National Health and Nutrition Examination Survey (NHANES). Dietary information was assessed using a self-report questionnaire. Depressive status was assessed using the Patient Health Questionnaire (PHQ-9). Generalized linear model, restricted cubic spline (RCS), and subgroup analyses were performed in this study.

RESULTS

After full adjustment for confounders, participants in the moderate-dietary microbe intake group had a lower prevalence of depressive symptoms than those in the lowest intake group [odds ratio (OR): 0.813, 95 % confidence interval (CI): 0.678-0.974, P = 0.026, and pseudo R2 = 0.12]. Participants in the highest-dietary microbe intake group had a lower prevalence of depressive symptoms than those in the lowest intake group (OR: 0.714, 95 % CI: 0.586-0.870, P = 0.001, and pseudo R2 = 0.12). An L-shaped dose-response relationship was observed in the RCS (the P value for nonlinear relationship = 0.007). In subgroup analyses, participants with male identity, normal weight, and high physical activity (PA) level showed a substantial correlation between dietary live microbe consumption and depressive symptoms (all P values for interaction <0.050).

LIMITATIONS

This study was limited by its cross-sectional study design, and self-reported dietary live microbe consumption and depressive symptoms.

CONCLUSIONS

A high dietary live microbe intake was nonlinearly correlated with a lower prevalence of depressive symptoms.

Engraftment of aging-related human gut microbiota and the effect of a seven-species consortium in a pre-clinical model

Human aging is characterized by gut microbiome alteration and differential loss of gut commensal species associated with the onset of frailty. The administration of cultured commensal strains to replenish lost taxa could potentially promote healthy aging. To investigate the interaction of whole microbiomes and administered strains, we transplanted gut microbiota from a frail or healthy elderly subject into germ-free mice. We supplemented the frail-donor recipient group with a defined consortium of taxa (the "S7") that we identified by analyzing healthy aging subjects in our previous studies and whose abundance correlated with health-promoting dietary intervention. Inoculation with a frail or a healthy donor microbiome resulted in differential microbiota compositions in murine recipients 5 weeks post-transplantation. Fecal acetate levels were significantly higher in healthy donor recipient mice than in frail donor recipient mice after 4 weeks. However, the frailty-related phenotype was not replicated in recipient mice with single-dose microbiota transplantation from a healthy and a frail donor. Five S7 species colonized successfully in germ-free mice, with a relatively high abundance of Barnesiella intestinihominis and Eubacterium rectale. The engraftment of five S7 species in germ-free mice increased fecal acetate levels and reduced colon permeability and plasma TNF-ɑ concentration. Supplementation with the S7 in frail-microbiota recipient mice did not increase alpha-diversity but significantly increased the abundance of Barnesiella intestinihominis. S7 supplementation showed the potential for improving spatial reference memory in frail-microbiota recipient mice. Collectively, these data highlight the challenge of elderly microbiota engraftment in the germ-free mouse model but show promise for modulating the gut microbiome of frail elderly subjects by administering an artificial gut microbe consortium associated with healthy aging.

A meta-analysis of the effect of probiotic administration on age-related sarcopenia

Global increase in the prevalence of age-related diseases, such as sarcopenia, highlights the need of recognizing agents that improve muscle health; however, the evidence synthesis on the impact of probiotic administration on sarcopenia is scarce. To summarize and evaluate findings regarding the effect of supplementation with probiotics on sarcopenia, this meta-analysis was conducted. Using databases, including PubMed, SCOPUS, ISI-Web of Science, and Cochrane Library, interventional studies were included if they investigate the effect of probiotic administration on at least one of the components of sarcopenia up to 6 October 2022. Risk of bias evaluation was conducted using the Cochrane quality assessment tool. The random-effects model which takes between-study variations into account was used to obtain the overall effect sizes. The STATA version 14.0 was used for statistical analyses. Overall, 17 studies were included. There was high certainty of evidence that probiotic supplementation has a beneficial effect on muscle mass (kg) (WMD: 0.55, 95% CI: 0.05, 1.05; I 2: 0.0%, p = .995), and muscle function (WMD: 0.13, 95% CI: 0.03, 0.23; I 2: 65.6%, p = .05). Moreover, administration of probiotics for more than 12 weeks significantly increased muscle strength (WMD: 1.16, 95% CI: 0.88, 1.44; I 2: 0.0%, p = .77). However, probiotic supplementation had no effect on anthropometric indices, including body mass index. Probiotic supplementation could improve muscle mass and muscle function in adults more than 55 years old. The beneficial effect of probiotics on muscle strength could appear after 12 weeks of supplementation.

Probiotic supplements are effective in people with cognitive impairment: a meta-analysis of randomized controlled trials

CONTEXT

Cognitive function is a significant concern among the elderly and has a major negative effect on their quality of life. Probiotics have a positive effect on improving cognition, but the exact nature of the association between probiotic supplements and cognitive function is poorly understood.

OBJECTIVE

The purpose of this systematic review was to evaluate how probiotic supplements improve cognitive function.

DATA SOURCES

A systematic search was conducted of the PubMed, Web of Science, the Cochrane Library, Embase, and ClinicalTrials.gov databases for all relevant studies published in English, with no date restrictions.

DATA EXTRACTION

The estimated, pooled results were analyzed with a standardized mean difference (SMD) and a corresponding 95% confidence interval (95%CI). Publication bias was analyzed by the Egger's and Begg's tests. Funnel plots were also constructed to assess the probability of publication bias. The robustness of the results was tested using the method of sequential removal and cumulation of each trial.

DATA ANALYSIS

Overall, the pooled SMD showed significant differences between the probiotic and placebo groups (SMD = 0.64; 95%CI, 0.15-1.12), with significant heterogeneity (I2 = 92%). Subgroup analyses showed a significant effect of probiotics on cognition in the studies involving populations with Alzheimer's disease and cognitive impairment (SMD = 1.34; 95%CI, 0.51-2.16; P < 0.01). In addition, subgroup analysis showed that single probiotic strains, receiving probiotic supplements over 12 weeks, and doses >1 × 109 CFU/g were more beneficial for improving cognitive impairment.

CONCLUSIONS

According to this meta-analysis, probiotic supplementation had a highly significant effect on cognitive function in people with cognitive impairment or Alzheimer's disease. For people without cognitive impairment, probiotic supplementation may be ineffective.

A comprehensive review of Bifidobacterium spp: as a probiotic, application in the food and therapeutic, and forthcoming trends

Recently, more consumers are interested in purchasing probiotic food and beverage products that may improve their immune health. The market for functional foods and beverages that include Bifidobacterium is expanding because of their potential uses in both food and therapeutic applications. However, maintaining Bifidobacterium's viability during food processing and storage remains a challenge. Microencapsulation technique has been explored to improve the viability of Bifidobacterium. Despite the technical, microbiological, and economic challenges, the market potential for immune-supporting functional foods and beverages is significant. Additionally, there is a shift toward postbiotics as a solution for product innovation, a promising postbiotic product that can be incorporated into various food and beverage formats is also introduced in this review. As consumers become more health-conscious, future developments in the functional food and beverage market discussed in this review could serve as a reference for researchers and industrialist.

Effects of human probiotics on memory and psychological and physical measures in community-dwelling older adults with normal and mildly impaired cognition: results of a bi-center, double-blind, randomized, and placebo-controlled clinical trial (CleverAge biota)

Objectives

This study presents results of our randomized clinical trial studying the effect of human probiotics on memory and psychological and physical measures following our study protocol registered at clinicaltrials.gov NCT05051501 and described in detail in our previous paper.

Methods

Community dwelling participants aged between 55 and 80  years were randomly assigned to receive a single dose of 10⁶ colony-forming units of human Streptococcus thermophilus GH, Streptococcus salivarius GH NEXARS, Lactobacilus plantarum GH, and Pediococcus pentosaceus GH or placebo. A cross-over design allowed each group to receive probiotics and placebo for 3  months each in reverse order. A small subset of participants was examined online due to the COVID-19 pandemic. After 6  months a small number of volunteers were additionally assessed after 2  months without any intervention. Primary outcome measures included changes in cognitive functions assessed using brief tests and a neuropsychological battery and changes in mood assessed using validated questionnaires. Secondary outcome measures included changes in self-report and subjective measures using depression and anxiety questionnaires, seven visual analog scales of subjective feelings (memory, digestion, etc.), and physical performance.

Results

At baseline, the probiotic-placebo group A (n = 40, age 69 ± 7 years, education 16 ± 3 years, 63% females, body mass index 28.5 ± 6, subjective memory complaint in 43%) did not differ from the placebo-probiotic group B (n = 32) in any of the sociodemographic characteristics and evaluated measures including cognitive status. At follow-up visits after 3, 6, and 8  months, no cross-sectional differences in any of the measures were found between the groups except worse sentence recall of the ALBA test after 3  months of probiotic use. Score changes were not observed for all cognitive tests but one in any group between visits 1 and 3 and between visits 3 and 6. The only change was observed for the TMT B test after the first three months but no change was observed after the second three months.

Conclusion

The treatment with human probiotics and prebiotics did not improve cognitive, affective, or physical measures in community-dwelling individuals with normal or mildly impaired cognitive functions.

Clinical trial registration

clinicaltrials.gov, identifier NCT05051501.

Impact of probiotics on cognition and constipation in the elderly: A meta-analysis

Cognitive decline and constipation are common complications in the elderly. Probiotics are potential therapeutic agents to ameliorate cognitive impairment through gut-brain axis. Several clinical studies have investigated the beneficial effects of probiotics on cognitive impairment and constipation in elderly. However, a quantitative meta-analysis is required to evaluate the efficacy of probiotics on cognitive function and constipation. Thirteen clinical studies were included in this meta-analysis. We examined the risk of bias assessment and heterogeneity of eight studies for cognition and five studies for constipation, followed by group and subgroup meta-analyses using a random-effects model to evaluate the potential of probiotic supplements on cognition function and constipation in aged people. The results of the pooled meta-analysis revealed that probiotic supplementation did not improve the cognitive rating scale assessment for all studies (estimate = 0.13; 95%CI [-0.18, 0.43]; p = 0.41; I2 = 83.51%). However, subgroup analysis of single strain supplementation showed improved cognitive function in elderly people (estimate = 0.35; 95%CI [0.02, 0.69]; p = 0.039; I2 = 19.19%) compared to multiple strains. Probiotics also enhanced defecation frequency in constipated patients (estimate = 0.27; 95%CI [0.05, 0.5]; p = 0.019; I2 = 67.37%). Furthermore, probiotic supplementation resulted in higher fecal Lactobacillus counts than placebo (estimate = 0.37; 95%CI [0.05, 0.69]; p = 0.026; I2 = 21.3%). Subgroup analysis indicated that a probiotic intervention period of ≥4 weeks was more effective (estimate = 0.35; 95%CI [0.01, 0.68]; p = 0.044; I2 = 0%) in reducing constipation symptoms than a short intervention duration. Based on these results, probiotic supplementation could be a potential intervention to reduce constipation symptoms in the elderly population. The heterogeneity between studies is high, and limited trials are available to evaluate the cognitive function of aged individuals using probiotics. Therefore, further studies are required to determine the effect of probiotics on cognition.

Effects of exercise and physical activity on gut microbiota composition and function in older adults: a systematic review

BACKGROUND

The characterization and research around the gut microbiome in older people emphasize microbial populations change considerably by losing the diversity of species. Then, this review aims to determine if there is any effect on the gut microbiota of adults older than 65 that starts an exercise intervention or improves physical activity level. Also, this review describes the changes in composition, diversity, and function of the gut microbiota of older subjects that had improved their physical activity level.

METHODS

The type of studies included in this review were studies describing human gut microbiota responses to any exercise stimulus; cross-sectional studies focused on comparing gut microbiota in older adults with different physical activity levels-from athletes to inactive individuals; studies containing older people (women and men), and studies written in English. This review's primary outcomes of interest were gut microbiota abundance and diversity.

RESULTS

Twelve cross-sectional studies and three randomized controlled trials were examined. Independently of the type of study, diversity metrics from Alpha and Beta diversity remained without changes in almost all the studies. Likewise, cross-sectional studies do not reflect significant changes in gut microbiota diversity; no significant differences were detected among diverse groups in the relative abundances of the major phyla or alpha diversity measures. Otherwise, relative abundance analysis showed a significant change in older adults who conducted an exercise program for five weeks or more at the genus level.

CONCLUSIONS

Here, we did not identify significant shifts in diversity metrics; only one study reported a significant difference in Alpha diversity from overweight people with higher physical activity levels. The abundance of some bacteria is higher in aged people, after an exercise program, or in comparison with control groups, especially at the genus and species levels. There needs to be more information related to function and metabolic pathways that can be crucial to understand the effect of exercise and physical activity in older adults.

TRIAL REGISTRATION

PROSPERO ID: CRD42022331551.

Probiotic supplementation improved cognitive function in cognitively impaired and healthy older adults: a systematic review of recent trials

INTRODUCTION

Recent evidence suggests that there is clear association between microbiota and cognitive functioning, which is known as microbiome-gut-brain axis. Probiotic bacteria consumption can alter human microbiota; therefore, probiotic supplementation might affect the gut microbiota dynamics and influence cognitive function.

METHODS

Three electronic databases including PubMed, ProQuest, and EBSCOHost databases were utilized. Manual hand search of article was also done. We selected randomized controlled trial articles that measure cognitive function (as the primary outcome) after intervention with probiotic supplementation on older adult population with AD, MCI, or healthy condition. The following terms and its variant were used: "probiotic," "cognitive function," "mild cognitive impairment," "dementia," and "Alzheimer's disease."

RESULT

Nine of 10 included studies (AD, MCI, or healthy cognition population) showed cognitive function was improved significantly after probiotic supplementation, compared to control group. One study that included severe AD did not show significant changes.

CONCLUSION

Most studies involving AD, MCI, or healthy older adults showed cognitive improvement in subjects treated with probiotics for 12-24 weeks.

The Therapeutic Impact of Plant-Based and Nutritional Supplements on Anxiety, Depressive Symptoms and Sleep Quality among Adults and Elderly: A Systematic Review of the Literature

BACKGROUND

The emerging research in the literature continues to forecast a drastic and alarming increase in negative mental health and sleep health outcomes among populations, especially after the COVID-19 pandemic, which significantly influenced people's way of life. With mental health pharmaceutical interventions continuing to be stigmatized and inaccessible among populations, natural supplements provide an opportunity for intervention.

OBJECTIVE

This study sought to conduct a systematic review of the literature on the most recent comprehensive evidence for which nutritional supplements have the greatest therapeutic impact on symptoms of anxiety, depression, and insomnia.

METHODS

A systematic search of the literature, utilizing several databases, including PubMed and Web of Science, was conducted on 29 April 2022. We used developed keywords and MeSH terms for the search. The study eligibility criteria included (1) a randomized control trial; (2) investigating a plant-based therapeutic or natural supplement as the intervention; (3) measuring at least one health outcome of the following: anxiety symptoms, depressive symptoms, or sleep health outcomes; (4) utilizing validated measurement tools to measure the outcome of interest; (5) written in the English language; (6) peer reviewed; and (7) focused on adults and elderly populations.

MAIN RESULTS

Following the PRISMA guidelines, 76 studies were included in this review. We used the revised Risk of Bias tool (RoB2) to assess the quality of all included randomized control trials. A qualitative data synthesis was conducted. Overall, we found several valuable insights from the evidence in the literature, including evidence that demonstrates the benefits of probiotics and vitamin B complexes on anxiety symptoms, depressive symptoms, and sleep quality. Implication of Key Findings: This review provides the most updated findings in the literature on the topic, including an abundance of research that was published in the past 5 years. Given the expected rise in negative mental and sleep health outcomes following the pandemic, the supplements and therapeutics identified in this study should be the target of intervention measures to increase their accessibility and affordability and allow them to be incorporated into clinical guidelines of treatment. PROSPERO registration number: CRD42022361130.

Impact of probiotics on muscle mass, muscle strength and lean mass: a systematic review and meta-analysis of randomized controlled trials

Probiotics have shown potential to counteract sarcopenia, although the extent to which they can influence domains of sarcopenia such as muscle mass and strength in humans is unclear. The aim of this systematic review and meta-analysis was to explore the impact of probiotic supplementation on muscle mass, total lean mass and muscle strength in human adults. A literature search of randomized controlled trials (RCTs) was conducted through PubMed, Scopus, Web of Science and Cochrane Library from inception until June 2022. Eligible RCTs compared the effect of probiotic supplementation versus placebo on muscle and total lean mass and global muscle strength (composite score of all muscle strength outcomes) in adults (>18 years). To evaluate the differences between groups, a meta-analysis was conducted using the random effects inverse-variance model by utilizing standardized mean differences. Twenty-four studies were included in the systematic review and meta-analysis exploring the effects of probiotics on muscle mass, total lean mass and global muscle strength. Our main analysis (k = 10) revealed that muscle mass was improved following probiotics compared with placebo (SMD: 0.42, 95% CI: 0.10-0.74, I²  = 57%, P = 0.009), although no changes were revealed in relation to total lean mass (k = 12; SMD: -0.03, 95% CI: -0.19 - 0.13, I²  = 0%, P = 0.69). Interestingly, a significant increase in global muscle strength was also observed among six RCTs (SMD: 0.69, 95% CI: 0.33-1.06, I²  = 64%, P = 0.0002). Probiotic supplementation enhances both muscle mass and global muscle strength; however, no beneficial effects were observed in total lean mass. Investigating the physiological mechanisms underpinning different ageing groups and elucidating appropriate probiotic strains for optimal gains in muscle mass and strength are warranted.

Efficacy of Bifidobacterium longum alone or in multi-strain probiotic formulations during early life and beyond

The significance of Bifidobacterium to human health can be appreciated from its early colonization of the neonatal gut, where Bifidobacterium longum represents the most abundant species. While its relative abundance declines with age, it is further reduced in several diseases. Research into the beneficial properties of B. longum has unveiled a range of mechanisms, including the production of bioactive molecules, such as short-chain fatty acids, polysaccharides, and serine protease inhibitors. From its intestinal niche, B. longum can have far-reaching effects in the body influencing immune responses in the lungs and even skin, as well as influencing brain activity. In this review, we present the biological and clinical impacts of this species on a range of human conditions beginning in neonatal life and beyond. The available scientific evidence reveals a strong rationale for continued research and further clinical trials that investigate the ability of B. longum to treat or prevent a range of diseases across the human lifespan.

Randomised controlled trials for the prevention of cognitive decline or dementia: A systematic review

Dementia prevention research has progressed rapidly in recent years, with publication of several large lifestyle intervention trials, and renewed interest in pharmacological interventions, notably for individuals with Alzheimer's disease biomarkers, warranting an updated review of results and methodology. We identified 112 completed trials testing the efficacy of single-domain pharmacological (n = 33, 29%), nutritional (n = 27, 24%), physical activity (n = 18, 16%) and cognitive stimulation (n = 13, 12%), or multidomain (n = 22, 20%) interventions on incident dementia, or a relevant intermediate marker (e.g. cognitive function, biomarkers or dementia risk scores) in people without dementia. The earliest trials tested pharmacological interventions or nutritional supplements, but lifestyle interventions predominated in the last decade. In total, 21 (19%) trials demonstrated a clear beneficial effect on the pre-specified primary outcome (or all co-primary outcomes), but only two (10%) were large-scale (testing blood pressure lowering (Syst-Eur) or multidomain (FINGER) interventions on incident dementia and cognitive change in cognitive function, respectively). Of the 116 ongoing trials, 40% (n = 46) are testing multidomain interventions. Recent methodological shifts concern target populations, primary outcome measures, and intervention design, but study design remains constant (parallel group randomised controlled trial). Future trials may consider using adaptive trials or interventions, and more targeted approaches, since certain interventions may be more effective in certain subgroups of the population, and at specific times in the life-course. Efforts should also be made to increase the representativeness and diversity of prevention trial populations.

Can probiotics mitigate age-related neuroinflammation leading to improved cognitive outcomes?

Changes in brain structure and cognitive function are a natural part of aging; however, in some cases these changes are more severe resulting in mild cognitive impairment (MCI) or Alzheimer's disease (AD). Evidence is mounting to show that neuroinflammation is an underlying risk factor for neurodegenerative disease progression. Age-related neuroinflammation does not appear to occur in isolation and is part of increased systemic inflammation, which may in turn be triggered by changes in the gut associated with aging. These include an increase in gut permeability, which allows immune triggering compounds into the body, and alterations in gut microbiota composition leading to dysbiosis. It therefore follows that, treatments that can maintain healthy gut function may reduce inflammation and protect against, or improve, symptoms of age-associated neurodegeneration. The aim of this mini review was to evaluate whether probiotics could be used for this purpose. The analysis concluded that there is preliminary evidence to suggest that specific probiotics may improve cognitive function, particularly in those with MCI; however, this is not yet convincing and larger, multilocation, studies focus on the effects of probiotics alone are required. In addition, studies that combine assessment of cognition alongside analysis of inflammatory biomarkers and gut function are needed. Immense gains could be made to the quality of life of the aging population should the hypothesis be proven to be correct.

Effects of probiotic supplementation on cognitive function in elderly: A systematic review and Meta-analysis

OBJECTIVES

Probiotic supplementation has been linked to changes in cognitive function via the gut-brain axis (GBA). However, the current literature lacks a comprehensive review regarding this matter in the elderly population.

METHOD

Electronic databases including Medline (PubMed), Scopus, Embase, Web of Science, and Google Scholar were comprehensively searched for identifying studies that assessed the effects of probiotics on the cognitive function of the elderly published until July 2020. Articles were critically reviewed and if met the inclusion criteria, entered the study.

RESULTS

Among a total of 1374 studies, 10 were eligible for meta-analysis. No significant alteration was found in the cognition of the elderly (SMD=-0.04; 95% CI [- 1.07,0.98]; P = 0.93). There was a nonsignificant increase in the level of brain-derived neurotrophic factor (SMD = 0.58; 95% CI [-1.40,2.56]; P = 0.56) and a nonsignificant reduction in malondialdehyde levels (SMD=-0.44; 95% CI [-1.07,0.19]; P = 0.17). Levels of total antioxidant capacity (SMD = 39.93; 95% CI [2.92,76.95]; P = 0.03) and total glutathione (SMD = 61.51; 95% CI [12.39,110.62]; P = 0.01) significantly increased. A significant reduction was also noted in total cholesterol levels (SMD=-4.23; 95% CI [-8.32, -0.14]; P = 0.04).

CONCLUSION

Our study did not support the hypothesis of the positive effect of probiotics on cognitive function in the elderly population; which might be due to the heterogeneity across the studies.

Nutritional status in female patients with nontuberculous mycobacterial lung disease and its association with disease severity

Background

In women, slender body habitus has been reported to be one of the predisposing factors underlying the development and poor prognosis of non-tuberculous mycobacterial lung disease (NTM-LD). Given the lack of nutritional data contributing to treatment strategies, we aimed to clarify the nutritional status of female patients with NTM-LD and its association with disease severity.

Methods

In this single-center observational study, we enrolled 81 female outpatients with NTM-LD. Data on healthy women of similar ages were selected from our previous survey data and categorized as controls. First, we compared anthropometric and dietary survey data between patients and controls. Second, after the patients were categorized into relatively mild (mild, n = 40) and relatively severe groups (severe, n = 41) based on pulmonary X-ray-image finding scores, body composition, nutritional intake, and biochemical markers were compared between the groups. To identify nutritional factors associated with disease severity, logistic regression analyses were performed.

Results

Compared with controls, patients with NTM-LD had significantly lower energy intake, body mass index, body fat, and skeletal muscle mass (all p < 0.001). Compared with the mild group, the severe group had significantly lower skeletal muscle mass (p = 0.037), albumin (p = 0.029), transthyretin (prealbumin) (p = 0.002), retinol-binding protein (p = 0.011), and hemoglobin (p = 0.001); however, no between-group differences were observed in energy or nutrient intake. Logistic analyses revealed that transthyretin (p = 0.025) and hemoglobin (p = 0.003) levels were independent factors associated with disease severity.

Conclusions

This is the first study to comprehensively report the association between NTM-LD severity and nutritional status, including body composition, nutrient intake, and biomarkers. The results suggest that initiating nutritional therapy from the mild stage of the disease to prevent undernutrition is warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-02109-5.

Dietary Fiber Intake is Associated with Cognitive Function in Older Adults: Data from the National Health and Nutrition Examination Survey

BACKGROUND

Aging is a global health challenge that is associated with a decline in cognitive function. In the United States, most older adults (≥50 years) do not meet the recommended daily fiber intake, although preliminary evidence suggests that dietary fiber consumption could elicit clinical benefits on cognitive function. We investigated the associations between dietary fiber intake and cognitive function in older adults.

METHODS

We analyzed data from the US National Health and Nutrition Examination Survey (NHANES) between 2011 and 2014, with a study cohort of 1070 older adults (≥60 years). Cognitive function was assessed using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word Learning Test (WLT), Word Recall Test (WRT) and their Intrusion Word Count Tests (WLT-IC and WRT-IC), the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST). Multiple linear regression and cubic spline analyses were employed to examine the association between dietary fiber intake and cognitive performance on a test-by-test basis, after covariates adjustment (ie, age, sex, race, socioeconomic status, educational level, medical history, body mass index, alcohol, and energy intake).

RESULTS

Participants had a mean age of 69.2 years and were primarily non-Hispanic white of middle-high socioeconomic status with a college degree at minimum. The mean dietary fiber intake was 17.3 g/d. The analysis showed that dietary fiber intake was positively associated with DSST (P = .031). No associations with CERAD WLT (P = .41), WRT (P = .68), WLT-IC (P = .07), and WRT-IC (P = .28), and AFT (P = .40) scores were observed. A plateau in DSST score was revealed at a dietary fiber intake of 34 g/d.

CONCLUSIONS

Higher dietary fiber intake is associated with improved specific components of cognitive function in older adults aged 60 years and older. Public health interventions that target a recommended dietary fiber intake may provide a promising strategy to combat cognitive decline in high-risk groups of older adults.

Gut microbiota in sarcopenia and heart failure

Sarcopenia is common in aging and in patients with heart failure (HF) who may experience worse outcomes. Patients with muscle wasting are more likely to experience falls and can have serious complications when undergoing cardiac procedures. While intensive nutritional support and exercise rehabilitation can help reverse some of these changes, they are often under-prescribed in a timely manner, and we have limited insights into who would benefit. Mechanistic links between gut microbial metabolites (GMM) have been identified and may contribute to adverse clinical outcomes in patients with cardio-renal diseases and aging. This review will examine the emerging evidence for the influence of the gut microbiome-derived metabolites and notable signaling pathways involved in both sarcopenia and HF, especially those linked to dietary intake and mitochondrial metabolism. This provides a unique opportunity to gain mechanistic and clinical insights into developing novel therapeutic strategies that target these GMM pathways or through tailored nutritional modulation to prevent progressive muscle wasting in elderly patients with heart failure.

Examining the cognitive benefits of probiotic supplementation in physically active older adults: A randomized clinical trial

The prevalence of dementia is projected to increase with the growing older adult population and prevention strategies are urgently needed. Two promising interventions include physical activity (PA) and probiotic supplementation, with initial findings suggesting their combined use may confer greater cognitive benefits than either intervention alone. However, no study has yet examined the effects of probiotic supplementation on cognitive function in healthy, physically active older adults. The present study used archival data from a randomized clinical trial including 127 physically active, middle-aged to older adults (avg age 64.3 years) with self-reported PA levels meeting or exceeding recommendations to investigate the effects of probiotic supplementation (Lactobacillus rhamnosus GG; L.GG) on cognitive outcomes. Repeated measures ANOVAs showed no significant changes in cognitive performance from baseline to follow up as an effect of L.GG consumption. These results suggest that probiotic supplementation may not improve cognitive function in persons already engaged in high levels of PA. Future research should include prospective studies to determine whether long-term use of probiotic supplementation may help prevent cognitive decline. Novelty: • Initial research shows promising cognitive benefits of combined physical activity and probiotics consumption. • L.GG did not lead to acute cognitive improvements for older adults already meeting physical activity guidelines. • Prospective studies examining prevention of cognitive decline with probiotics in healthy and clinical samples are much needed.

Dietary Supplementations and Depression

Depression is a mood disturbance condition that occurs for more than two weeks in a row, leading to suicide. Due to adverse effects of depression, antidepressants and adjunctive therapies, such as dietary supplementation, are used for treatment. Therefore, this review explored and summarized dietary supplements’ types, dosages, and effectiveness in preventing and treating depression. A literature search of the PubMed database was conducted in August 2021 to identify studies assessing depression, after which scale measurements based on dietary supplements were identified. From the obtained 221 studies, we selected 63 papers. Results showed PUFA (EPA and DHA combination), vitamin D, and probiotics as the most common supplementation used in clinical studies to reduce depressive symptoms. We also observed that although the total daily PUFA dosage that exhibited beneficial effects was in the range of 0.7–2 g EPA and 0.4–0.8 g DHA daily, with an administration period of three weeks to four months, positive vitamin D-based supplementation effects were observed after administering doses of 2000 IU/day or 50,000 IU/week between 8 weeks and 24 months. Alternatively, microbes from the genus Lactobacillus and Bifidobacterium in the probiotic group with a minimum dose of 10⁸ CFU in various dose forms effectively treated depression. Besides, a depression scale was helpful to assess the effect of an intervention on depression. Hence, PUFA, vitamin D, and probiotics were proposed as adjunctive therapies for depression treatment based on the results from this study.

Optimal dose and type of exercise to improve cognitive function in older adults: A systematic review and bayesian model-based network meta-analysis of RCTs

OBJECTIVE

To examine the dose-response relationship between overall and specific types of exercise with cognitive function in older adults.

DESIGN

Systematic Review and Bayesian Model-Based Network Meta-Analysis.

DATA SOURCES

Systematic search of MEDLINE, Web of Science, Scopus, PsycINFO and SPORTDiscus.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomized controlled trials of exercise interventions in participants aged 50 years or over, and that reported on at least one global cognition outcome.

RESULTS

The search returned 1998 records, of which 44 studies (4793 participants; 102 different effect sizes) were included in this review with meta-analysis. There was a non-linear, dose-response association between overall exercise and cognition. We found no minimal threshold for the beneficial effect of exercise on cognition. The estimated minimal exercise dose associated with clinically relevant changes in cognition was 724 METs-min per week, and doses beyond 1200 METs-min per week provided less clear benefits. We also found that the dose-response association was exercise type dependent, and our results show that clinically important effects may occur at lower doses for many types of exercise. Our findings also highlighted the superior effects of resistance exercises over other modalities.

CONCLUSIONS

If provided with the most potent modalities, older adults can get clinical meaningful benefits with lower doses than the WHO guidelines. Findings support the WHO recommendations to emphasise resistance training as a critical component of interventions for older adults.

Increased physical activity improves gut microbiota composition and reduces short-chain fatty acid concentrations in older adults with insomnia

Physical activity (PA) can improve functional abilities, well-being, and independence in older adults with insomnia. Studies have shown that PA may be linked to changes in the gut microbiota composition and its metabolites' concentrations. This association among older adults with insomnia, however, is yet to be determined. We explored the relationships between physical activity (PA) levels, gut microbiota composition, and short-chain fatty acid (SCFA) levels in this population. Forty-nine community-dwelling adults with insomnia symptoms, aged 65 and older, participated in this study. Their average daily step-count and sleep continuity measures over a two-week period were calculated based on Actigraphic recordings. Each participant provided fecal samples for the microbiome and SCFA analyses, anthropometric measures, and information via questionnaires on medical history and food consumption. The gut microbiota composition and SCFA concentrations were determined by next-generation sequencing and Gas chromatography-mass spectrometry, respectively. Participants were divided into two groups (more and less active) according to their median step/day count. We compared the microbiota abundance and SCFA concentrations between groups and performed correlation analysis between gut microbiota abundances and study variables. Different microbiota taxa in each PA group and increased SCFAs in feces of less active individuals were found. Changes in step counts were positively or negatively associated with the relative abundance of 19 ASVs, 3 microorganisms at the family level, and 11 microorganisms at the genus level. Furthermore, significant associations were discovered among physical activity, gut microbiota, SCFAs, and sleep parameters. Our findings provide new insights on the relationship between PA, gut microbiota composition, and primary metabolites in older adults with insomnia.

Effect of Probiotics on Psychiatric Symptoms and Central Nervous System Functions in Human Health and Disease: A Systematic Review and Meta-Analysis

Background: The gut microbiota impacts on central nervous system (CNS) function via the microbiota–gut–brain axis. Thus, therapeutics targeting the gut microbiota such as probiotics have the potential for improving mental health. This meta-analysis synthesizes the evidence regarding the impacts of probiotics on psychological well-being, psychiatric symptoms and CNS functioning. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were applied for executing this review using the databases PubMed, Web of Science and Cochrane Library. The data were summarized at qualitative and quantitative level. Results: Fifty-four randomized placebo-controlled studies were included, of which 30 were eligible for meta-analysis. If investigated, the probiotics mostly exerted effects on CNS function. Most probiotics did not affect mood, stress, anxiety, depression and psychiatric distress when compared to placebo at the qualitative level. At quantitative level, depression and psychiatric distress improved slightly in the probiotic condition (depression: mean difference −0.37 (95% CI: −0.55, −0.20); p ≤ 0.0001; psychiatric distress: mean difference −0.33 (95% CI: −0.53, −0.13); p = 0.001). Conclusions: To date it is unclear to which extent and in which specific areas next generation probiotics selected and developed for their ability to improve psychiatric condition and potentially other CNS functions are promising.

Probiotic supplementation demonstrates therapeutic potential in treating gut dysbiosis and improving neurocognitive function in age-related dementia

PURPOSE

Probiotics, as live microorganisms that improve intestinal microbial balance, have been implicated in the modulation of neurodegenerative diseases via the microbiome-gut-brain axis by improving gut dysbiosis. This review examines the association between probiotics and neurocognitive function in age-related dementia.

METHODS

We searched MEDLINE, Embase, Scopus, Web of Science and Cochrane library for in vivo studies using equivalent combinations of "probiotics" and "dementia" as per PRISMA. From the 52 in vivo studies identified, 5 human and 22 animal studies with comparable quantitative outcomes on neurocognitive/behavioural function were meta-analysed by forest plots, subgroup analysis and meta-regression. The analysis of biomarkers, risk of bias and publication bias were also performed.

RESULTS

In elderly humans, probiotics correlates with a non-significant difference of neurocognitive function in Mini-Mental State Examination, but with significant improvement only in those diagnosed with Alzheimer's disease. In animals, probiotics significantly improved neurocognitive function as measured by Morris Water Maze, Y-Maze, and Passive Avoidance. Further analysis by subgrouping and meta-regression found that the probiotics-neurodegeneration association is age dependent in humans but is neither dose dependent nor duration dependent in animals or humans. Analysis of biomarkers suggested that the neurocognitive effect of probiotics is associated with an altered gut microbiome profile, downregulated proteinopathic, inflammatory and autophagic pathways, and upregulated anti-oxidative, neurotrophic, and cholinergic pathways.

CONCLUSION

Overall, we report promising results in animal studies but limited evidence of probiotics leading to neurocognitive improvement in humans. More research into probiotics should be conducted, especially on live biotherapeutic products for targeted treatment of gut dysbiosis and age-related dementia.

Effectiveness and safety of Bifidobacterium in preventing dental caries: a systematic review and meta-analysis

OBJECTIVES

The effectiveness and safety of Bifidobacterium in dental caries prevention are controversial. Thus, we performed this systematic review and meta-analysis to explore the preventive value of Bifidobacterium.

METHODS

Eligible studies were identified from several databases, including PubMed, the Cochrane Library, Embase, Web of Science, and Scopus. Hand searches were also conducted in relevant bibliographies. We then extracted and pooled standardized mean difference (SMD) and risk ratio (RR) to analyze the anti-caries effect of Bifidobacterium with Stata 16.0 software. If the data obtained was not suitable for meta-analysis, qualitative descriptions were performed.

RESULTS

Compared with the placebo control group, there was no statistically significant reduction in Streptococcus mutans and Lactobacilli counts in saliva in the test group. Also, there were no significant differences in Streptococcus mutans and Lactobacillus counts in dental plaque and no significant difference in caries incidence in deciduous teeth. There was no significant difference in the incidence of adverse events between the Bifidobacterium and control groups.

CONCLUSIONS

Available evidence demonstrates that Bifidobacterium is neither effective in reducing Streptococcus mutans and Lactobacillus counts in the saliva or dental plaque nor in reducing the occurrence of caries in deciduous teeth. Evaluation of its safety requires further investigations. Therefore, Bifidobacterium is not a competent probiotic candidate to prevent dental caries.

Microbiota shaping — the effects of probiotics, prebiotics, and fecal microbiota transplant on cognitive functions: A systematic review

BACKGROUND

Dementia is a chronic progressive neurological disease affecting millions of people worldwide, and represents a relevant economic burden for healthcare systems. Although its pathogenesis is still unknown, recent findings have reported that a dysregulated gut-brain axis communication, a fundamental relationship mediated by several host and microbial molecules, is associated with cognitive disorders. In addition, gut microbiota manipulation reduces neuroinflammation, improving cognitive function by restoring the functional gut-brain axis.

AIM

To better define the effects of probiotics, prebiotics, synbiotics, and fecal microbiota transplant (FMT) on cognitive function.

METHODS

We performed a literature search of human randomized clinical trials to examine the effects of the administration of probiotics, prebiotics, synbiotics, or FMT on cognition outcomes in healthy or sick people of every age, sex, and nationality. We systematically searched Embase, Medline/PubMed, Cochrane Library, central and clinicaltrials.gov databases with a combination of comprehensive terms related to cognition and gut microbiota manipulation. Then we carefully reviewed and synthesized the data by type of study design and setting, characteristics of the studied population, kind of intervention (strain type or mixture type, dosage, and frequency of administration), control treatment, inclusion and exclusion criteria, follow-up duration, and cognitive or memory outcomes.

RESULTS

After examining the titles and abstracts, the initial literature screening identified 995 articles, but we added 23 papers in our systematic review. The analyses of these selected studies highlighted that both probiotic supplementation and FMT improved cognitive function regardless of the type and posology of administration and the adopted cognitive tests and questionnaires. We found that most of the studies conducted in healthy people showed a significant positive effect of the intervention on at least one of the performed cognitive tests. Regarding unhealthy subjects, while FMT and especially probiotic administration had multiple beneficial effects on different cognitive functions, supplementation with prebiotics did not provide any cognitive improvement.

CONCLUSION

Probiotic supplementation and FMT may represent a promising strategy to restore gut eubiosis and enhance the cognitive functions of healthy people and patients with neurological disorders.

The diversity and composition of the human gut lactic acid bacteria and bifidobacterial microbiota vary depending on age

Aging is associated with gut microbiota alterations, characterized by changes in intestinal microbial diversity and composition. However, no study has yet focused on investigating age-related changes in the low-abundant but potentially beneficial subpopulations of gut lactic acid bacteria (LAB) and Bifidobacterium. Our study found that the subjects' age correlated negatively with the alpha diversity of the gut bifidobacterial microbiota, and such correlation was not observed in the gut LAB subpopulation. Principal coordinate analysis (PCoA) and analysis of distribution of operational taxonomic units (OTUs) revealed that the structure and composition of the gut bifidobacterial subpopulation of the longevous elderly group were rather different from that of the other three age groups. The same analyses were applied to identify age-dependent characteristics of the gut LAB subpopulation, and the results revealed that the gut LAB subpopulation of young adults was significantly different from that of all three elderly groups. Our study identified several potentially beneficial bacteria (e.g., Bifidobacterium breve and Bifidobacterium longum) that were enriched in the longevous elderly group (P < 0.05), and the relative abundance of Bifidobacterium adolescentis decreased significantly with the increase in age (P < 0.05). Although both bifidobacteria and LAB are generally considered as health-promoting taxa, their age-dependent distribution varied from each other, suggesting their different life stage changes and potentially different functional roles. This study provided novel species-level gut bifidobacterial and LAB microbiota profiles of a large cohort of subjects and identified several age-or longevity-associated features and biomarkers. KEY POINTS: • The alpha diversity of the gut bifidobacterial microbiota decreased with age, while LAB did not change. • The structure and composition of the gut bifidobacterial subpopulation of the longevous elderly group were rather different from that of the other three age groups. • Several potentially beneficial bacteria (e.g., Bifidobacterium breve and Bifidobacterium longum) that were enriched in the longevous elderly group.

The effect of interventions targeting gut microbiota on depressive symptoms: a systematic review and meta-analysis

BACKGROUND

Despite their popularity, the efficacy of interventions targeting gut microbiota to improve depressive symptoms is unknown. Our objective is to summarize the effect of microbiome-targeting interventions on depressive symptoms.

METHODS

We conducted a systematic review and meta-analysis. We searched MEDLINE, Embase, PsycINFO, Database of Abstracts of Reviews of Effects, Cochrane Database of Systematic Reviews and the Cochrane Controlled Register of Trials from inception to Mar. 5, 2021. We included studies that evaluated probiotic, prebiotic, synbiotic, paraprobiotic or fecal microbiota transplant interventions in an adult population (age ≥ 18 yr) with an inactive or placebo comparator (defined by the absence of active intervention). Studies must have measured depressive symptoms with a validated scale, and used a randomized controlled trial study design. We conducted a random effects meta-analysis of change scores, using standardized mean difference as the measure of effect.

RESULTS

Sixty-two studies formed the final data set, with 50 included in the meta-analysis. Probiotic, prebiotic, and synbiotic interventions on depressive symptoms showed statistically significant benefits. In the single studies evaluating each of fecal microbiota transplant and paraprobiotic interventions, neither showed a statistically significant benefit.

INTERPRETATION

Despite promising findings of benefit of probiotic, prebiotic and synbiotic interventions for depressive symptoms in study populations, there is not yet strong enough evidence to favour inclusion of these interventions in treatment guidelines for depression. Critical questions about species administered, dosage and timing relative to other antidepressant medications remain to be answered.

STUDY REGISTRATION

PROSPERO no. 143178.

Gut Microbiota, Probiotic Interventions, and Cognitive Function in the Elderly: A Review of Current Knowledge

Changes in the composition and proportions of the gut microbiota may be associated with numerous diseases, including cognitive impairment. Over the recent years, the growing interest in this relation is observed, but there are still many unknowns, especially in the elderly. To the best of our knowledge, this is the first work that synthesizes and critically evaluates existing evidence on the possible association between human gut microbiota and cognitive function in the elderly. For this purpose, comprehensive literature searches were conducted using the electronic databases PubMed, Google Scholar, and ScienceDirect. The gut microbiota of cognitively healthy and impaired elderly people may differ in the diversity and abundance of individual taxes, but specific taxes cannot be identified. However, some tendencies to changing the Firmicutes/Bacteroidetes ratio can be identified. Currently, clinical trials involving probiotics, prebiotics, and synbiotics supplementation have shown that there are premises for the claim that these factors can improve cognitive functions, however there is no single intervention beneficial to the elderly population. More reliable evidence from large-scale, long-period RCT is needed. Despite proposing several potential mechanisms of the gut microbiota's influence on the cognitive function impairment, prospective research on this topic is extremely difficult to conduct due to numerous confounding factors that may affect the gut microbiota. Heterogeneity of research outcomes impairs insight into these relations.

The effect of probiotics on cognitive function across the human lifespan: A systematic review

Recently the scientific community has seen a growing interest in the role of the gut-brain axis and, in particular, how probiotic supplementation may influence neural function and behaviour via manipulation of the gut microbiota. The purpose of this review was to systematically review the current literature exploring the effect of probiotic intervention on cognitive function. PsychINFO, Web of Science, PubMed and Google Scholar were searched for human trials. Studies selected for inclusion administered a probiotic intervention and included at least one behavioural measure of cognitive performance. A total of 30 experimental papers were included, exploring the effect of probiotics across a variety of ages, populations and cognitive domains. The evidence suggests there may be potential for probiotics to enhance cognitive function or attenuate cognitive decline, particularly in clinically relevant adult populations for whom cognitive dysfunction may be present. However, the limited number of studies and the quality of the existing research makes it challenging to interpret the data. Further research is clearly warranted. PROSPERO: CRD42020164820.

The Effect of Probiotics on Health Outcomes in the Elderly: A Systematic Review of Randomized, Placebo-Controlled Studies

Increasing evidence suggests that probiotic supplementation may be efficacious in counteracting age-related shifts in gut microbiota composition and diversity, thereby impacting health outcomes and promoting healthy aging. However, randomized controlled trials (RCTs) with probiotics in healthy older adults have utilized a wide variety of strains and focused on several different outcomes with conflicting results. Therefore, a systematic review was conducted to determine which outcomes have been investigated in randomized controlled trials with probiotic supplementation in healthy older adults and what has been the effect of these interventions. For inclusion, studies reporting on randomized controlled trials with probiotic and synbiotic supplements in healthy older adults (defined as minimum age of 60 years) were considered. Studies reporting clinical trials in specific patient groups or unhealthy participants were excluded. In addition to assessment of eligibility and data extraction, each study was examined for risk of bias and quality assessment was performed by two independent reviewers. Due to the heterogeneity of outcomes, strains, study design, duration, and methodology, we did not perform any meta-analyses and instead provided a narrative overview of the outcomes examined. Of 1997 potentially eligible publications, 17 studies were included in this review. The risk of bias was low, although several studies failed to adequately describe random sequence generation, allocation concealment, and blinding. The overall study quality was high; however, many studies did not include sample calculations, and the majority of studies had a small sample size. The main outcomes examined in the trials included microbiota composition, immune-related measurements, digestive health, general well-being, cognitive function, and lipid and other biomarkers. The most commonly assessed outcome with the most consistent effect was microbiota composition; all but one study with this outcome showed significant effects on gut microbiota composition in healthy older adults. Overall, probiotic supplementation had modest effects on markers of humoral immunity, immune cell population levels and activity, as well as the incidence and duration of the common cold and other infections with some conflicting results. Digestive health, general-well-being, cognitive function, and lipid and other biomarkers were investigated in a very small number of studies; therefore, the impact on these outcomes remains inconclusive. Probiotics appear to be efficacious in modifying gut microbiota composition in healthy older adults and have moderate effects on immune function. However, the effect of probiotic supplementation on other health outcomes remains inconclusive, highlighting the need for more well-designed, sufficiently-powered studies to investigate if and the mechanisms by which probiotics impact healthy aging.

The Effect of Multiprobiotics on Memory and Attention in Fibromyalgia: A Pilot Randomized Controlled Trial

Fibromyalgia syndrome (FMS) is a chronic, generalized and diffuse pain disorder accompanied by cognitive deficits such as forgetfulness, concentration difficulties, loss of vocabulary and mental slowness, among others. In recent years, FMS has been associated with altered intestinal microbiota, suggesting that modulating gut microbiota (for example, through probiotics) could be an effective therapeutic treatment. Thus, the aim of the present study was to continue exploring the role of probiotics in cognitive processes in patients with FMS. A pilot randomized controlled trial was conducted in 31 patients diagnosed with FMS to compare the effects of a multispecies probiotic versus a placebo on cognitive variables (memory and attention) after eight weeks. Results showed that treatment with a multispecies probiotic produced an improvement in attention by reducing errors on an attention task, but it had no effect on memory. More specifically, a tendency to reduce errors of omission (Go trials) during the Go/No-Go Task was observed after treatment. These findings, along with our previous results in impulsivity, underline the relevance of using probiotics as a therapeutic option in FMS, although more research with a larger sample size is required.

Targeting the microbiome-gut-brain axis for improving cognition in schizophrenia and major mood disorders: A narrative review

Cognitive impairment has been consistently found to be a core feature of serious mental illnesses such as schizophrenia and major mood disorders (major depression and bipolar disorder). In recent years, a great effort has been made in elucidating the biological causes of cognitive deficits and the search for new biomarkers of cognition. Microbiome and gut-brain axis (MGB) hormones have been postulated to be potential biomarkers of cognition in serious mental illnesses. The main aim of this review was to synthesize current evidence on the association of microbiome and gut-brain hormones on cognitive processes in schizophrenia and major mood disorders and the association of MGB hormones with stress and the immune system. Our review underscores the role of the MGB axis on cognitive aspects of serious mental illnesses with the potential use of agents targeting the gut microbiota as cognitive enhancers. However, the current evidence for clinical trials focused on the MGB axis as cognitive enhancers in these clinical populations is scarce. Future clinical trials using probiotics, prebiotics, antibiotics, or faecal microbiota transplantation need to consider potential mechanistic pathways such as the HPA axis, the immune system, or gut-brain axis hormones involved in appetite control and energy homeostasis.

Role of Probiotics, Prebiotics, and Synbiotics in the Elderly: Insights Into Their Applications

Elderly people are an important part of the global population who suffer from the natural processes of senescence, which lead to changes in the gut microbiota composition. These modifications have a great impact on their quality of life, bringing a general putrefactive and inflammatory status as a consequence. Some of the most frequent conditions related to this status are constipation, undernutrition, neurodegenerative diseases, susceptibility to opportunistic pathogens, and metabolic disbalance, among others. For these reasons, there is an increasing interest in improving their quality of life by non-invasive treatments such as the consumption of probiotics, prebiotics, and synbiotics. The aim of the present mini-review is to describe the benefits of these functional supplements/food according to the most recent clinical and pre-clinical studies published during the last decade. In addition, insights into several aspects we consider relevant to improve the quality of future studies are provided.

Roles of Gut Microbiota in the Regulation of Hippocampal Plasticity, Inflammation, and Hippocampus-Dependent Behaviors

The study of the gut microbiota-brain axis has become an intriguing field, attracting attention from both gastroenterologists and neurobiologists. The hippocampus is the center of learning and memory, and plays a pivotal role in neurodegenerative diseases, such as Alzheimer’s disease (AD). Previous studies using diet administration, antibiotics, probiotics, prebiotics, germ-free mice, and fecal analysis of normal and specific pathogen-free animals have shown that the structure and function of the hippocampus are affected by the gut microbiota. Furthermore, hippocampal pathologies in AD are positively correlated with changes in specific microbiota. Genomic and neurochemical analyses revealed significant alterations in genes and amino acids in the hippocampus of AD subjects following a remarkable shift in the gut microbiota. In a recent study, when young animals were transplanted with fecal microbiota derived from AD patients, the recipients showed significant impairment of cognitive behaviors, AD pathologies, and changes in neuronal plasticity and cytokines. Other studies have demonstrated the side effects of antibiotic administration along with the beneficial effects of probiotics, prebiotics, and specific diets on the composition of the gut microbiota and hippocampal functions, but these have been mostly preliminary with unclear mechanisms. Since some specific gut bacteria are positively or negatively correlated to the structure and function of the hippocampus, it is expected that specific gut bacteria administration and other microbiota-based interventions could be potentially applied to prevent or treat hippocampus-based memory impairment and neuropsychiatric disorders such as AD.

Bifidobacterium animalis subsp. lactis BB-12 Improves the State Anxiety and Sports Performance of Young Divers Under Stress Situations: A Single-Arm, Prospective Proof-of-Concept Study

Background

Athletes will increase their state anxiety under stress situations, which will lead to the decline of sports performance. The improvement of anxiety by probiotics has been reported, but there is a lack of research in the athlete population. The purpose of the current study is to explore the effectiveness of probiotics in improving athletes' state anxiety and sports performance under stress situations.

Methods

We conducted this single-arm study in Chongqing Institute of Sports Technology. In the 8-week study, 21 Chongqing young divers (mean age: 9.10 ± 1.80) were given probiotic Bifidobacterium animalis subsp. lactis BB-12 (1 × 10⁹ colony-forming units/100 g) daily. The state anxiety and sports performance of athletes were measured before, during, and after the intervention, and the gut microbiota of athletes was measured before and after the intervention.

Results

The intervention results showed that cognitive state anxiety, somatic state anxiety, and anxiety emotion were improved (cognitive: Z = -3.964, P < 0.001; somatic: Z = -3.079, P = 0.003; anxiety: Z = -2.973, P < 0.001). In terms of gut microbiota, the intervention did not change the gut microbial composition (such as α diversity and β diversity) but increased the abundance of Bifidobacteriaceae. At the 8th week, the performance of athletes under stress was significantly improved (χ² = 7.88, P = 0.019).

Limitations

First of all, due to the restriction of the number of subjects in this study, there was no control group. Secondly, although the athletes' diet was recorded in this study, the influence of this factor on gut microbiota was not eliminated. Finally, the anxiety level of the athletes in this study was obtained through a self-report, lacking physiological data in state anxiety.

Conclusion

The results show that probiotics intervention can improve the state anxiety of athletes under stress situation and improve the performance of athletes under stress situation.

Nutritional Assessment in Older Adults : MNA® 25 years of a Screening Tool and a Reference Standard for Care and Research; What Next?

A tool to assess nutritional status in older persons was really needed. It took 5 years to design the MNA® (Mini Nutrition Assessment) tool, complete the first validations studies both in Europe and in the U.S. and to publish it. After the full MNA®, the MNA® short form and the self-MNA® have been validated. As well as Chinese and other national MNA® forms. Now more than 2000 clinical research have used the MNA® all over the world from community care to hospital. At least 22 Expert groups included the MNA® in new clinical practice guidelines, national or international registries. The MNA® is presently included in almost all geriatric and nutrition textbook and part of the teaching program for medicine and other health care professional worldwide. The urgent need is to target the frail older adults more likely to have weight loss and poor appetite and to prevent frailty and weight loss in the robust. We present in this paper the review of 25 years of clinical research and practice using the MNA® worldwide.

Associations between Pro- and Anti-Inflammatory Gastro-Intestinal Microbiota, Diet, and Cognitive Functioning in Dutch Healthy Older Adults: The NU-AGE Study

Dietary modulation of the gastro-intestinal microbiota is a potential target in improving healthy ageing and age-related functional outcomes, including cognitive decline. We explored the association between diet, gastro-intestinal microbiota and cognition in Dutch healthy older adults of the ‘New dietary strategies addressing the specific needs of the elderly population for healthy aging in Europe’ (NU-AGE) study. The microbiota profile of 452 fecal samples from 226 subjects was determined using a 16S ribosomal RNA gene-targeted microarray. Dietary intake was assessed by 7-day food records. Cognitive functioning was measured with an extensive cognitive test battery. We observed a dietary and microbial pro- to anti-inflammatory gradient associated with diets richer in animal- or plant-based foods. Fresh fruits, nuts, seeds and peanuts, red and processed meat and grain products were most strongly associated to microbiota composition. Plant-rich diets containing fresh fruits, nuts, seeds and peanuts were positively correlated with alpha-diversity, various taxa from the Bacteroidetes phylum and anti-inflammatory species, including those related to Faecalibacterium prausnitzii and Eubacterium rectale and E. biforme. Animal product-rich diets associated with pro-inflammatory species, including those related to Ruminococcus gnavus and Collinsella spp.. Cognition was neither associated with microbiota composition nor alpha-diversity. In conclusion, diets richer in animal- and plant-based foods were related to a pro- and anti-inflammatory microbial profile, while cognition was associated with neither.

Gerobiotics: probiotics targeting fundamental aging processes

Aging is recognized as a common risk factor for many chronic diseases and functional decline. The newly emerging field of geroscience is an interdisciplinary field that aims to understand the molecular and cellular mechanisms of aging. Several fundamental biological processes have been proposed as hallmarks of aging. The proposition of the geroscience hypothesis is that targeting holistically these highly integrated hallmarks could be an effective approach to preventing the pathogenesis of age-related diseases jointly, thereby improving the health span of most individuals. There is a growing awareness concerning the benefits of the prophylactic use of probiotics in maintaining health and improving quality of life in the elderly population. In view of the rapid progress in geroscience research, a new emphasis on geroscience-based probiotics is in high demand, and such probiotics require extensive preclinical and clinical research to support their functional efficacy. Here we propose a new term, “gerobiotics”, to define those probiotic strains and their derived postbiotics and para-probiotics that are able to beneficially attenuate the fundamental mechanisms of aging, reduce physiological aging processes, and thereby expand the health span of the host. We provide a thorough discussion of why the coining of a new term is warranted instead of just referring to these probiotics as anti-aging probiotics or with other similar terms. In this review, we highlight the needs and importance of the new field of gerobiotics, past and currently on-going research and development in the field, biomarkers for potential targets, and recommended steps for the development of gerobiotic products. Use of gerobiotics could be a promising intervention strategy to improve health span and longevity of humans in the future.