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

Exploring the acute and chronic effects of a multistrain probiotic supplement on cognitive function and mood in healthy older adults: a randomized controlled trial

BACKGROUND

Aging is associated with a decline in cognitive function and vulnerability to depression. Probiotic supplements have shown beneficial effects on cognition and mood in clinical populations, but the potential benefit for healthy older adults experiencing age-related decline in cognition remains unclear.

OBJECTIVES

The primary aim of the present work was to explore the effect of a chronic (long-term) multispecies probiotic intervention on cognition in healthy aging adults. Secondary aims included exploring the chronic effect on mood outcomes and gut microbiota community, as well as a novel investigation into the acute effect of supplementation on cognition and mood.

METHODS

The study employed a randomized, placebo-controlled, cross-over trial in 30 healthy older adults to explore the acute (1 d) and chronic (8 wk) effects of a probiotic supplement on cognitive domains of memory and executive function, alongside mood measures of stress, anxiety, depression, and cognitive reactivity to sad mood. 16s rRNA sequencing of stool samples was also performed pre- and postchronic intervention to assess potential effects on the gut microbiota.

RESULTS

Acute probiotic supplementation was associated with faster reaction times on cognitively demanding trials during a task of executive function [-64.91 ms, 95% confidence interval (CI): -115.70, -14.15]. Chronic supplementation was associated with improvement in cognitive biases such as hopelessness (-0.97, 95% CI: -1.72, -0.23), rumination (-1.58, 95% CI: -2.86, -0.29), and aggression (-1.57, 95% CI: -2.63, -0.51) that contribute to reactivity to sad mood and therefore vulnerability to depression, and may improve executive function under higher cognitive demand (0.43%, 95% CI: -0.53%, 1.38%).

CONCLUSIONS

The current work provides novel evidence for an acute effect of probiotics on reaction times during executive function, which should be replicated in future work. Additionally, this work replicates previous findings of improved cognitive reactivity to sad mood following chronic probiotic supplementation, indicating probiotics may reduce risk of developing depression in a healthy aging population. This study was registered at clinicaltrials.gov as NCT04951687.

Microbial signatures and therapeutic strategies in neurodegenerative diseases

Neurodegenerative diseases (NDs), including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS), arise from complex interactions between genetic factors, environmental exposures, and aging. Additionally, gut dysbiosis has been linked to systemic inflammation and neurodegeneration. Advances in microbiome and metabolome profiling techniques have provided deeper insights into how alterations in gut microbiota and dietary patterns affect metabolic pathways and contribute to the progression of NDs. This review explores the profiles of gut microbiome and metabolome derived biomarkers and their roles in NDs. Across phyla, families, and genera, we identified 55 microbial alterations in PD, 24 in AD, 4 in ALS, and 17 in MS. Some notable results include an increase in Akkermansia in PD, AD, and MS and a decrease in short-chain fatty acids (SCFAs) in PD and AD. We examined the effects of probiotics, prebiotics, fecal microbiota transplants (FMT), sleep, exercise, and diet on the microbiota, all of which contributed to delayed onset and alleviation of symptoms. Further, artificial intelligence (AI) and machine learning (ML) algorithms applied to omics data have been crucial in identifying novel therapeutic targets, diagnosing and predicting prognosis, and enabling personalized medicine using microbiota-modulating therapies in NDs patients.

Clinical significance of perioperative probiotic intervention on recovery following intestinal surgery

Restoring the balance of gut microbiota has emerged as a critical strategy in treating intestinal disorders, with probiotics playing a pivotal role in maintaining bacterial equilibrium. Surgical preparations, trauma, and digestive tract reconstruction associated with intestinal surgeries often disrupt the intestinal flora, prompting interest in the potential role of probiotics in postoperative recovery. Lan et al conducted a prospective randomized study on 60 patients with acute appendicitis, revealing that postoperative administration of Bacillus licheniformis capsules facilitated early resolution of inflammation and restoration of gastrointestinal motility, offering a novel therapeutic avenue for accelerated postoperative recovery. This editorial delves into the effects of perioperative probiotic supplementation on physical and intestinal recovery following surgery. Within the framework of enhanced recovery after surgery, the exploration of new probiotic supplementation strategies to mitigate surgical complications and reshape gut microbiota is particularly intriguing.

The Role of the Gut Microbiome and Probiotics in Sports Performance: A Narrative Review Update

Background/Objectives: Gut microbiome modulation through probiotics is a growing area of research, with several investigations reporting beneficial health outcomes for the host. Physical exercise has been shown to impact gut microbiome diversity. Emerging evidence suggests that probiotic supplementation can affect exercise performance. However, the mechanisms and domain-specific effects of gut microbiome modulation on performance remain to be elucidated. This narrative review aims to investigate the potential mechanisms underpinning the ergogenic benefits of probiotics and further define the current evidence base for specific performance domains. Discussion: The literature suggests that improved recovery after intense training regimes, enhanced nutrient absorption, alleviation of gastrointestinal symptoms, and improved immune function may underpin the beneficial effects of probiotics on sporting performance. A small number of trials also suggest that probiotic supplementation may improve symptoms of performance anxiety. However, further research is warranted on this topic. The evidence is most substantial for improvements in endurance performance, whilst only a few trials have investigated the impact upon power performance, albeit with promising results. Conclusions/Future Perspectives: In summary, probiotic supplementation has been shown to improve sporting performance; future research may wish to further explore the impact on power performance and investigate specific mechanisms of action.

Gut-Brain Axis and Brain Microbiome Interactions from a Medical Perspective

Background: The gut microbiome directly impacts brain health and activity, meaning the two are closely associated. This relationship suggests a link between microbial imbalances and diseases such as Alzheimer's, although multiple other contributing factors, such as genetics, also play a part. Additionally, recent studies discovered that cerebrospinal fluid has some microbial deoxyribonucleic acid (DNA), which can be interpreted to mean a microbiome exists in the brain too. The vagus nerve and the central nervous and immune systems are responsible for the connection between the brain and gut microbiome. Aims and Objectives: The main aim of this systematic review is to analyze existing research on the gut-brain axis and the brain microbiome to fill the current knowledge gap. Materials and Methods: A search was conducted on the PubMed database based on a set of predefined MeSH terms. Results: After the search, 2716 articles meeting the MeSH parameters were found in PubMed. This list was then downloaded and analyzed according to the inclusion/exclusion criteria, and 63 relevant papers were selected. Discussion: Bacteria in the gut microbiome produce some substances that are considered neuroactive. These compounds can directly or indirectly affect brain function through the gut-brain axis. However, various knowledge gaps on the mechanisms involved in this connection need to be addressed first.

Can microbiota gut-brain axis reverse neurodegenerative disorders in human?

The trillions of microbial populations residing in the gut have recently shown that they can be used as a remedy for various diseases. The gut microbiota-brain-axis interface is one unique pathway that the microbiota demonstrates its medicinal value. This medicinal value is further seen when there is a decline in gut microbial diversity (dysbiosis). Dysbiosis leads to neurodegenerative disorders (NDDs). The objective of this review is to ascertain the clinical significance of gut microbiota induced therapeutic strategies. While navigating this important area of interest, we will elucidate the research gaps, the prospects and the potential reverse interventions of the studied NDDs. In addition to our previous work, relevant literature published in English were searched and retrieved from the PubMed database. The 'gut microbiota and Neurodegenerative disorders' were used as keywords during the search period. The Filters applied are: Abstract, Full text, Meta-Analysis, Randomized Controlled Trial, Reviews, in the last 5 years. The articles were analyzed in our unrelenting quest to make sense of the prospects and research gap in gut microbiota-brain-axis. This chapter is a result of this meticulous work. More convincing data from researches on gut microbiota-brain-axis are required to provide clinical significance including neuroimaging studies. Addressing the structural (pathological footprints) and the functional changes (diseases manifestation) involving gut microbiota-brain-axis require a holistic approach. While the pharmacological therapies such as chemotherapeutic and chemobiotic treatment approaches come with low success rates, non-pharmacological interventions are found to be more useful in reversing NDDs. The inability to detect NDDs at an early stage in their clinical history, makes preventive medicinal approaches the must needed and best intervention strategy. Gut-driven treatments have a lot to offer in the management of refractory neurologic diseases.

What We Know About the Actual Role of Traditional Probiotics in Health and Disease

The complex relationship between probiotics and human health goes beyond their traditional function in gut health, generating considerable interest for their broad potential in disease treatment. This review explores the various functions of probiotics, highlighting their impact on the immune system, their benefits for gut and oral health, their effects on metabolic and neurological disorders, and their emerging potential in cancer therapy. We give significant importance to studying the effects of probiotics on the gut-brain axis, revealing new and non-invasive therapeutic approaches for complex neurological disorders. In addition, we expand the discussion to encompass the impact of probiotics on the gut-liver and gut-lung axes, recognizing their systemic effects and potential in treating respiratory and hepatic conditions. The use of probiotic "cocktails" to improve cancer immunotherapy outcomes indicates a revolutionary approach to oncological treatments. The review explores the specific benefits associated with various strains and the genetic mechanisms that underlie them. This study sets the stage for precision medicine, where probiotic treatments can be tailored to meet the unique needs of each patient. Recent developments in delivery technologies, including microencapsulation and nanotechnology, hold great potential for enhancing the effectiveness and accuracy of probiotic applications in therapeutic settings. This study provides a strong basis for future scientific research and clinical use, promoting the incorporation of probiotics into treatment plans for a wide range of diseases. This expands our understanding of the potential benefits of probiotics in modern medicine.

The Influence of Cecal Microbiota Transplantation on Chicken Injurious Behavior: Perspective in Human Neuropsychiatric Research

Numerous studies have evidenced that neuropsychiatric disorders (mental illness and emotional disturbances) with aggression (or violence) pose a significant challenge to public health and contribute to a substantial economic burden worldwide. Especially, social disorganization (or social inequality) associated with childhood adversity has long-lasting effects on mental health, increasing the risk of developing neuropsychiatric disorders. Intestinal bacteria, functionally as an endocrine organ and a second brain, release various immunomodulators and bioactive compounds directly or indirectly regulating a host's physiological and behavioral homeostasis. Under various social challenges, stress-induced dysbiosis increases gut permeability causes serial reactions: releasing neurotoxic compounds, leading to neuroinflammation and neuronal injury, and eventually neuropsychiatric disorders associated with aggressive, violent, or impulsive behavior in humans and various animals via a complex bidirectional communication of the microbiota-gut-brain (MGB) axis. The dysregulation of the MGB axis has also been recognized as one of the reasons for the prevalence of social stress-induced injurious behaviors (feather pecking, aggression, and cannibalistic pecking) in chickens. However, existing knowledge of preventing and treating these disorders in both humans and chickens is not well understood. In previous studies, we developed a non-mammal model in an abnormal behavioral investigation by rationalizing the effects of gut microbiota on injurious behaviors in chickens. Based on our earlier success, the perspective article outlines the possibility of reducing stress-induced injurious behaviors in chickens through modifying gut microbiota via cecal microbiota transplantation, with the potential for providing a biotherapeutic rationale for preventing injurious behaviors among individuals with mental disorders via restoring gut microbiota diversity and function.

Immune Remodeling during Aging and the Clinical Significance of Immunonutrition in Healthy Aging

Aging is associated with changes in the immune system and the gut microbiota. Immunosenescence may lead to a low-grade, sterile chronic inflammation in a multifactorial and dynamic way, which plays a critical role in most age-related diseases. Age-related changes in the gut microbiota also shape the immune and inflammatory responses. Nutrition is a determinant of immune function and of the gut microbiota. Immunonutrion has been regarded as a new strategy for disease prevention and management, including many age-related diseases. However, the understanding of the cause-effect relationship is required to be more certain about the role of immunonutrition in supporting the immune homeostasis and its clinical relevance in elderly individuals. Herein, we review the remarkable quantitative and qualitative changes during aging that contribute to immunosenescence, inflammaging and microbial dysbiosis, and the effects on late-life health conditions. Furthermore, we discuss the clinical significance of immunonutrition in the treatment of age-related diseases by systematically reviewing its modulation of the immune system and the gut microbiota to clarify the effect of immunonutrition-based interventions on the healthy aging.

Cognitive and Emotional Effect of a Multi-species Probiotic Containing Lactobacillus rhamnosus and Bifidobacterium lactis in Healthy Older Adults: A Double-Blind Randomized Placebo-Controlled Crossover Trial

As the population ages, cognitive decline becomes more common. Strategies targeting the gut-brain axis using probiotics are emerging to achieve improvements in neuropsychiatric and neurological disorders. However, the beneficial role of probiotics on brain function in healthy older adults remains unclear. Our aim was to evaluate a multi-species probiotic formulation as a therapeutic approach to reduce emotional and cognitive decline associated with aging in healthy adults. A randomized double-blind placebo-controlled crossover trial was conducted. The study involved a 10-week intervention where participants consumed the assigned probiotic product daily, followed by a 4-week washout period before the second condition started. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) and the Psychological Experiments Construction Language Test Battery. At the emotional level, the Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI) were used. Thirty-three participants, recruited between July 2020 and April 2022, ingested a multispecies probiotic (Lactobacillus rhamnosus and Bifidobacterium lactis). After the intervention, noticeable enhancements were observed in cognitive function (mean difference 1.90, 95% CI 1.09 to 2.70, p < 0.005), memory (mean difference 4.60, 95% CI 2.91 to 6.29, p < 0.005) by MMSE and digit task, and depressive symptoms (mean difference 4.09, 95% CI 1.70 to 6.48, p < 0.005) by BDI. Furthermore, there were significant improvements observed in planning and problem-solving skills, selective attention, cognitive flexibility, impulsivity, and inhibitory ability. Probiotics administration improved cognitive and emotional function in older adults. Limited research supports this, requiring more scientific evidence for probiotics as an effective therapy for cognitive decline. This study has been prospectively registered at ClinicalTrials.gov (NCT04828421; 2020/July/17).

Enterotype-Dependent Probiotic-Mediated Changes in the Male Rat Intestinal Microbiome In Vivo and In Vitro

Beneficial properties of lactic acid bacteria have been known long ago, but particular interest in probiotics has arisen in the last two decades due to the understanding of the important role of intestinal microflora in human life. Thus, the ability of probiotics to support healthy homeostasis of gut microbiomes has received particular attention. Here, we evaluated the effect of a probiotic consisting of Bifidobacterium longum and Lacticaseibacillus paracasei on the gut microbiome of male rats, assessed their persistence in the fecal biota, and compared probiotic-mediated changes in vitro and in vivo. As expected, microbiomes of two enterotypes were identified in the feces of 21 animals, and it turned out that even a single dose of the probiotic altered the microbial composition. Upon repeated administration, the E1 biota temporarily acquired properties of the E2 type. Being highly sensitive to the intervention of probiotic bacteria at the phylum and genus levels, the fecal microbiomes retained the identity of their enterotypes when transferred to a medium optimized for gut bacteria. For the E2 biota, even similarities between probiotic-mediated reactions in vitro and in vivo were detected. Therefore, fecal-derived microbial communities are proposed as model consortia to optimize the response of resident bacteria to various agents.

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.

Alzheimer's Disease and (Phyto) Estrogen Treatment: Modification of Effects by Age, Type of Treatment, and Duration of Use

Background

There is a continued debate on whether menopausal hormone therapy (MHT) protects women against Alzheimer's disease (AD). It is also unclear whether phytoestrogen could be an alternative treatment for AD.

Objective

To investigate whether mixed study findings may be due to differences in age at initiation of MHT and duration of prescription of different types of MHT using meta-analyses.

Methods

After a systematic literature search, meta-analyses were carried out using Cochrane Revman 5.4.1.software including data from large nationwide studies of registered medically diagnosed AD and prescribed MHT. These analyses were stratified for duration and type of treatment, by age at start of prescription of therapy. Insufficient quality data were available for phytoestrogen treatment and AD meta-analyses.

Results

A total of 912,157 women were included from five registries, of whom 278,495 had developed AD during follow-up. Meta-analyses suggested a small increased AD risk after 5-10 years prescription of combination MHT regardless of age, and over 10 years only in women younger than 60 years of age. No association was seen for estrogen alone for women younger than 60 years of age, but AD risk did increase for women over 60 years of age for up to 5 years of MHT prescriptions.

Conclusions

Combination MHT should probably be prescribed for less than 5 years after menopause to reduce risk for AD, while estrogen alone should not be prescribed to women over 60. For phytoestrogen, small treatment trials suggested some benefit of tempeh (fermented soy), which should be investigated further.

Dementia, osteoporosis and fragility fractures: Intricate epidemiological relationships, plausible biological connections, and twisted clinical practices

Dementia, osteoporosis, and fragility fractures are chronic diseases, often co-existing in older adults. These conditions pose severe morbidity, long-term disability, and mortality, with relevant socioeconomic implications. While in the research arena, the discussion remains on whether dementia is the cause or the consequence of fragility fractures, healthcare professionals need a better understanding of the interplay between such conditions from epidemiological and physiological standpoints. With this review, we summarized the available literature surrounding the relationship between cognitive impairment, dementia, and both low bone mineral density (BMD) and fragility fractures. Given the strength of the bi-directional associations and their impact on the quality of life, we shed light on the biological connections between brain and bone systems, presenting the main mediators, including gut microbioma, and pathological pathways leading to the dysregulation of bone and brain metabolism. Ultimately, we synthesized the evidence about the impact of available pharmacological treatments for the prevention of fragility fractures on cognitive functions and individuals' outcomes when dementia coexists. Vice versa, the effects of symptomatic treatments for dementia on the risk of falls and fragility fractures are explored. Combining evidence alongside clinical practice, we discuss challenges and opportunities related to the management of older adults affected by cognitive impairment or dementia and at high risk for fragility fracture prevention, which leads to not only an improvement in patient health-related outcomes and survival but also a reduction in healthcare cost and socio-economic burden.

The Multi-Strain Probiotic OMNi-BiOTiC® Active Reduces the Duration of Acute Upper Respiratory Disease in Older People: A Double-Blind, Randomised, Controlled Clinical Trial

Immunosenescence is the adverse change in the human immune function during aging, leaving older people more prone to an increased risk of infections and morbidity. Acute upper respiratory tract infections (URTIs) are very common among older people, often resulting in continued morbidity and mortality. Therefore, approaches, such as consuming probiotics, that shorten the duration or even reduce the incidence of URTIs in older people are being studied. The aim of this study was to determine the effects of a multi-strain probiotic OMNi-BiOTiC^® Active, which contains 11 live probiotic strains, on the incidence, duration, and severity of URTIs in older people. In this randomized double-blinded placebo-controlled study, 95 participants, with an average age of 70.9 years in the probiotic group and 69.6 years in the placebo group, were randomly allocated to two groups: 10¹⁰ cfu per day of the multi-strain probiotic intervention OMNi-BiOTiC^® Active (49) or placebo (46). The incidence of URTIs in older people after 12 weeks supplementation with OMNi-BiOTiC^® showed no statistically significant difference between the two groups (p = 0.5244). However, the duration of the URTI infections was statistically significantly different between the groups (p = 0.011). The participants that consumed the probiotic had an average duration of illness of 3.1 ± 1.6 days, whilst participants that received the placebo had symptoms for an average of 6.0 ± 3.8 days (p = 0.011). Statistically significant differences in lymphocyte counts in both groups after supplementation (p = 0.035 for the probiotic group and p = 0.029 for the placebo group) and between both groups were found (p = 0.009). Statistically significant differences in eosinophil (p = 0.002) and basophil counts (p = 0.001) in the probiotic groups before and after supplementation with probiotics were also found. Supplementation with the multi-strain probiotic OMNi-BiOTiC^® Active may benefit older people with URTIs. Larger randomised controlled clinical trials are warranted. Clinical Trial Registration; identifier NCT05879393.

Gut-brain axis through the lens of gut microbiota and their relationships with Alzheimer's disease pathology: Review and recommendations

Alzheimer's disease (AD) is a neurodegenerative disorder that affects millions of people worldwide. Growing evidence suggests that the gut microbiome (GM) plays a pivotal role in the pathogenesis of AD through the microbiota-gut-brain axis (MGB). Alterations in GM composition and diversity have been observed in both animal models and in human patients with AD. GM dysbiosis has been implicated in increased intestinal permeability, blood-brain barrier (BBB) impairment, neuroinflammation and the development of hallmarks of AD. Further elucidation of the role of GM in AD could pave way for the development of holistic predictive methods for determining AD risk and progression of disease. Furthermore, accumulating evidence suggests that GM modulation could alleviate adverse symptoms of AD or serve as a preventive measure. In addition, increasing evidence shows that Type 2 Diabetes Mellitus (T2DM) is often comorbid with AD, with common GM alterations and inflammatory response, which could chart the development of GM-related treatment interventions for both diseases. We conclude by exploring the therapeutic potential of GM in alleviating symptoms of AD and in reducing risk. Furthermore, we also propose future directions in AD research, namely fecal microbiota transplantation (FMT) and precision medicine.