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

Abstract

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.

Hirami lemon (Citrus reticulata var. depressa) modulates the gut–brain axis in a chronic mild stress-induced depression mouse model

“…36 Studies have shown that positive regulation of the gut microbiota by probiotics, prebiotics, antibiotics, dietary supplements, and faecal microbiota transplantation can be effective treatments for MDD and neuropsychiatric disorders. 63…”

“…36 Studies have shown that positive regulation of the gut microbiota by probiotics, prebiotics, antibiotics, dietary supplements, and faecal microbiota transplantation can be effective treatments for MDD and neuropsychiatric disorders. 63 In recent decades, there has been increasing attention given to the potential of dietary supplements to modulate the composition and activity of intestinal microbiota. Citrus polyphenols have been identified as having the ability to influence the gut microbiota composition and function, and exert potential neurological benefits.…”

Normative cognition and the effects of a probiotic food intervention in first grade children in Côte d’Ivoire

“…Indeed, such studies are warranted given recent evidence pointing to probiotic effects on attention tasks in Thai children (6-12-year-olds) after prolonged (12 weeks) administration 49 . Moreover, multiple reviews published since this study was conducted have found evidence for a potential role of probiotics and prebiotics in improved cognitive function in humans [50][51][52] . Importantly, we note that all studies finding effects engaged in uninterrupted and/or prolonged (12 or more weeks) probiotic administration, underscoring the importance consistent administration will play in future investigations.…”

Gut-brain axis: Focus on gut metabolites short-chain fatty acids

“…An earlier systematic review summarized the human randomized clinical trials regarding the effects of gut microbiota shaping on cognitive functions, including probiotics, prebiotics, synbiotics, and fecal microbiota transplant (FMT). The results showed that probiotic supplementation and FMT could improve cognitive functions in subjects, irrespective of their health; however, supplementation with prebiotics in unhealthy subjects did not provide any cognitive improvement[ 71 ]. Most studies are descriptive research.…”