Systematic Reviews
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 21, 2021; 27(39): 6715-6732
Published online Oct 21, 2021. doi: 10.3748/wjg.v27.i39.6715
Microbiota shaping — the effects of probiotics, prebiotics, and fecal microbiota transplant on cognitive functions: A systematic review
Simone Baldi, Tiziana Mundula, Giulia Nannini, Amedeo Amedei
Simone Baldi, Tiziana Mundula, Giulia Nannini, Amedeo Amedei, Department of Experimental and Clinical Medicine, University of Florence, Florence 50134, Italy
Amedeo Amedei, SOD of Interdisciplinary Internal Medicine, Azienda Ospedaliera Universitaria Careggi, Florence 50134, Italy
Author contributions: Baldi S and Mundula T contributed equally to writing the manuscript; Baldi S, Mundula T, Nannini G, and Amedei A contributed to the conceptualization and design of the study; Baldi S, Mundula T, Nannini G, and Amedei A critically revised the paper; Amedei A contributed to the supervision of the study; Baldi S, Mundula T, Nannini G, and Amedei A approved the final version of the paper.
Supported by Università degli Studi di Firenze, No. EX60%2020.
Conflict-of-interest statement: The authors declare no competing interests.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Amedeo Amedei, BSc, Reader (Associate Professor), Department of Experimental and Clinical Medicine, University of Florence, Largo Brambilla 3, Florence 50134, Italy. aamedei@unifi.it
Received: February 25, 2021
Peer-review started: February 25, 2021
First decision: April 18, 2021
Revised: May 12, 2021
Accepted: September 2, 2021
Article in press: September 2, 2021
Published online: October 21, 2021
Processing time: 236 Days and 19.6 Hours
ARTICLE HIGHLIGHTS
Research background

Due to the global population aging, cognitive impairments will affect approximately 115 million people by 2050. Since current therapies only attempt to counterbalance cognitive disorders, many recent studies recently highlighted the central role of the gut microbiota in brain health.

Research motivation

The pathogenesis of several cognitive disorders is still not fully understood; however, it has been recently established that a dysregulated gut-brain axis communication is associated with the onset and persistence of neurodegenerative diseases. Thus, gut microbiota manipulation could restore a functional gut-brain axis improving cognitive functions.

Research objectives

Since the evidence derived from human randomized clinical trials (RCTs) is currently limited, the main purpose of this systematic review was to detect the currently available RCTs, to define better the effects of probiotics, prebiotics, and fecal microbiota transplant (FMT) on cognitive functions.

Research methods

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 types of study design and setting, characteristics of the studied population, kind of the 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.

Research results

The analysis of the 23 included in our systematic review highlighted that, although the different type and posology of administration and the various cognitive tests and questionnaires adopted, both probiotics supplementation and FMT improved the cognitive functions in most of healthy people and patients affected by different neurological pathologies.

Research conclusions

The gut microbiota manipulation could represent a good strategy to counteract gut dysbiosis and so ameliorate cognitive dysfunction.

Research perspectives

The supplementation of probiotics and FMT could represent a non-invasive successful strategy to restore gut eubiosis and enhance cognitive functions in healthy people and patients with different neurological/neurodegenerative diseases.