Adherence to the Mediterranean diet can beneficially affect the gut microbiota composition: a systematic review

Abstract
Aim Dietary patterns could have a notable role in shaping gut microbiota composition. Evidence confirms the posi‑
tive impact of the Mediterranean diet (MD), as one of the most studied healthy dietary patterns, on the gut micro‑
biota profile. We conducted this systematic review to investigate the results of observational studies and clinical
trials regarding the possible changes in the gut microbiota composition, metabolites, and clinical outcomes follow‑
ing adherence to MD in healthy cases or patients suffering from metabolic disorders.
Methods A systematic literature search was conducted on PubMed, Web of Science, and Scopus databases
until October 2023. Two researchers separately screened the titles, abstracts, and then full‑text of the articles
and selected the relevant studies. Quality assessment of observational and interventional studies was performed
by Newcastle‑Ottawa and Cochrane checklists, respectively.
Results A total of 1637 articles were obtained during the initial search. Ultimately, 37 articles, including 17 observa‑
tional and 20 interventional studies, were included in this systematic review. Ten observational and 14 interventional
studies reported a correlation between MD adherence and microbiota diversity. Faecalibacterium and Prevotella were
the most frequent bacterial genera with increased abundance in both observational and interventional studies;
an Increment of Bacteroides genus was also reported in observational studies. Better glycemic control, lowering fat
mass, better bowel movement, decreased bloating, inflammation, and hospitalization risk were the reported clinical
outcomes.
Conclusion Adherence to the MD is associated with significant beneficial changes in the gut microbiota diversity,
composition, and functions and major clinical improvements in most populations.
Keywords Mediterranean diet, Dietary intervention, Gut microbiota