The Mediterranean Diets’ Effect on Gut Microbial Composition in Comparison with the Western Diet: A Literature Review

Background: In recent years, the scientific interest about the possible role of dietary attitudes on gut microbiota modulation has been increasing. Objective: The present literature review aimed to analyze the effect of Mediterranean diet adoption on gut microbial composition, in comparison with the Western diet. Methods: From an initial number of 38, 21 recent studies were selected using comprehensive scientific databases and relative keywords, such as microbial composition, dietary attitudes, and beneficial effects. The selected studies were recently published based on animal models, human interventional trials, metanalyses and gut microbiome analysis, such as metagenomics. Results: According to the basic findings of the present review study, Mediterranean diet adherence leads to a gut microbial richness and richer diversity as well as a higher abundance of genera Lactobacillus, Faecalibacterium, Oscillospira, Bifidobacterium, Eubacterium species, that stimulate the production of total short-chain fatty acids. This diet also leads to a lower Firmicutes / Bacteroidetes ratio due to the increase of Bacteroidetes and decrease of Firmicutes, accompanied by a decrease of circulating Trimethylamine N oxide levels and a reduction in abundance of Ruminococcus, Lachnospiraceae, Proteobacteria and Coprococcus, in comparison to the Western diet. Conclusion: Further understanding of the multifactorial effect of both Mediterranean and Western diet on gut microbiota could allow the establishment of nutritional educational programs and nutritional policies with aim to improve human health by modulating gut microbial composition.