Diet is a reservoir of microbes and the feeding for human resident microorganisms, therefore, it is inevitably linked to diversity and functionality of the oral and intestinal microbiota. The oral and, especially, the intestinal microbiota are valuable “traits d'union”/determinants between diet and human well being. As succinctly stated in the document Horizon 2020 (page 56), “a better understanding of the determinants of health is required in order to provide evidence for effective health promotion and disease prevention. Approaches will include the long-term study of cohorts and their linkage with data derived from "-omics" research, and other methods”. Excluding obvious geographical differences, three main dietary habits are worldwide diffused: omnivore, vegetarian and vegan. A cross-search for "human gut microbiota" and "health" in the ISI Web of Knowledge database, results in more than 550 hits, only in the last 5 years. Less than 10 hits come out combining the terms “vegetarians” and "human gut microbiota".
Based on the above considerations, the overall objective of this project is to estimate the intake of microorganisms based on the omnivore, vegetarian and vegan diets, and to find the relationship between diet and saliva and fecal microbiota, through high-throughput and integrated meta-omics (genomic, transcriptomic, proteomic and metabolomic) analyses. Several questions are still debated within this context. For instance, what is the daily intake of microbes and their role on the balance of the intestinal microbiota? How is the intestinal microbiota affected by the main types of diet (omnivore, vegetarian and vegan)? Which are the prevailing microbial groups at intestinal level, depending on the type of diet? What is the presumptive contribution of each microbial group in maintaining the host health? The quantitative and qualitative determination of the main microbial groups harboured in foods, depending on dietary habits, responds to an earlier question and coincides with one of the objectives of this project. The estimation of the diversity (genomics), functional activity (transcriptomics and proteomics) and metabolites (metabolomics) of, especially, the fecal microbiota coincide with the holistic approach of this project and responds to several of the earlier questions. Considering the close correlation between the balance of different microbial populations in various niches of the human body and the onset of metabolic pathologies, this project shall furnish novel knowledge that may highlight possible relationships between diet and dismetabolisms. The results of this project will have the objective to manage the diet in a way
that permits the modulation of microbial populations and favours those responsible for the synthesis of beneficial compounds and for pathogen inhibition. Diet has to be considered as the most appropriate and inexpensive tool to determine a stable and favourable oral and intestinal microbiota, which prevents diseases and guarantees human longevity. These overall objectives of the project shall be reached on the basis of specific targets, such as: (i) the identification of biological, molecular and metabolic markers specific to the type of diet; (ii) the estimation of the differences in the microbiota and metabolome of saliva and feces, both among individuals and between types of diet; (iii) the estimation of the qualitative and quantitative differences on the microbial intake connected to the type of diet; and (iv) the identification of the functional features of fecal samples related to the type of diet, which can be regarded as indicators of disease susceptibility.
Given the large number of Research Units involved in this project as well as the numerous International partners willing to collaborate, an equally important objective is to establish a permanent National and International platform for this and future projects.