The Effect of Diet and Probiotics on the Human Gut Microbiome

Abstract

The term microbiome defines the overall amount of microbial genes harbored by the microbiota, the microbes inhabiting the human intestinal tract, this makes up approximately 150 thousands genes that add to our genome to assembly an interactive meta-genome. Probiotics, defined according to the FAO/WHO documents and by an ISAPP consensus meeting have always been part of human diet in a variety of fermented foods, and, nowadays are the object of possible interventions aimed at restoring microbiota healthy balance. Recent genomic studies are clearly suggesting that the microbiota plays a role in a large number of physiological functions, far beyond the digestive ones. The most relevant symbiotic functions of microbial community structure and its genomic composition are represented by its critical contribute to resistance to the infections, and more broadly by its influence on the immune system activity which in turn modulates the composition of the gut microbiota. Recent advances in neurosciences have also shown the relevant role of the so-called “Gut-brain axis” meaning that gut’s bacterial community has a deep impact on the nervous system. These relevant roles of microbiota make it worthwhile to study factors that shape its composition. This is indeed influenced by several internal and external factors such as the initial intestinal colonization at birth, the genetic background of the host, intercurrent antibiotic treatments and, on top of all these, diet. The possible changes of microbiota during pregnancy are still under debate. Gut microbiota is probably undergoing a dramatic remodeling in order to exploit food energy at its best. Changes that might impact and contribute to changing immunomodulation by the end of pregnancy are still controversial. Pregnant stool samples collected during the third trimester showed an enrichment in Proteobacteria and Actinobacteria, similar to the situation detected in inflammatory bowel disease and obesity, as well as the reduction of health-related bacteria such as Faecalibacterium, a butyrate-producing bacteria with anti-inflammatory effects. These intriguing findings are in contrast with those reported later by other studies in which little or no modifications of the faecal microbiota composition were reported during early and late pregnancy. These controversies do not dwarf the importance of macrobiotic in pregnancy, rather they underline the quest for future studies