The composition of the microbiota varies according to prenatal events, delivery methods, infant feeding, infant care environment, and antibiotic use. Postnatal gut function and immune development are largely influenced by the intestinal microbiota. Emerging evidence has shown that early microbiota colonization may influence the occurrence of later diseases (microbial programming). The vast majority of microbial species (commensals) give rise to symbiotic host–bacterial interactions that are fundamental for human health. However, changes in the composition of the gut microbiota (dysbiosis) may be associated with several clinical conditions, including obesity and metabolic diseases, autoimmune diseases and allergy, acute and chronic intestinal inflammation, irritable bowel syndrome (IBS), allergic gastroenteritis (e.g., eosinophilic gastroenteritis and allergic IBS), and necrotizing enterocolitis. Based on recent advances, modulation of gut microbiota with probiotics, prebiotics, or fermented dairy products has been suggested as a treatment of, or prevention for, different disorders such as IBS, infectious diarrhea, allergic disease, and necrotizing enterocolitis.

To point new insights in the cholestasis that is a complication of both intestinal failure and parenteral nutrition. View on liver disease has recently evolved with the onset of fish oil-based intravenous lipid emulsions (ILE). Focused on the role of ILE in causing liver disease. Reversal of cholestasis was recently achieved in infants with short bowel syndrome, by replacing the 'reference' soybean oil-based ILE by fish oil-based ILE. It is likely that this reversal involves several factors such as the change in n-6: n-3 ratio, the reduction in phytosterol load, the increased provision of alpha-tocopherol as antioxidant agent. Alternative issue might be based on the use of a new generation of ILE aiming to provide n-3 and to reduce n-6 fatty acids load while enhancing alpha-tocopherol intake. New data are based on the use of an ILE containing a balanced proportion of four types of oil as a physical mixture of 30% soybean oil, 30% medium-chain triglycerides, 25% olive oil and 15% fish oil with amounts of alpha-tocopherol calculated according to the number of double bonds. This new emulsion was reported to be beneficial in reversing or preventing liver disease.