The Response of the Gut Microbiota to Dietary Changes in the First Two Years of Life.

The infant gut microbiota undergoes significant changes in the first two years of life in response to changes in the diet. The discontinuation of the milk-based diet of the first year and the introduction of solid foods in the second year of life results in a decline in , a shift from infant strains of to adult strains which preferentially metabolize oligosaccharides derived from plants rather than from milk, a surge in short chain fatty acids such as acetic, propionic and butyric acid from newly acquired commensal , and the transformation of primary bile acids into secondary bile acids by a limited number of newly acquired and highly specialized spp. By 3 years of age, diet and gut microbiota closely resemble those of adults. Gut bacteria required for the production of SCFAs and secondary BAs are potential targets for the intervention of microbiome-related diseases.