[A new component of breast milk: microRNA].

MicroRNA (miRNA) is a class of non-coding endogenous small molecule single strand RNA which is found in human body fluids. In recent years, miRNAs have been found in breast milk and parts of miRNAs are related to immune organ development and regulation of the immune function in infants. This article summarizes the functions of miRNA in breast milk and evidence-based clinical practice, and the differences between microRNA content and species in breast milk and cow milk. Understanding the role of miRNA can bring new opportunities for childhood nutrition research.