A narrative review of the functional components of human breast milk and their potential to modulate the gut microbiome, the consideration of maternal and child characteristics, and confounders of breastfeeding, and their impact on risk of obesity later in life.

Nutritional exposure and, therefore, the metabolic environment during early human development can affect health later in life. This can go beyond the nutrients consumed; there is evidence that the development and modulation of the gut microbiome during early life can affect human growth, development, and health, and the gut microbiome is associated with the risk of obesity later in life. The primary aim of this review was to evaluate existing evidence, to identify the components of human breast milk, which may modulate the gut microbiome, and to assess the impact of the gut microbiome on the risk of becoming obese later in life. This review also considers maternal and child characteristics, and confounders of breastfeeding and how they impact on the infant gut microbiome. Current evidence supports a positive association between fecal, branched short-chain fatty acids and human milk oligosaccharide diversity and a gut microbiome associated with better metabolic health. A negative correlation was found between microbiome diversity and human milk oligosaccharide evenness, which was associated with a greater fat mass and percentage of fat. The components of human breast milk, including oligosaccharides, probiotics, milk fat globule membrane, and adiponectin, were hypothesized to positively influence infant growth and body weight by modulating the microbial diversity and composition of the gut. Maternal diet, timing and duration of breast feeding, and the mode of delivery were all shown to affect the human milk microbiota. However, more experimental studies with long follow-up are required to shed light on the governing mechanisms linking breast milk components with a diverse infant microbiome and healthier body weight later in life.