The first 1,000 days is a critical window when the gut and immune system develop rapidly, as babies move from a protected environment to one where they are exposed to lots of immune challenges. The development of healthy gut microbiota is essential for immune system development and function. Early nutrition is the main influence on initial microbiota composition; and optimal nutrition fine-tunes the immune system and sets up metabolic homeostasis in early life, influencing long-term health.

Breastmilk is the best possible source of nutrition for a healthy microbiota composition. Recent research suggests around 30% of gut microbiota in breast-fed infants comes directly from their mother’s milk.

As well as being an optimal source of beneficial bacteria, breastmilk contains prebiotic human milk oligosaccharides which positively shape the infants gut microbiota. These prebiotics pass intact to the lower part of the infants’ gut where they are selectively fermented by beneficial bacteria such as bifidobacteria — allowing the amplification of these bacterial populations. This fermentation process also creates postbiotics — bioactive components that play an important role in the regulation of biologic activity in the gut.