During natural birth, breastfeeding and general nursing of the infant, bacteria are transferred from the mother to the infant. This helps establishing the early microbiome in the infant. If this transfer of bacteria is disrupted e.g. by caesarean birth, or early cessation of breastfeeding, the colonization pattern may change. Studies have shown that the microbiome may influence the infant&rsquo;s immune, metabolic and neurological programming. A disturbed colonization may have effects on the general health of the infant from birth through adulthood.<br />

Diet plays a significant role in shaping the microbiome and dietary changes can induce large bacterial shifts in short time. The relative content and source of proteins, carbohydrates and fat in the diet all influences the composition and functioning of the microbiota. The microbiome may affect host immune and metabolic parameters, with potential implications for human health.<br />

Antibiotic use may cause severe disturbances to the gut microbiome. The immediate effect is a reduction in bacterial richness and total biomass including beneficial bacteria such as <em>lactobacilli </em>and <em>bifidobacteria</em>. The return to baseline levels may be slow and repeated antibiotic courses aggravate this. When the normal microbiome is disturbed, antibiotic-resistant and pathogenic species may proliferate causing inflammation, barrier disruption and intestinal damage.

Stress has been shown to influence the gut microbiome via the gut-brain axis. Among other modifications, acute and long-term stress reduces the abundance of health beneficial <em>Lactobacillus </em>and <em>Bifidobacterium</em>. Such microbiome shifts may result in inflammation, increased gut permeability, immunomodulation, and intestinal damage.<br />