This new study challenges the previous belief that gut bacteria are stable from @ 12 months old by showing these bacteria continue changing until about 3 years of age. This means there is a 'window' in these early years where the gut bacteria are more vulnerable to external factors. It seems that the longer a child is breastfed, the longer the bacteria is encouraged to flourish.
APC scientists have shown that brain levels of serotonin, the ‘happy hormone’ are regulated by the amount of bacteria in the gut during early life. Their research is being published today in the leading international psychiatry journal, Molecular Psychiatry.