Let's say he's going through a period of rapid brain growth, when he needs more of the fats in the milk to build brain cells. (breastfeedingtoday-llli.org)
This is thought to be related to a human baby's rapid brain growth in infancy, compared to other mammals. (breastfeeding.asn.au)
While 63 % of parents identified this correctly, more than 34 % said that the time of most rapid brain growth is 3 to 5 years, a significant underestimation of the importance of the earliest years. (zerotothree.org)