I took a breastfeeding course when I was working as a public health nurse and this was discussed often. They referred to it as painting the gut! It is like you are literally painting a protective film in your babies intestines
this is also a reason that they recommend not starting solids until 6 months and not giving formula. As soon as you start introducing something else you begin to loose that protective layer. Another neat fact About Breastfeeding..... Mothers who have HIV can breastfeed as long as they strictly breastfeed. once they begin solids they need to stop breastfeeding completely. When they only breastfeed the HIV virus is not spread to the baby even though it is carried in the breast milk. This is because of the protective layer. Now here they may still recommend formula instead, but in other third world countries there is no other option and they have learned this is the way to prevent the spread. Pretty cool in my opinion