I am the mother of a now 6 week old PKU daugter and breastfeeding is the best food for our babies still. You have to supplement with the phe-free formula according to the amount of phe they can tolerate. The nutritionist I see has me pump my milk then mix 10 oz. of it with 44 grams of the phenex formula and add water. I then make bottles from this and this is our current recipe but it changes based on her levels. I also do breastfeed directly some time each day. It is very important to follow the doctors directions. Breastmilk is lower in phe than off the shelf formula.