Jay,
Persons with PKU (phenylketonuria) are unable to change phenylalanine
into tyrosine.  Phenylalanine in high levels poisons the developing
brain, leading to severe mental retardation and muscle contractures.
People with PKU need a diet very low in phenylalanine for about 6 years.
 Mothers with PKU need to resume the low phenylalanine diet during
pregnancy and breastfeeding to avoid poisoning their infants brain
through their blood (placenta) or milk.  All protein foods contain
phenylalanine, so the only choice for moms with PKU is a diet of fruits
and a few veggies, and a special protein formula (which taste pretty
nasty).  It is commendable that this mother is willing to restrict her
diet to be able to breastfeed her infant, and in my opinion, there should
be some assistance provided her to buy the formula she needs.
--
Catherine Watson Genna, IBCLC  NYC  [log in to unmask]