Many mothers of infants diagnosed with phenylketonuria (PKU) are told that they will be unable to breastfeed.  Even mothers who were committed to the idea of breastfeeding have relunctantly given up their plans to breastfeed their babies after the diagnosis.  However, the good news is that it is very possible to partially breastfeed a baby with PKU.

PKU is a disorder that causes difficulty for the body to break down certain types of food.  From birth, people with PKU lack the enzyme responsible for breaking down phenylalanine, one of the 20 major amino acids that form the proteins found in everyday foods. People with PKU must avoid protein because, even though everybody needs small amounts of phenylalanine, excess amounts stay in their bodies indefinitely and interfere with brain function. An improper diet can lead to concentration problems, depression and brain damage.

In the United States, one baby out of every 10,000-15,000 is born with PKU.  There are currently around 15,000 people in the United States with disorder.

Despite the special needs of babies with PKU, they can still be largely breastfed.  Since human milk is lower in phenylalanine than cow's milk formula, a mother can continue breastfeeding while supplementing her baby's diet with the low-phenylalanine formula.  Some women mix the PKU formula with their expressed milk and bottle feed, while most women alternate between the required formula and breastfeeding.  You can read the personal stories of over twenty mothers who breastfed their babies with PKU and the ways they handled it here.

The Minnesota PKU Foundation says:

With support from the clinic and your dietitian you can have a successful part time breastfeeding experience. How much or often you will be able to breastfeed will depend upon the severity of the PKU the child has. Different clinics and staff support different methods. Some clinics will suggest rotating feedings between the special formula and breastfeeding/breast milk. Other clinics will have mothers supply both breast milk and formula at each feeding. You should discuss these options with your clinic staff.

You can read another mother's story of how she successfully breastfed her baby with PKU for 18 months at the La Leche League website.

The University of Minnesota offers the website "A Place for Us" for children and teens with PKU, as well as their families.