There is no cure for PKU, but treatment can prevent intellectual disabilities and other health problems.1 A person with PKU should receive treatment at a medical center that specializes in the disorder. (Visit the Resources and Publications section for ways to locate a center.)
The PKU Diet
People with PKU need to follow a diet that limits foods with
phenylalanine. The diet should be followed carefully and be started as
soon after birth as possible. In the past, experts believed that it was
safe for people to stop following the diet as they got older. However,
they now recommend that people with PKU stay on the diet throughout
their lives for better physical and mental health.
It is especially important for a pregnant woman with PKU to strictly follow the low-phenylalanine diet throughout her pregnancy to ensure the healthy development of her infant.
People with PKU need to avoid various high-protein foods, including:
- Milk and cheese
- Eggs
- Nuts
- Soybeans
- Beans
- Chicken, beef, or pork
- Fish
- Peas
- Beer
People with PKU also need to avoid the sweetener aspartame,
which is in some foods, drinks, medications, and vitamins. Aspartame
releases phenylalanine when it is digested, so it raises the level of
phenylalanine in a person's blood.
Often, people with PKU also have to limit their intake of
lower-protein foods, such as certain fruits and vegetables. However, a
PKU diet can include low-protein noodles and other special products.
The amount of phenylalanine that is safe to consume differs for each
person. Therefore, a person with PKU needs to work with a health care
professional to develop an individualized diet. The goal is to eat only
the amount of phenylalanine necessary for healthy growth and body
processes but not any extra. Frequent blood tests and doctor visits are
necessary to help determine how well the diet is working. Some
relaxation of the diet may be possible as a child gets older, but the
recommendation today is lifelong adherence to the diet. Following the diet is especially important during pregnancy.
However, the PKU diet can be very challenging. Getting support from
friends and family or a support group can help. Sticking with the diet
ensures better functioning and improved overall health.
A PKU Formula
People who follow the PKU diet will not get enough essential nutrients from food. Therefore, they must drink a special formula.
A newborn who is diagnosed with PKU should receive special infant
formula. The formula may be mixed with a small amount of breast milk or
regular infant formula to make sure the child gets enough phenylalanine
for normal development but not enough to cause harm.
Older children and adults receive a different formula to meet their
nutritional needs. This formula should be consumed every day throughout a
person's life.
In addition to the formula, health care professionals may recommend
other supplements. For example, fish oil may be recommended to help with
fine motor coordination and other aspects of development.1
Medication for PKU
The U.S. Food and Drug Administration (FDA) has approved the drug
sapropterin dihydrochloride (Kuvan®) for the treatment of PKU. Kuvan® is
a form of BH4, which is a substance in the body that helps break down
phenylalanine. However, having too little BH4 is only one reason a
person may not break down phenylalanine. Therefore, Kuvan® only helps
some people reduce the phenylalanine in their blood. Even if the
medication helps, it will not decrease the phenylalanine to the desired
amount and must be used together with the PKU diet.
When the FDA approved Kuvan®, the agency suggested that research on
the medication continue to determine its long-term safety and
effectiveness.
Other Treatments for PKU
NICHD-supported researchers and other scientists are exploring
additional treatments for PKU. These treatments include large neutral
amino acid supplementation, which may help prevent phenylalanine from
entering the brain, and enzyme replacement therapy, which uses a
substance similar to the enzyme that usually breaks down phenylalanine.
Researchers are also investigating the possibility of using gene
therapy, which involves injecting new genes to break down phenylalanine.
That would result in the breakdown of phenylalanine and decreased blood
phenylalanine levels.
