Have you ever thought about how much protein you eat? We hear things on the news, read in magazines, talk to our friends or doctors about our carbohydrate
or fat intake but how many of us think about our protein intake? Unless you are a body builder or athlete, it’s usually not a big concern. In fact
the “normal” diet tends to be much higher than the recommended intake for protein. Take a standard dinner – maybe it’s a piece of chicken, some vegetables
and a starch such as rice. That could provide anywhere from 40 to 45 grams of protein depending on the portion size (and we all know how much we love
our portions!). The recommended intake for an adult is 45-50 grams – A DAY! See, we meet that with NO problem!
But what happens if your body can’t have that much protein?
What if you are born with a metabolic condition that makes protein difficult for your body to process, potentially even fatal? Sounds dramatic doesn’t
But for patients that are born with certain inborn errors of metabolism such as Phenylalanine Hydroxylase Deficiency, Maple Syrup Urine Disease or one
of the Urea Cycle Disorder this is their daily struggle. They have to maintain a good, healthy diet but limit their protein intake to what their body
can handle. They may be allowed as little as 3-4 grams of protein per day. Or as much as 25-30 grams.
How do they do it? How do they eat well, meet their nutritional needs but maintain a protein restriction to keep their disease under control?
If you think about it, a glass of milk (8 ounces) has 8 grams of protein. So what happens when a patient can only have 4 grams of protein per day? Obviously
they aren’t drinking milk. They also aren’t eating cheese or yogurt, they aren’t having a chicken breast at lunch or eating a loaded baked potato at
dinner. They aren’t grabbing a cheeseburger in the drive thru on a trip or having a big ice cream cone to celebrate a good report card. In this world
of high protein, how do they make it through a day?
Let’s look at a patient with Phenylalanine Hydroxylase Deficiency or PAH Deficiency.
You may know this disease by its better known title, PKU or Phenylketonuria. PAH deficiency is the inability of the body to breakdown phenylalanine,
an amino acid. Amino acids are the building blocks of protein so any foods that have protein in them will have phenylalanine. Because the Phenylalanine
Hydroxylase enzyme is not functioning as it should, phenylalanine, or phe as we sometimes call it, builds up in the blood stream and crosses into
During the most important time of brain development, birth to about 8 years of age, phe is toxic in high amounts and can cause severe intellectual
disability if not controlled. Phenylalanine is needed in some amount however for growth and development. The other complication is that the enzyme
breaks phenylalanine down to tyrosine, another amino acid. When unable to process phenylalanine, the body becomes deficient in tyrosine which is
very important in brain and hormone functions. So as you can see, it’s not just simply “limit protein” as there are many other things that need
to be taken into consideration.
So, how do we take care of these patients?
Once the Metabolic Treatment Team at the Greenwood Genetic Center receives a call that a baby has screened positive for PAH deficiency on the state
newborn screen, they get in touch with the family and bring them to clinic as quickly as possible. Since the newborn screen is just that, a screening
tool, further testing is completed to find out if they are a true positive for the disorder.
In the meantime, it’s better to be safe than sorry so they are started on treatment immediately.
Since breastmilk and all infant formulas contain phenylalanine, these must be provided in very limited amounts. The team determines how much phenylalanine
they think the infant can tolerate, just enough for continued growth and brain development. But they want to make sure they aren’t getting too
much which will cause brain damage.
And since the breastmilk or formula intake is limited for phenylalanine, how is the baby going to get the additional nutrients needed to promote growth?
Thankfully we have special metabolic formulas for all of the different disorders that are made to specifically treat these patients. For PAH deficiency,
the metabolic formula provides all vitamins, minerals, carbohydrates and fats that are needed for growth of an infant. But the protein in these
formulas is broken down to its very basic form, amino acids, and the phenylalanine is removed. This way the baby will still get all of the amino
acids needed for their nutritional needs but they won’t get an excessive amount of phe. These formulas also supplement tyrosine since the infant
can’t make that with the lack of the enzyme.
How do we know it’s working?
To monitor how well an infant is tolerating the phenylalanine content of their diet, they have to have levels checked twice a week. This means the
parents or caregivers must stick the heel or finger and fill out a blood spot card which is sent in for evaluation. Based on the result, their
phe intake may be increased or decreased to maintain it within the goal treatment range.
There are many things that can affect the phe level, not just what the child is eating. Growth requirements, immunizations, illnesses, bottle or formula
refusal and teething are just some of the normal occurrences in childhood that can lead to a phe level going too high or too low. Because the phenylalanine
intake is so tightly controlled, the caregiver must weigh formula on a gram scale to ensure accurate measurement. This means that if they go on
a family vacation, the gram scale, extra batteries, formula recipe and extra cans of the metabolic formula are packed along with the normal things
a baby needs.
The metabolic formulas are not found in the regular grocery stores or even pharmacies. For the state of SC, metabolic formula is provided by the health
department which is an extremely helpful program. These formulas are much more expensive than regular infant formulas. Some states do not provide
formula and that makes it very difficult for caregivers to maintain the appropriate treatment plan. For our patients, the caregivers must monitor
their supply so that they can contact the health department early enough to get the formula ordered, delivered and picked up.
Running out of metabolic formula is not an option.
For the infant, the treatment plan is fairly simple – measure breastmilk or regular infant formula to provide the goal amount of phenylalanine, measure
the metabolic formula in the amount needed to supplement their nutritional needs, mix and give to the baby.
But then the fun really begins when they start solid food!
Stay tuned for the next post to see how we manage these children’s dietary needs!