A Day in the Life with PKU: Phe Calculation: Following the Diet Prescription

For those of you who know little to nothing about PKU, let me explain a little bit here.  Phenylketonuria is a rare genetic (inherited) metabolic trait in which a gene mutation or deformity causes a specific liver enzyme not to be able to process phenylalanine ("phe" for short), which is one of the amino acids found in protein.  In other words, Carson's body cannot process part of protein, so it stays in his blood stream, which is dangerous for his brain if it is too much.  This is tested for in all newborn babies in most states through the Newborn Screening Program, which is why they stick babies' heels in the hospital after they are born.  It is just one of several disorders they test for.  The importance of finding it so early is that treatment is best started right away to avoid brain damage caused by high levels of phe in the brain.  The treatment is a low protein diet, preferably for life.  Phe levels are tested in the blood regularly to maintain levels within an acceptable range.

Once phe levels and phe tolerance are established, a nutritionist and physician specialist work together to determine a patient's phe prescription, or the amount of phe the body can handle and stay within the normal range.  As babies and through the toddler years, children grow so rapidly that this diet is monitored and changed frequently.  Once growth slows down, it is easier to keep a steady prescription.  Carson is currently allowed 350mg phe per day, and has been on this Rx for over a year, I think.

So how do we figure out how much phe he gets in his diet?  Protein is a listed ingredient on food nutrition labels, but phe is not!  Phe is just one part of protein!  Well, we have this wonderfully fabulous book I often refer to as the "Food Bible", or Carson's Phe Book, called the Low Protein Food List.  It was put together by a remarkable woman  named Virginia Schuett, who has done SO MUCH for the PKU community over the years.  She worked as a nutritionist at a PKU clinic in Wisconsin and founded the National PKU News Organization (www.pkunews.org).  Thanks to the tremendously hard work of her and her team, we have this awesome resource for keeping track of Carson's diet!

Inside, this awesome book contains the phenylalanine content of almost any food you can imagine.  I scour through it from time to time searching for new foods that Carson can try.  By now I have so many things memorized that Carson has been eating for a few years, I don't even open the book as much anymore.  I had to look up lettuce a few weeks ago when he started eating salad.  I plan on taking the book with me next time I go grocery shopping so I can check out some of the new gluten-free products to see if there are any he can try.  Below is a sample of a page from the book showing how the nutritional and phe content is listed for food items, plus a sample from Carson's notebook.  Each day (when I don't slack) I write a page in his "Food Diary" detailing what he ate, how much of it, and the phe content.  Then I add it up for the day and try, as we go, to make sure it is as close to 350mg as we can get.  Some food items have a specific measurement listed, like 1/2 cup, some I have to measure by the gram and weigh them on our digital kitchen gram scale.  Who ever said you would never use math in real life?  Trust me kids, math is my life now!

First it lists the brand, if there is one; then the name of the food, next the measurement of a given portion size (like 1/2 cup), then the weight in grams of that portion, and the last thing I look at in the first gray column is the mg phe per that portion size.

See how I keep a running tab of mg of phe
to the side?  This helps me know what
Carson can eat next the rest of the day. 
For example, 1/2 cup of rice is 90mg phe, so he would not have been able to fit that in without going way over 350mg.

I do most of it in my head now, or refer back to previous pages and copy the figures.  I also have learned how to "eyeball" a lot of measurements, like today, when we ate at O'Charley's, Carson ate broccoli, and it was a much larger portion than we usually get.  I estimate, after weighing several portions at different restaurants, we usually get 50 to 60 grams of broccoli; today looked more like 80g!  Then I would calculate, for example, (I still use the amount from the previous book version), since there is 0.83mg phe per gram of broccoli, that 80g x 0.83mg=66mg phe.  It is amazing how quickly you learn to adapt to things like this.  It has just become like second nature to me, and for that I am so thankful.  I am trying to start teaching Carson to count certain things that he eats, like potato chips, for example.  I have figured, since in the book it says 95mg for  1oz of most brands of chips, and say Pringles are about 14 chips per 1oz serving, that 1 Pringle chip has 6mg phe.  So I just count the number of chips he eats instead of weighing them on a scale (this is why I like chips that are more uniform in size and shape! lol).

 I hope I am able to teach Carson all of the tricks I am learning in managing his diet, so maybe one day he will be independent enough to do it himself.