Phe allowance vs. phe range


For as long as I can remember I have always been given one specific number in regards to my phe tolerance. I have always been told to consume X amount of phe—no more and no less. As you can imagine, and if you have PKU I am sure you understand, this leaves little room for flexibility. Sticking to this allowance so rigidly can mean adding high phe items to your formula if you are short some phe. Often times it also means not eating at the end of the day even when you are hungry.

For nearly two years my levels have been coming back ridiculously low; never higher than 1.7 mg/dl. As wonderful as this might sound sometimes low levels can cause just as many issues as high ones. For nearly two years I did exactly as I was told, and my phe levels continued to come back extremely low. Each time I was told that I need to get all of my phe in. No one ever thought ‘gee if her levels are coming back consistently low maybe her tolerance is actually higher than what we have been telling her.’ It never occurred to anyone on my medical team that maybe they were giving me the wrong number to aim for.

Have no fear though, because I eventually figured the problem out, albeit on my own. I just wasn’t okay with accepting that I was apparently doing something wrong and not complying with my diet. Being the stubborn person that I am after my level came back as 0.3 mg/dl and I was once again told I need to follow my diet better I decided enough was enough. To make a long story short I told my dietitian that I was increasing my phe intake, because clearly I needed more. I took things into my own hands and increased my tolerance by 300 mg of phe. Surprise! Surprise! My level came back as 3.6 mg/dl! That was the highest it had been in two years! After that I decided to be adventurous, and I increased my phe again. I did two blood tests at this higher allowance after my second increase, and both levels came back on the lower end of five.

Here’s my question: my level was good when I was consuming both 1200 and 1500 mg of phe, so why do I need to stick to one specific amount? I tend to aim closer to 1200 mg of phe, because I would prefer my levels to be lower. However, on days when I am still hungry late at night why can’t I go up to 1500 mg of phe since I know my level will still come back in a safe range? What’s wrong with eating a little more if you know your level will still come back okay? It just makes me wonder how high can others with PKU go before their levels get too high, and should I be thinking about my tolerance as 1200-1500 mg of phe each day rather than just 1200 mg of phe? This new thinking allows so much more flexibility in my diet. I wonder if we would have more people ‘complying’ with the diet if we thought about it in these terms and were able to find a lower and upper limit for phe and aim for something in the middle knowing that we could go slightly lower or higher if needed. This just seems more realistic then saying ‘eat this amount and only this amount.’ It seems more flexible for the busy lives that I am sure we all lead.

Any thoughts? Has anyone else ever decided to push the limits a little bit and think about their tolerance more as a range rather than one specific amount? Just curious if I am the only one who has found that they can actually tolerate more phe while still having good levels. I guess this is another reason why we need to be our own/our children’s advocates. If I hadn’t taken charge of figuring out what my tolerance really was I never would have made this discover, although the reason why I had to do the figuring out in this case is a blog for another day :|.

((Just to clarify my tolerance was 900 mg of phe. I admit increasing by 300 mg of phe was pretty ambitious, but this increase wasn’t nearly as insane as it would be for someone with a lower tolerance))


About Breamarie91

I am a twenty-three year old adult with PKU. I was diagnosed at nine days of age and have been treated every since. I also have two younger sisters who have PKU. In addition to studying early childhood/elementary education with a minor in creative arts, I also dance on my colleges dance team, work in a child care center and as a youth dance instructor, and function as the organization director of the PKU Organization of Wisconsin, Inc. I am also in the process of opening my own business (a dance

12 responses »

  1. Oh my goodness, yes. For me it wasn’t exactly due to the inaction of my clinic but personal frustration at the seeming randomness of my phe levels. There’s a back story I won’t go into, but I grew up being treated as classic PKU with a limit of 300. Well in college I blew way past that a lot and still didn’t have high levels, but because I was terrible about diet records my clinic never upped my intake. At some point I had gene testing done (one variant one classic)… and then just decided to eat whatever I wanted (for science, fully knowing the risks) for 3 days (still following most rules) and ate 800-1000 phe/day. My level came back at 8ish? So I knew something was up. My clinic was very accepting of my experiment and after that my levels were much more consistent. I feel maybe they’re just very cautious and prefer to leave it to the patient to make that decision? I don’t know. Thats a whole other blog post. Now I’m on Kuvan and kind of did the same thing to discover my tolerance is 35-40g protein. Still don’t fully understand, but hope to see more research in genotypes soon.

    • Glad to know I’m not the only one who discovered this! I just found it interesting, because a 300 mg of phe range is a really decent amount, and I never would have figured that out if I hadn’t been feeling rebellious and decided to up my intake on my own LOL!

  2. Bre I recently discoveres this to. My levels have been 2 lately and I’ve been eating 500 to 700mg phe so my clinic told me to focus on averages and when I send in my records they give me an average over 3 days and a blood result. I am tracking again for the first time in 13 years and adding up my own phe and calories in a note book agai. And I’m not stressed out or defeated. I feel like for the first time I havw things under control.  Best of luck and I love reading your posts!!

    Sent from Samsung Mobile

  3. I am a mom of a beautiful 2 year old with PKU. She was diagnosed at 4 days old. Her doctors have been very flexible from the beginning. Luckily she has always been very consistent with her levels in the 2 – 4 range. They always give me a number to shoot for and tell me that if she goes above by 50mg or so she should be fine. We try not to go to far below or her number will drop but using that range of 50mg has been really helpful. They also told us if we know she is going to have a high day (birthdays for example when she gets a regular cupcake) that we should just adjust her levels the rest of the week. Having that type of flexibility with a toddler who is still discovering new foods is wonderful.

    Thank you for blogging about this. As a worried mom, it is nice to see the success stories and know that my little one can have a very happy a normal adult life as she grows up.

  4. I had an opposite problem, I was ingesting 6 grams of protein a day (300mg phe) and sticking completely to it, however no matter what I did my levels remained 600-1000 (10-17). I couldn’t understand what was going on, I had just hit adulthood (18 here in NZ) and was trying to do things perfectly, I was even baking PKU foods once or twice a week. At the same time as becoming an adult, the support from my clinic immediately changed from 3-6 monthly to yearly. It’s a transition every PKUer in NZ has to make, but at the time it did seem harsh.
    In the end I gave up, I still ate low-protein but I didn’t count and barely bothered with bloods as I kept beating myself up because they were so high. Then after just under a year of not bothering I had a clinic and they got me to do a blood-test as, of course, they wanted to see how I was doing. Imagine my surprise when my levels came back at 400 (7)! Yes it was still higher then what would be preferably, but I hadn’t seen that number in over a year. I counted out my protein and I am now on 12-14 grams (600-840mg phe) with levels between 7-10. I aim in the new year to lower my protein intake slightly more (some days I could easily live off 7-9 grams protein or 420-540mg phe as I do a lot more PKU baking then I ever have in my life), in hopes that this will help bring my levels where I would like them.
    Ever since discovering my ‘new’ tolerance I haven’t bothered sticking to a single number, I aim to keep around a number, for example today, I have had 7 grams so far and will be eating another 2 grams for dinner and maybe another gram for dessert, does it matter that my quota is a little low, in my case defiantly not, lower can be better for my health, does matter if it goes a bit higher? To my mind at this point as long as my levels are below 10 I am happier, more easily able to manage my emotions, and less stressed about things and feeling healthier. That’s what is most important.
    Now my diet is very much self managed, with not a whole heap of input from my clinic team, but, I now know that if I need them, they are there for me, something I didn’t realize as a teen.
    I do admit I have trouble tracking my intake as it’s something to do for myself, recently I have been counting and keeping track over the course of a day with my partner who has become extremly supportive of me and my diet.
    Sorry for the super long reply!

  5. Hi Breanna, We also discovered this with our 4 year old son. Here in Australia we measure the amount of protein he is allowed to have per day. He was originally on 11 grams of protein per day. His levels since birth have always been excellent. We recently began a trial of Kuvan to see how responsive he would be. During the trial we tried to bump up his levels by giving him a phe capsule and then using Kuvan to bring it back down. The problem was we couldn’t get his levels to go up high enough so we had to give him more phe capsules before it was up to a level high enough that the Kuvan could bring it back down again. It turns out he is much more responsive to protein than we originally thought and he is now able to have 23 grams of protein per day without Kuvan, more than double what he was having before. His levels are a little higher than before but still within the safe range.
    The doctors at the clinic we attend were very impressed and have learned a lot from this. They are now looking to increase the protein allowance for other children on a case by case basis.

  6. My daughter Clare is 11, and at this point has been to 5 different clinics. Since she first started with dietary restrictions, we have always used a range for her, and never a specific number. Some of the best advice I got was from the dietician she saw in Iowa City, who told me not to drive myself crazy with hitting an exact number and a balanced diet every single day. Just to do my best, with the goal of a fairly balanced week.

    I also learned not to ever wait for the clinic to tell me what to do. If I think her levels are off, and we need to adjust, I tell the clinic what I want to do, and ask them if they are ok with it. I have never been told “no” yet 🙂

    Keeping in mind that Clare has a higher tolerance than most, her pre-Kuvan tolerance was 18-23g of protein a day. After she started Kuvan, we stopped testing her tolerance when we hit 45g of protein, because it was more protein than I could get her to eat. She’s now on a totally unrestricted diet (with no aspartame, of course), thanks to her Kuvan.

    • Hi Jennifer, it’s great to see Kuvan is working so well for you. Do you mind if I ask how many Kuvan tablets Clare is taking each day?

  7. My son has an extremely limited tolerance that can be as low as 150mg per day. He is not a Kuvan candidate. We have found that even he, with such a limited amount of PHE allowed, does okay in a range. Granted, his range is not very radical (150-200mg PHE per Day), but his levels have been much better than when we were sticking to a set rigid number.

  8. That’s nice you can have more Phe now! And I think you’re so right we always have to be our own advocate in health (I mean, within reason). I thought this was really interesting because my PKU clinic actually always gave me a range. Mine has been 400-600 mg for years. And I agree that if your levels are good, then you’re good! My levels are normally between 2 and 4. Once I visited China and did my best PKU wise – I came back and my levels were around 8, but my doctors said that was still safe. So I didn’t feel bad!

  9. Hi There! I am recent return to the PKU diet after years off & on the diet, I have found that I have a higher tolerance also through trial and error and on my own also..I am on 15-20mg natural protein plus three PKU express 20 (60mg of unnatural protein per day), I also take a tyrosine 1000mg sachet once a day. I am fairly relaxed with the natural protein as I have found my levels remain in the safe range even when I am so called “Cheating”..our bodies are all very unique and while it is the gold standard advice says to stick to the number given by clinic, we all have differing tolerances. I glad I have found out mine as it gives me the ability to be flexibile day to day and fit into whatever is going on in my life be study/out for dinner/tavelling or working…thank u Justine Inglis
    I have created a website about my pku journey .. xxx

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