A few nights ago someone mentioned Phenylketonuria (PKU) in a thread on AskReddit and I responded. Through the next few days I answered a lot of interesting questions. It was suggested that I do an AMA in case there are more.

PKU is a hereditary metabolic disorder in which the liver doesn't produce enough of the enzymes that break down the essential amino acid phenylalanine ("phe" for short.) Phenylalanine would normally be processed into tyrosine, but for individuals with PKU, the enzyme activity is completely nonexistent or diminished, and the increased levels of phe become toxic to the central nervous system. Treatment involves a very restricted diet, and a prescribed medical food that contains all the amino acids except phenylalanine. It is now accepted that treatment must be maintained for life; although in the past, patients were told to stop treatment during adolescence.

Phenylalanine is the main component of the artificial sweetener aspartame, hence the phenylketonuric warnings on gum and diet sodas. It is also present in almost every food to some degree.

Here's the TLDR of what we can/can't eat: No meat, no fish, no eggs, no milk, no tofu, and no nuts. Fruits, most vegetables, and some carbs are ok. Lots of special order foods are available as well. Protein comes from prescribed medical food (formula, "milk", protein shake) and has all the amino acids except phenylalanine.

I was born with phenylketonuria; diagnosed via Newborn Screening shortly after birth. I did not even taste meat until I was 28 years old and trying a new drug that helps keep phe levels in the blood low (in some individuals with PKU). AMA.

Proof has been submitted to the mods.

Edit: I'm heading to bed soon but wanted to leave a few points of data.

-Along with the dietary restrictions, one of our biggest challenges is dealing with the costs of the medical food and specialty foods. Each state in the US has different mandates regarding the ways health insurance companies must cover the medical foods. Insurance companies often claim we can buy it over the counter, therefore they will not cover it. I and others have spent countless hours on the phone explaining the situations over and over, submitting letters of medical necessity and having our specialty clinics call as well. This is the only part of having PKU that really gets to me.

-The only drug currently on the market is prohibitively expensive, even with insurance. One day of the pills can cost as much as one month of the medical food in some cases. This drug doesn't work for everyone. There are trials in process for one that will, though.

-If you or someone you know has PKU and needs support, please visit one of the websites below and/or look up support groups online. There are a lot on facebook (just search for pku or phenylketonuria), and here we can be found at /r/phenylketonuria

http://www.npkua.org/ United States

http://www.canpku.org/ Canada

http://www.espku.org/ Europe

Comments: 48 • Responses: 21  • Date: 

hulone11 karma


mermaid-out-of-water10 karma

I tasted bacon for the first time a little over a year ago and hated it because it was chewy and weird. Then someone in my husband's family carefully selected choice pieces of freshly cooked bacon and then I understood. Before the new drug I would not have touched it, but now I will eat a piece or two once in a while in a breakfast taco or BLT.

My life doesn't feel limited aside from at mealtimes. My family had an "It is what it is," attitude and I grew up with it being a fact of life, and not something to feel sorry about. I have to plan ahead very carefully when attending business dinners and traveling. When I travel I have to take all my medical food and meds in my carry-on bag, as well an a current letter of medical necessity. Travel lasting over a week gets fussy because the medical food cans take up so much space, but I love to travel so I just deal with it. I research the local cuisine and learn how to order safe foods ahead of time and really just try not to let PKU run my life. Same with going out: I look up the restaurant's menu and plan ahead.

The specialty foods can be very expensive. Bags of pasta are around $10 USD, a loaf of bread $13, a 6 lb tub of baking mix is $35. Shipping can get expensive too. A lot of us try really hard to survive on what we can buy at local grocery stores. The emergence of coconut and almond milk products has been wonderful for us, as has the influx of gluten free products. We can't eat all of them, but many are safe for PKU.

My favorite food is avocado sushi. I love to cook and bake cookies.

I heard about Soylent on the radio a while back. I admit at times I wish I could just drink a shake and not even deal with food, but I love to cook too much!

hulone6 karma


mermaid-out-of-water4 karma

Thanks, I'll check it out!

I am currently taking the new drug. It increased my phe tolerance significantly, but I can still only handle a bit less than half what a non-pku person can.

MrGross11307 karma

When I was younger I liked to call customer service numbers from food I ate to ask stupid questions. One of those products was Listerine strips. I asked them what phenylalanine was and if I should be worried about eating it. Finally life tells me what it is. Thanks dude.

YouAreAllBitches1 karma

I used to call one number from a commercial and ask a bunch of questions about a product from another commercial. I was the one who could keep a straight face and keep asking about the food dehydrator when I called the number for The Neptune Society. I soon realized that sometimes they were, in fact, the same company selling different products. But, not in that case.

MrGross11303 karma

I was the one who called Coke and asked where to find gravy flavored soda

mermaid-out-of-water2 karma

Doesn't Jones soda company make that one?

itscoredawg5 karma

What is tyrosine?

Also, what are the side effects of PKU? What reactions do you get when eating food containing phe?

mermaid-out-of-water5 karma

Tyrosine is a component of neurotransmitters like dopamine and epinephrine. It is my understanding that it is basically a common building block in proteins, and plays a role in hormone balance, mood, and pigmentation. If a person with PKU isn't following the treatment and phe isn't being processed into tyrosine, their hair and skin can become pale.

If I overdo it on phe, the effects are irritability, depression, and general physical discomfort for a few days after. Some people also experience mood swings, some have headaches; it really varies. Long term effects of non-compliance include neurological issues, constant headaches, eczema, hyperactivity, lack of energy, and all kinds of anxiety and depression symptoms. Regarding the anxiety and depression, many of us who have never gone off treatment are hyper-sensitive to those feelings because we are always afraid we accidentally screwed up and didn't realize it (cue MORE anxiety.) We have to remind ourselves that just because we have PKU doesn't mean we are exempt from other illnesses.

Scottie_Nippen2 karma

I also have PKU, this is one of the best descriptions of the physical effects of having high blood-Phe levels.

In my case, if my blood levels are a bit elevated (which they are now, curse you IHOP and your delicious pancakes) I tend to feel fatigued and just generally uncomfortable. As the Phenylalanine saturates the blood-brain barrier (where most neurotransmitters are transferred), it begins to inhibit other essential transmitters, like /u/mermaid-out-of-water said. At least in my case, I can notice a slight tremor in my fingers and toes, and I feel very "jittery." These effects vary in severity, but usually only last about a day if I get my levels under control again.

If you don't mind me asking, /u/mermaid-out-of-water, what formula are you on? I'm currently taking Phenyl-Free 60, just because it's the most concentrated and has the highest protein equivalent per gram.

mermaid-out-of-water3 karma

IHOP's hash browns always cause me trouble. :P

I drink phenylade 60 vanilla. I drank phenylade MTE for years though, because I could mix it with pretty much anything on hand, but recently I just want to add water, shake, and chug. Get it over with. Before that I drank PKU3 mixed with fruit juice, which was horrific.

twistedfork1 karma

/u/mermaid-out-of-water covered a lot of side effects, but before newborn screening, PKU was like the largest cause of mental retardation in children.

mermaid-out-of-water1 karma

Wow I didn't realize that!

One of my mom's cousins has PKU but she was diagnosed as an adolescent and is now a ward of the state. My mom works with special needs adults and there are apparently quite a few elder adults with PKU whose parents had to sign them over to the state.

twistedfork1 karma

It was almost definitely because of undiagnosed PKU as a child. I work for the Oklahoma Dept of Health and we do newborn screenings for 10 metabolic disorders and PKU is one of them. I was talking to someone that works in that division and they said the rates of mental retardation dropped by a measurable percentage when they identified PKU.

Additionally, if someone wobbles in and out of a low protein diet, they become more and less er...mentally delayed? Testing shows that their cognitive abilities are directly related to diet and reversible if the diet is corrected soon enough.

mermaid-out-of-water1 karma

Amazing what newborn screening has done.

Different people have different tolerances for "cheating" but generally one or even a few days of it can be repaired, but longer than that and repairs become more difficult. Admittedly I don't know the exact cutoff, but the stat they throw at us in clinic is (I believe) ten IQ points lost for each year "off diet." I'm sure it differs based on severity of diagnosis, and probably developmental age.

gburgballer163 karma

My best friend also has PKU, and so does his sister. I've tried the formula and it tastes sooooo nasty. Here are my questions for you: Do you ever break the rules? My friend will constantly, although none if the foods he eats has all that much protein in it. Also, do your friends poke fun about PKU? For instance, I made signs for my friend for his high school soccer games just saying "PKU" instead of his name. He also snapchats me videos of him eating grass... Thank you!

mermaid-out-of-water3 karma

My formula isn't too bad (plus I just chug it without thinking these days) but there are definitely some out there that are pretty pungent.

When I was a kid I didn't know any better than to eat within the rules, but as a teenager I definitely ate more french fries than I was allowed. In college I chilled out and got everything figured out though. Once in a while I'll splurge on a meal, but because I really feel the effects, I don't like to do it. No food is worth feeling like I can't do my job or talk to people without fussing.

When I was in elementary school I was definitely bullied, but after switching schools in 6th grade I wasn't. I became the token vegetarian of the group. Friends now have some amusing commentary once in a while but it's usually along the lines of whether or not I'd be a target for zombies in case of a zombie apocalypse. I wouldn't hang out with anyone who was actually mean about me having PKU. I definitely use humor to cope so I appreciate a good-hearted jab.

grunt_stick2 karma

How common is your condition? Having read enough 'food product' labels, I've seen the warning about phenylalanine on a variety of artificially sweetened items. Is there a high incidence of PKU in the general population?

mermaid-out-of-water3 karma

In the US the incidence is 1:15,000-20,000. It is somewhat more or less common in European countries, around 1:2,000 in Turkey, and I'd have to look up the rest. It is actually found worldwide, but many people believe it is only found in Europe, Canada, the US, and Australia. There are cases in South America, Africa, the Middle East, and Asia as well.

Because I am very active in the community, I know (mostly through Facebook) over 100 people with PKU worldwide. Unfortunately many people with PKU grow up feeling alone because local support groups are few and far between. We are working on that, though.

misskitty50772 karma

Thank you for doing this! I have always wondered what the warning was all about but never bothered to google it. :)

mermaid-out-of-water1 karma

Glad to be of service. :)

dexigo2 karma


mermaid-out-of-water5 karma

That sounds like some bizarre PKU zombie infestation scenario.

FranklyAsh2 karma

Do you have to drink those formulas for dietary supplement. If you do, have you had any success in getting it covered by insurance?

mermaid-out-of-water2 karma

I do have to drink one, yes.

My current health insurance company actually covers it, but in the past (with other companies) I'd have to fight over it. I basically had to tell my current one where to find the text that states that they do, in fact, cover it though.

ettenyl2 karma

I am a dietitian at a facility with a mentally-disabled person with PKU (was born prior to when they started testing at birth). I've been searching for a formula for him for a while now that'll be covered by insurance and not taste like shit. Any ideas? I've tried phenex-2 just because of the higher calories but good lord it is terrible tasting.

mermaid-out-of-water2 karma

Have you looked into any from the Phenylade line from Applied Nutrition? Their Essentials flavors and 60 vanilla are both favorites of mine. I've had the best luck getting them covered so far. YMMV due to state regs though.

ettenyl2 karma

I'll look into it, the state is weird about what they will/not cover. I liked the Glytactin by Cambrooke but it wasn't enough calories compared to other options.

mermaid-out-of-water2 karma

I would love to switch to that for health reasons but I can't stand the aftertaste. It is literally the ONLY formula I will not drink. I feel bad about it, too because I personally know the owner of the company and she works SO hard on these things!

userjjb1 karma

I would love to switch to that for health reasons but I can't stand the aftertaste.

Is this the Bettermilk or Restore? (see my comment above to ettenyl) The Bettermilk has 3 different flavors too: regular, strawberry, and orange. Their recently was a reformulation of the minerals that eliminates the aftertaste you are talking about.

It might be worth getting samples of the improved product and see if you like it.

mermaid-out-of-water1 karma

Bettermilk. Restore tastes fine but it's just so much to drink. I tried the new bettermilk flavors at a pku event a few weeks ago and was pleasantly surprised. Those Complete bars are great, but I don't think I could eat one every day.

ettenyl1 karma

Just ordered samples. Thanks for the suggestion!

mermaid-out-of-water2 karma

I actually crave the orange cream flavored one sometimes!

It seems that the more calories it has, the better it is covered. Coverage is now often based on calorie content instead of something that makes sense like protein content. I understand the reasoning but do not agree with it. :/

emradio2 karma

What is a typical meal like for you? Is it really difficult to eat out with friends?

mermaid-out-of-water8 karma

I eat a LOT of vegetables and a little starch.

Breakfast is fruit and a little oatmeal - or a tortilla, an egg white, and ten grams of shredded cheese. Before the new drugs I had trouble eating breakfast unless I'd had time to bake something from scratch because I don't like the lower-protein cereals.

Lunch and dinner are mostly cooked vegetables and salads. I can eat rice and potatoes without too much moderation now, but before the new drug I had to limit them.

I count myself lucky that I grew up in a city that was full of good veggie options anyway, but I definitely fell into salad-and-fries ruts all the time. The discovery of veggie sushi and stir fry changed my life.

TerporDie1 karma

I'm glad you did this IAMA! My question: WHAT?!? YOU'VE NEVER HAD MEAT? How do you live? Dude I'd totally die if I couldn't have bacon. Hahahaha. Story of our lives!

mermaid-out-of-water3 karma

I can't tell you many times I've heard "I'd DIE if I couldn't eat meat!"

No you wouldn't you, precious little snowflake. You'd adapt and you'd live. :P

MamaD_Cooks1 karma

Whoa, $13 for bread? Have you thought about making these things yourself? What is in bread that you can't have? My typical recipe is just water, yeast, sugar, olive oil and flour.

mermaid-out-of-water2 karma

I do prefer to bake my own. We have baking mixes that are modified to be low in phenylalanine. They're expensive, too, but make baked goods so much better.

Flour has ~8g protein per serving, and someone with classic PKU may only be able to eat 6-8g protein from food per day.

BlahHorsey1 karma

This is all so interesting! Are there any foods that you've really wanted to try (because they look tasty or smell great) but haven't been able to have yet?

mermaid-out-of-water1 karma

I think I have tasted everything I could think of, but the one thing I can't eat but would like to, is edamame.

leannebrown861 karma

I have a mild form of PKU, Hyperphenylalaninemia. This hasn't affected me until I started to plan a family. My levels do not and have never affected me or my development (lots of tests every year during childhood) However when planning to get pregnant I must follow a strict low protein diet and take supplements, in order to protect a growing baby from high phe levels. I was wondering if you had heard of this form of PKU as I've yet to find anyone with the same condition. Also do your levels impact you when planning a family in any way?

mermaid-out-of-water1 karma

Yes I've heard of hyperphe. I actually know some people with it. Do you use any online support groups? There are a bunch on Facebook, including ones geared towards pregnancy and PKU, and hyperphe. If you want a non Facebook maternal PKU group I will try to find the link. A really great group of women run it.

When I decide to have kids I am instructed to keep my phe levels between 2 and 4 for a few months before starting ttc, and then throughout the pregnancy.