I Tried the PKU Diet for a Day Challenge and It Was Nothing Like That Time I Was Vegan in College

The National Society for Phenylketonuria (NSPKU) is holding their PKU Diet Challenge today. The diet challenge is specifically aimed at MPs (Members of Parliament in the UK– aka, not me), but anybody is invited to try it out in solidarity with the PKU community. I don’t have PKU, but I wanted to try the challenge to better understand the unmet needs the PKU community faces. I participated a day early, so that anyone trying it today could check out what helped me and where I made mistakes.

What is Phenylketonuria (PKU)?

Before I launch into the rules of the PKU Diet Challenge, it’s important to first understand the background. PKU is a rare, genetic, metabolic disorder that prevents the body from processing an amino acid called phenylalanine (phe). Since people with PKU can’t break down phenylalanine, it builds up in their system, which causes serious health complications.

The symptoms of PKU include, but are not limited to, seizures, developmental delays, decreased bone strength, microcephaly, skin rashes, odors, and heart defencts. PKU can’t be cured, but it can be managed– especially if it’s caught early on. The treatment includes avoiding foods with phenylalanine, monitoring phenylalanine in the blood, and taking supplements to help make up for the restrictive diet. The thing is, phenylalanine is in almost all foods with protein (meat, eggs, nuts, beans, whole grains, you name it), as well as artificial sweeteners like aspartame.

Of course, everyone needs protein to build and repair tissues, create enzymes and stay healthy, including people with PKU. After eating a very low-protein diet, patients need to consume formulas and special medical foods that give them protein with phenylalanine removed. There is also a medication called Kuvan, which helps reduce phenylalanine in the blood. Many patients say the formulas and medical foods don’t taste great, but they eat them since they’re crucial for staying healthy. This can be pricey, and various groups are working to make sure this treatment is accessible to all patients.

What are the rules?

You can check out the rules here, or visit the NSPKU site here, so I don’t want to spend too much time explaining them in detail. Essentially, the goal is to eat under 10 grams of protein a day, following a traffic light system resource from the NSPKU. Meat, soy, and other classic high protein food are given a red light, since you can’t really incorporate into a PKU diet. The amber list is full of foods can be eaten with caution and diligence, like potato, corn on the cob, breakfast cereal, and kale. The green-light low-protein foods include most fruits, various vegetables, avocados (!), sweet potatoes (!!), most oils and fats, jams, coffee, and a few other things.

Challenge participants are not expected to go through the blood tests that PKU patients do, or consume the protein supplements. They are, however, expected to weigh food on a digital scale that can measure food down to the gram.

How I broke / modified the rules from the start

The truth is, I don’t own a digital scale. I tried to be as exact as I could, by using measuring cups and counting out exact portions of tortilla chips, but it wasn’t perfect. If I really had PKU, I wouldn’t be afforded this leniency.

I also modified the protein supplement rule: PKU protein substitutes and prescription foods weren’t part of the rules, but I didn’t want to risk taking an actual toll on my health. I know that might be a little dramatic, but since I have a somewhat hard time incorporating enough protein into my diet as is, the idea of intentionally removing it made me uneasy. Instead of drinking the prescribed protein supplements, which I don’t have access to, I drank a non-PKU-friendly protein drink. This isn’t something I enjoy, so I thought it was the best equivalency I could come up with. I have, however, been told that the PKU drink tastes a lot worse.

I also want to say up front: *Spoiler Alert* I didn’t quite make it under 10 grams, even though the whole irony of this challenge is that that’s actually a generous protein allowance for someone with PKU– many people only eat a fraction of that. I ate the lowest protein diet I knew how to, but I did pass the limit. Although I wish this could be an article about success, I think it’s also important to talk about why this didn’t work, and the challenges people who follow a PKU diet every day face.

“The vegan thing”

If anyone from the PKU community wants to roll their eyes at me for bringing up plant-based diets, that’s totally fair. It was naive and ignorant, but I had thought that, as a lifelong vegetarian with a three-year vegan stint in college, I was already coming in with some understanding of the PKU diet. Of course, I knew the scale was different: I never had to measure food, just avoid animal products, and plus, I was doing it totally of my own accord. If I accidentally ate an animal product, the worst case was I got a temporary stomachache, not permanent neurological damage. But, I was familiar with reading labels, eating strange alternative cheeses, bringing Tupperware of Earth Balance butter to Panera, scanning menus and realizing there was nothing I could eat, feeling a little isolated, feeling like my diet was a burden on the people around me. I want to clarify for anyone from the plant-based community who might be under a similar misconception, these are two experiences that cannot be equated: as a vegan, I lived a life full of peanut butter, chipotle bowls, and Oreos. I never had to worry about hunger, measurements, or developing serious health problems.

The grocery store

I prepared for the challenge by going to Aldi the night before. Therein lies my first mistake. If your town is not blessed with an Aldi, it’s a discount grocery store. It keeps prices low partially by limiting selection. While a larger store might contain alternatives like vegan cheeses and low-protein bread, Aldi mostly only caters to people in the center of the bell curve, people with the most typical diets. I realized that people with PKU already know this: not every grocery story is equipped with the food that they need for their daily lives.

I knew sweet potatoes and avocados would be central parts of my PKU diet challenge, since they both contain a fair amount of sustenance for a green-light item. I also wanted a snack, and spent way longer than any normal human in the cracker/chip aisle looking for the lowest protein option. Sometimes I would see “Protein: 1 gram,” on a box of crackers, get excited, and begin to put down the other 2 gram protein bag of tortilla chips I was holding. Then I would see it: 1 gram protein crackers only had 70 calories per serving, while protein 2 gram chips had 140 calories per serving. So they were the same.

This basically sums up how I felt most of the time I was shopping: yes, I could find food with very low protein, but those foods were also very low calorie. If I wanted to feel full and have enough energy for a regular day of walking, working, and exercising, I would have to eat multiple servings of each item– and suddenly, the low-protein foods weren’t low-protein anymore.

I thought about the scene in A Cinderella Story, where Mean Girl Shelby comes to the diner where Hillary Duff works and asks, “What can I get here that has no sugar, no carbs, and is fat free?“ and Hillary Duff gives a cheeky eye roll and is like, “water,” except this time I felt like Shelby was actually the relatable one in the situation– just a gal looking for food that fits her dietary needs, but isn’t literally void of nutrition or substance.


I want to emphasize that breakfast is very important to me. I usually wake up starving, eat a huge meal right away, and then a smaller lunch. I’m also not a believer in the arbitrary category of breakfast foods, and am happiest when I start my day with a bowl of pasta and veggie meatballs. 

For my PKU challenge breakfast, I began with hor d’ouevres of a Honeycrisp apple cut into slices (by which I mean, I was too hungry to wait while I cooked).

My main course was an entire sweet potato (it’s on the green list, but a whole sweet potato contains 2 grams of protein), sliced up and cooked with a little garlic and salt, 3 white sauteed mushrooms, two tablespoons of pico de gallo, the smaller half of an avocado, and a little sriracha. I also had 7 tortilla chips, which added 2 more grams of protein. Breakfast was overall an enjoyable meal– it’s a lot like something I would eat on a normal day, minus rice and beans.

Besides the tortilla chips, everything I ate was on the green-is-go list, so I was surprised when I plugged my meal into My Fitness Pal on my phone and saw that I had already racked up 6 grams of protein.


I had some wild dreams of cooking up a whole fancy mid-day meal with rice vermicelli noodles (a naturally low-protein option), but when noon came around, I didn’t feel like I had time to make a real lunch. I sliced up the second half of the avocado from the morning, one roma tomato, and added a little Kim Kim hot sauce and salt. I ate this on five whole wheat Ritz crackers (1 gram of protein), which was, you know, okay. Essentially, lunch was the sadder, lazier, version of what I had eaten that morning, plus 5 baby carrots I grabbed while running out the door. I had thought I was doing a decent job– I had eaten almost exclusively green list items, but when I calculated it, I had already reached 10 grams of protein. Although calorie recommendations vary from one person to the next, it’s generally encouraged that adults consume no less than 1,200 a day. Since I was tracking my food for the day on My Fitness Pal, I knew that I had only reached 760. This would be a problem: I wasn’t able to meet my caloric needs for the day without surpassing my protein allowance. I later read that not every source of protein counted the same: for example, the protein in an apple doesn’t include as much phe as it does other amino acids, which is why it isn’t included as a whole exchange. I started to try to calculate my real PKU protein exchange score, something that some PKU patients use apps for.

I drank a vanilla protein shake as my substitute for a protein supplement. Although I generally dislike protein drinks (I find them powder-y and they make me feel like I’m living in a colorless dystopian future), it wasn’t actually too bad. I’ve never had a PKU protein formula, so I can’t compare the taste (although if anyone wants to send me protein formula so I can roast it on this fake food blog I am apparently starting right now with this article, message me) (don’t really do this if you need the PKU protein formula to live!!). From what I’ve read though, they aren’t something basically anyone would voluntarily drink. I also had a PKU-approved black iced coffee.

Although sweet potatoes, avocados, and other vegetables, are classic health foods, they also have a ton of fiber. I started feeling less like an Instagram health model and more like a girl who might need a Tums in a few hours. *Immediately google searches: Are Tums PKU-friendly?*


By dinner, I was hungry, but I couldn’t afford much more protein. I couldn’t find low-protein pasta at the natural foods store, which I had such high hopes for. So I settled for butternut squash noodles with tomato sauce and two sautéed mushrooms. Butternut squash pasta doesn’t have much protein (it’s considered a free food that doesn’t have to be counted towards protein exchanges), but it didn’t have much of anything else either (80 calories for this whole plate). My total for the day was 11.5 grams of protein (plus the protein shake), although most of the sources I ate were on the low phe end of protein. Maybe if I had calculated it out factoring in for foods that were low in phe, I could have come in under 10 grams. However, I was tired, hungry, and cranky. After about 25 minutes of cross-comparing protein charts and looking up gram to ounce ratios and brushing up on my long division, I realized the big problem was that I really, really didn’t want to do this. I accepted defeat. I had lost the challenge. While people with PKU are undoubtedly better and more efficient than I am at figuring out how much phe they’ve eaten, I’m sure there are times when they, too, are tired, hungry, cranky, and really, really don’t want to keep track of the food they ate that day.


The big take-away

The PKU diet is tougher than most people understand, and definitely tougher than I understood. I could have prepared better for the challenge by speaking with a dietitian or ordering low-protein alternatives online, but I think there’s something to be said about learning that eating under 10 grams of protein with only access to an Aldi is very, very hard. Some PKU patients also have difficulty accessing specialized foods and formulas, and that’s a serious problem when you take into account the symptoms they risk if they eat the wrong food.

It’s also hard to comply to. I went to bed still feeling a little hungry, and that was okay. I can wake up and eat exactly the way I always have, but a PKU patient never gets time off. It’s not like a diet with a once-a-week cheat day; it’s every day, forever. Some PKU patients speak about hunger and lack of energy as a problem. A lot of people with PKU also just want to different types of food. I have said many times that I don’t like protein shakes (only referring to the typical, sweetened grocery store kind)– many people with PKU struggle to drink the bitter PKU formula, and many parents spend hours trying to get their kid with PKU to drink it. This largely synthetic diet can take a toll on a patient’s health.

Additionally, it’s isolating. I was okay– I work from home, so I have a lot of freedom when it comes to preparing all three meals in my house on my own time. Had I been meeting friends, traveling, or going out to eat, it would have taken a lot of work to eat safely. There are a million other ways the disorder is tough, but if you’ve read this far, you already know that.

I realize this diet is both harder and easier than what I experienced. People who have PKU are pros at this in a way that I am so very obviously not. If you’re on any special diet, you learn tricks and discover treats that fit within your limit. You follow blogs for meal inspiration; you stock up on special ingredients that I don’t have in my home; you learn how to make your favorite meals in a new way. At the same time, people with PKU have to comply to the diet every day an miss a lot of the social aspects of food. Patients with PKU face anxiety that what they need to survive might be taken away– Americans with PKU battle their insurance over medical formulas or low-protein foods, while patients in the UK struggle with problems with NHS prescriptions.

Groups like NSPKU help the patient community face these hurdles through different initiatives. If you’d like to learn how you can support them, check out their page here.

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