Many of us in pursuit of wellness (or weight loss) have tried a restricted eating plan at some point, be it the Mediterranean, South Beach, or Cabbage Soup diet.

We give up sweets, carbs, and sometimes solid food, and it works — for a while. Then eventually we blow it on a slice of cheesecake or a slab of home-cooked lasagna.

But what if you had to go on a diet from birth and could never cheat or take a break?

What if you could never savor a juicy steak, a piece of salmon, or a slice of pizza?

What if your life literally depended on sticking to your diet?

The diet that never ends

Tyler Garner eats french fries for dinner every Tuesday supplemented with a bottle of formula. Sounds a bit high in calories and low in nutrition for a toddler, right?

But Tyler isn’t a toddler. He’s 18 and has a rare metabolic and genetic disorder called phenylketonuria (PKU). French fries are one of the few listed foods he can eat safely, although it doesn’t fuel his dietary needs, hence the formula.

The formula Tyler drinks is part of what keeps him alive. With PKU, your body can’t break down phenylalanine, an amino acid found in protein and most foods.

PKU symptomsMild to severe PKU symptoms include seizures, tremors, stunted growth, hyperactivity, skin conditions, and bad breath or body odor. For people with PKU, if their diet is managed properly during childhood, it can prevent symptoms from showing and potential cognitive disabilities from developing.

People with PKU can’t eat foods like hamburgers, steak, fish, ice cream, cheese, or milk. Even worse, they may be hungry all the time from a diet that’s neither nutritious or satiating.

Because of the restrictive and emotionally exhausting nature of the PKU diet, 70 percent of teens and adults living with the disorder go off or avoid it.

It’s a gamble with a poor payout.

While less serious side effects of PKU include headaches, anxiety, and poor cognitive functioning, a buildup of phenylalanine can be extremely dangerous and going off the diet may cause irreversible brain damage.

Erin MacLeod, a genetics metabolism expert at The Children’s National Rare Disease Institute in Washington, D.C., counsels and treats PKU patients who are usually referred to her after the results of newborn screening.

"I remember thinking early on, ‘this is so much’ but you just want to do the best by your child. You learn [about PKU] and you learn it fast. You become an expert." – Allison Reynolds

“We work with the National PKU Alliance to teach children and families to accept their condition,” she says. “They can’t eat like their peers, and must drink a bad-tasting, strong-smelling prescription formula containing the amino acids they can process, three times a day. The good news is, if PKU patients follow a strict diet, they can live a long and normal life.”

Allison Reynolds, recalls the moment she found out that her now 15-year-old daughter, Tia, had PKU.

“When I found out, I was shocked. I was angry – I threw the phone across the room. I cried a lot. As a parent, you mourn your old expectations and begin to develop new expectations for your child’s life. It’s already hard with a newborn, but PKU can make it much more complex. I remember thinking early on, ‘this is so much’ but you just want to do the best by your child. You learn [about PKU] and you learn it fast. You become an expert. In those early days, I spent so many nights in a row reading about PKU and what it meant for my child.”

But knowing exactly how to help your child doesn’t necessarily make living with PKU any easier. Kids struggle on the diet because they want to be independent, maybe even going for a hamburger with their friends.

“They can never get a break,” says Reynolds, who is involved in advocacy efforts, such as fundraisers, like Lifting the Limits on PKU. “The only foods Tia can eat are vegetables with special low-protein rice, vegetarian soup, or low-protein pasta with vegetables and fruit. Between blood draws and managing her intake — four grams of protein is the maximum and that’s found in one slice of bread — it’s hard work.”

"When he’d drink the formula during lunchtime, kids commented on its funny smell. I told him he still had to drink it. During middle school, he came home for lunch to drink his formula." – Jennifer Garner

Jennifer Garner, Tyler’s mother, agrees with the effort involved in diet management. “When Tyler started kindergarten, I got the school to refrigerate his formula. For parties, I would supply premade cupcakes.”

Garner tried to put a positive spin on Tyler’s condition so he didn’t feel bad. “I said, ‘You’re so lucky you have PKU and not something worse. And, it’s great you’re a vegetarian because they live 10 years longer than meat eaters.’”

But she admits that other kids weren’t always so supportive.

“When he’d drink the formula during lunchtime, kids commented on its funny smell. I told him he still had to drink it. During middle school, he came home for lunch to drink his formula.”

Moving into adulthood with PKU

Despite the hardships Tyler has encountered, Garner feels optimistic about her son’s future.

“I’m not concerned. He thinks meat is weird and dairy is gross. My worry is that he might forget to drink his formula and become disorganized or frustrated. But, I have confidence he’ll eventually figure it out. I’m excited for his future and so is he. We’re all dealt different cards. And this is his.”

As a teenager, Tyler recognizes that his parents are just trying to help.

“I think it is normal for a family who has been affected by PKU to always make sure their kid has drank their formula and stays on diet, but that in turn can make it difficult to feel independent at times,” he acknowledges.

“I always try to take a step back and try to realize they are just trying to make sure I stay healthy. I always tell myself I’d rather them care too much than not enough.”

“Although people have good intent, things like that can make kids feel singled out or like they are placed an unwanted spotlight. But, although PKU is hard, it’s not the end of the world.” – Tia Reynolds

Reynolds is also dealing with the budding independence of her teen.

“If she doesn’t stay on the diet, she can get headaches, become unfocused, unstable and anxious. All of that can lead to depression.”

“When Tia moved to a new school for high school, before she had a chance to educate the kids on PKU, a boy threw her lunch in the trash. Now she goes to eat out with her friends a lot more.” Fortunately, for the most part, her daughter hasn’t faced too much bullying when it comes to her condition.

“However, I don’t know if I can say the same for everyone,” Tia says. “Unfortunately, many people just don’t understand. One boy at school asked me every day what I could and couldn’t eat, and why I carried a lunchbox. Although people have good intent, things like that can make kids feel singled out or like they are placed an unwanted spotlight. But, although PKU is hard, it’s not the end of the world.”

“The hardest challenge is the fact that, when going to school or dinner with friends, you’re always isolated from your peers. You can’t eat what everyone else is eating. PKU is also difficult because not a lot of people know about it - it’s rare, so many people don’t understand it that well.”

She has found a way to manage her PKU that works.

“If you hold yourself accountable and start taking care of your own Phe levels, that’s a good way to become more independent. For a while, I didn’t have a great roadmap of every food item and how much protein it contained, but now I have a better understanding of how much protein is in things. It makes it easier to go out to eat with family and friends and feel normal.”

Reynolds is also optimistic for the future. “A federal bill has been introduced to get insurance to pay for formula and low-protein foods,” she says.

“Also, one drug currently in the pipeline would be a self-administered subcutaneous injection in the hip or stomach like insulin. With a cure, everything would change for my daughter. Even her ability to have children.”

Until there is a cure, as both Garner and Reynolds know, finding a cure for PKU is a matter of life — and diet.


Estelle Erasmus is an award-winning journalist, writing coach, and former magazine editor-in-chief. She hosts and curates the ASJA Direct podcast and teaches pitching and personal essay writing for Writer’s Digest. Her articles and essays have been published in the New York Times, Washington Post, Family Circle, Brain, Teen, Your Teen for Parents and more. See her writing tips and editor interviews at EstelleSErasmus.com and follow her on Twitter, Facebook, and Instagram.