Miso butter potatoes and veggie pineapple tacos headline a free cookbook aimed at helping COVID-19 long-haulers enjoy food again after losing their sense of taste and smell

• Some people who get COVID-19 develop lasting symptoms, like loss of taste or smell.
• A new cookbook was formulated specifically to help coronavirus long-haulers enjoy food again.
• The book, "Taste & Flavour," is available for free as a digital download.

For coronavirus long-haulers, loss of taste and smell is one of the persisting symptoms. Now, a new cookbook aims to help those people enjoy food again.

The book, "Taste & Flavour," features 18 recipes with stunning food photography and is being offered for free as a digital download.

UK Chefs Ryan Riley and Kimberley Duke spent months formulating the recipes, designed specifically for people experiencing an altered sense of taste and smell due to COVID-19.

"If you're living with taste loss no one talks about it," Riley told Insider. "But six months of not being able to taste something and you form a mental barrier to food. It can become a mental health problem in itself."

Researchers estimate about 10% of people who become infected with COVID-19 become long-haulers, meaning they have symptoms that last for months and for some, indefinitely.

A quarter of people who experience an altered sense of smell or taste improve within a couple of weeks, according to John Hopkins Medicine. But for most, the symptoms persist and some have gone more than a year without improvement.

Riley and Duke, who run a cooking school for cancer patients experiencing loss of taste, spent months working on the recipes. They consulted with Barry Smith from the University of London's Centre for the study of the Senses, a leading UK researcher for loss of smell as a COVID-19 symptom.

Riley said about 80% of taste is actually smell, so the two senses are considerably intertwined. Some COVID-19 long-haulers experience anosmia, a loss of smell or taste, while others experience parosmia, a distorted sense of smell.

Creating the recipes for the book involved heightening certain flavors while avoiding others. Coffee, for instance, can smell like sewage to some people with parosmia. Things like onion, garlic, eggs, roasted meat, and nuts can smell "repulsive, almost like rotting flesh," Riley said.

"It's quite hard to write a recipe without garlic and onions," he said. "They're the basis of flavor."

Instead, the chefs focused on amplifying the savory flavors and "adding texture and brightness to make up for the lack of depth."

Riley and Duke tested nearly 300 recipes to narrow them down to the 18 that made it into the book.

They relied on intense savory flavors like soy sauce, miso, parmesan, and mushrooms, and tried to touch on all five basic tastes - sweet, sour, salty, bitter, and umami - and stimulate all the senses. They also used ingredients that stimulate the trigeminal nerve, which is responsible for sensations in the face and sinuses and can be felt when eating foods like horseradish and wasabi.

Riley called the miso butter potatoes with green herb vinegar the "perfect" recipe in that sense. The potatoes are umami-rich. The miso and soy sauce are umami and salty. The white pepper and fresh mint stimulate the trigeminal nerve. The green chile adds crunch for texture. The vinegar sets off the sour receptor.

Even though it seems like a simple recipe, Riley said, "it's actually designed to stimulate all of the senses and a lot of the different taste buds, but also has to taste really nice."

Riley said the reception to the book has been incredible, with people from around the world reaching out to thank them.

"Flavor is important. I think that's what we're desperately trying to make people understand," he said.

Riley and Duke started Life Kitchen, their free, nonprofit cooking school for cancer patients, after both had lost parents to cancer.

"I'd seen my mother go through all of the sadness and pain of not being able to eat," Riley, who lost his mother to cancer at age 20, said.

In 2017, he first had the idea to do a one-off cooking class for cancer patients whose taste had been altered by the disease or the treatment. But after a tweet about the class went viral, they launched Life Kitchen as a full-time endeavor.

"It's depressing if you can't taste," he said. "It's one of the biggest pleasures that we all take in this world. If you take that away, life really becomes a diminished experience."

Have a news tip? Contact this reporter at kvlamis@insider.com.