Having been little more than an afterthought in the history of the limited-service restaurant industry, plant-based proteins today are increasingly becoming an integral ingredient in many menus. Led by a desire for sustainability and more healthful eating, Americans are discovering they can get plenty of protein without eating meat or seafood.

While vegetarians and vegans are a big part of this growing interest in plant-based proteins, analysts say they are only a small reason for it. According to a Harris Poll commissioned this year by the Vegetarian Resource Group, just 3.3 percent of Americans are vegetarians, and just half that are vegan. That’s virtually unchanged since 2012.

The poll reveals there has been a fairly substantial increase in younger people, particularly millennials, seeking more plant-based meals at least once a week. Both analysts and restaurant operators echo that finding.

“When it comes to specifically seeking out plant protein, 37 percent of consumers ages 25–39 do so, whereas just 20 percent of all U.S. adults do,” says Elaine Tecklenburg, an analyst for Packaged Facts, pointing to a study by the research company.

Having a plant-based ingredient as the protein in a menu item “is appealing to a younger age group,” says Michael Stebner, culinary director at Sweetgreen, which has more than 50 units. He contrasts younger diners’ ease in ordering alternative proteins to baby boomers “who come in and have a salad with chicken because it’s comfortable and approachable to them.”

There are plenty of reasons plant-based proteins appeal to a younger demographic.

“Millennials have a greater awareness of health—both their own and that of the planet,” Tecklenburg says. “They appear to have a higher level of concern about the environment and for humane treatment of animals.” Vegetarian protein items are also often less costly. Limited-service restaurants are positioned to take advantage of this, in part because young folks are used to eating in that environment.

When by CHLOE opened its first location in New York and people didn’t know much about it, “it was easy for younger diners to understand, but a number of older ones wanted to reserve a table and time slots,” says corporate executive chef Manuel Trevino.

Even though Generation Y and younger consumers continue to grow in influence, the interest in plant-based proteins is extending to their elders.

“People are curious, so there’s more mainstream interest,” says Diana Kelter, foodservice analyst at Mintel. “There is this growing trend toward Meatless Mondays and flexitarian dining that doesn’t see meat as a focus.”

Plant-based protein alternatives have seen a sharp increase, Kelter adds. The use of quinoa in menus, for instance, has grown 62 percent over a three-year period ending March 31.

“I think a big impact has been grain bowls,” she says, noting that they’ve increased 41 percent in the same three-year time period. “They are becoming dominant menu items. They usually include some sort of grain and can include meat, but also a variety of vegetables.”

At the same time, chefs have been more creative in their use of plant-based protein alternatives, especially to make familiar items like burgers or sandwiches. “They are creating these flavors where people don’t feel like they’re missing anything,” she says.

A number of limited-service restaurants increasingly offer non-meat burger options. One of the longest running is Burger King, which uses Garden Veggie Burgers from Kellogg Co.’s MorningStar Farms.

MorningStar Farms has a variety of meatless options and is creating more, says Robert Corscadden, vice president of marketing and innovation for Kellogg’s Specialty Channels. But one thing is paramount. “At the end of the day, it needs to taste good,” he says.

Kellogg’s has come up with a number of tools to help operators point out the effects of choosing a meatless option. One, launched earlier this year, is a Veg Effect Calculator, which shows the impact on the environment of adding meat-free meals.

Corscadden says Kellogg’s also has worked with chefs to find new ways to use MorningStar products. Robert Sikkila, executive chef for Chartwell’s Higher Education Division at DePaul University in Chicago, says this education opened his eyes.

“I knew of the existence of their products, but I never thought of them as more than a patty,” he says. With some creativity, however, he came up with several new dishes, including a stuffed pasta and eggs benedict–like menu item.

One company, Impossible Foods, is manipulating the proteins in plants to create alternatives that imitate the taste, texture, and aroma of burgers and other meats, including juices. Its first product, a burger, is being tested at a New York restaurant.

“The company was truly founded for the love of meat,” says David Lee, chief operating officer. The initial burger product has “a fraction of the environmental footprint but is still cravable for the meat eater.” He expects the burger to do well in a limited-service setting.

Plant-based proteins show up at all types of limited-service restaurants—those that also offer meat, those that seek a meat imitator, and even those not looking to replicate meat at all.

While meat provides more protein than vegetables, grains, and nuts, it’s fairly easy for a typical consumer to get needed protein from these plant-based items, says Ran Nussbacher, founder of Shouk, a vegetarian and Middle Eastern fast casual in Washington, D.C.

“Our society is obsessed with protein consumption, but most of us consume more protein than the body can process,” he says. Combinations of ingredients on Shouk’s plant-based menu easily can provide a diner with more than a third of the daily-recommended protein.

Nothing at Shouk imitates meat. Its top-selling item is roasted cauliflower in a pita or bowl with tomatoes, scallions, tahina, and jalapeño oil. Other pitas or bowls feature chickpeas, mushrooms, black beans, and hummus. The bowls also have rice and lentils.

The guiding philosophy at by CHLOE is to have a vegan menu “that is approachable from every direction for every person,” Trevino says, “but our main goal is to make good food.” Most customers seeking the creative fare are not vegans, he adds.

The small chain, with a half-dozen units in three cities, features a pair of burgers: the Classic version with a tempeh-lentil-chia-walnut patty, and a Guac Burger featuring a black bean, quinoa, and sweet potato patty. The various sauces and toppings for the burgers help replicate the juiciness of a meat burger, the chef says.

By CHLOE’s Whiskey BBQ sandwich uses portabella mushrooms and seitan to provide “a meaty-type quality,” while spiced seitan is employed to create chorizo. Dry-roasted tempeh gets an apricot-sriracha glaze in the Spicy Thai salad.

Veggie Grill employs a variety of plant-based meat alternatives in its vegan menu. They include ingredients that imitate chicken, beef, sausage, and crabmeat, among others.

“We work with a lot of companies to make creative burgers and sandwiches, buffalo wings, and more,” says Steve Heeley, chief executive of Veggie Grill, which has more than two-dozen locations on the West Coast.

Eighty percent of the guests are not vegetarian or vegan but are “veggie-centric or veggie-positive,” he says. “They want vegetables at the center of the plate once or twice or three times a week. Our thing is to be innovative, creative, and break the mold.”

Among the ideas are blackened tempeh and crispy high-quality tofu. The Grilled Quinoa and Veg Burger uses a scratch-made patty of quinoa, kale, and mushrooms, while the Buffalo Bomber sandwich, featuring a fried Gardein-brand chicken-imitation patty in spicy Buffalo sauce, was recently chosen by a Los Angeles magazine as one of the city’s best chicken sandwiches despite having no real chicken in it.

A number of other restaurant operators feature plant-based protein alternatives as well as meat and fish. Sweetgreen’s salads and bowls can have roasted chicken, steelhead trout, herb falafel, hummus, roasted sesame tofu, a warm portabella mix, or hot chickpeas.

“We err on the side of making things delicious,” Stebner says, adding that the company still “builds guardrails around our menu to keep it healthy. You can make things delicious by adding a lot of fat, a lot of sodium, and a lot of sugar.”

To make falafel, the chickpeas are soaked overnight and then combined with raw onions, garlic, olive oil, lemon juice, and seasoning, including nutritional yeast that takes the place of adding sugar, he says.

Tofu, an item some consumers consider squishy and tasteless, needs special care. “We start with the highest-quality tofu and treat it simply using a proprietary seasoning, [then] flavor it with scallion and ginger, put it in the oven, and serve it hot,” Stebner says.

At health-centric Freshii, there are four protein options: chicken, steak, falafel, and tofu, with kale or quinoa as a base for the salads, bowls, wraps, and burritos.

“I am able to eat a high-protein meal with quinoa, beans, nuts, and seeds, and either tofu or falafel,” says Andie Shapira, the in-house nutritionist for the Toronto-based chain that has 300 units worldwide. “But if you are a meat eater, you can also come in and be satisfied.”

While chicken is the most popular protein, the number of diners choosing plant-based options is growing, she says. Marinades are used to provide the tofu with more taste and to give extra flavor and moisture to the falafel.

“Marinating and pairing them with other flavorful ingredients is a way to amp up the taste experience when enjoying these proteins,” Shapira says, adding that serving them with quinoa or brown rice serves to increase the protein.

Beef, chicken, and salmon are large parts of the menu at New York–based Dig Inn, but the chain, known for its focus on local sourcing and sustainability, pays a lot of attention to veggies. “Most of our customers are looking to eat healthy vegetables,” says culinary director Matt Weingarten, adding that most plates are 70 percent veggies.

With that in mind, Dig Inn has created innovative dishes featuring plant-based proteins, such as the grilled organic tofu, which is served gaucho-style with roasted charred red onions, pickled Fresno peppers, and chimichurri.

“It’s a flip on something usually served with steak,” Weingarten says. The firm tofu is brined, marinated with herbs and garlic, and seared to have a golden brown exterior and custard-like texture near the center. “Our research and development team and I believe anything you can do with meat, you can do with vegetables better.”

A wild mushroom and quinoa cake—sort of like a croquette—is made with quinoa and quinoa flakes, dried mushrooms, walnuts, red beets, and other ingredients, then mixed, sent through a grinder, formed into a cake, seared, and topped with house-made beet ketchup to provide the moisture. “It has a wonderful, rich, umami taste,” he says.

Dig Inn continually works on new vegetable-based proteins, which change three times a year, Weingarten says. “The proteins we serve, animal-based or not, are always complementary with the other vegetables on the plate.”