The National Park Service is introducing new food standards Wednesday that will eventually require parks across the country to offer healthy food options to their millions of annual visitors.

A bison looks back as it crosses a road in Yellowstone National Park. Bison tenderloin is now on the menu at some of the park’s dining facilities. (Erik Petersen for The Washington Post)

The program, tied to first lady Michelle Obama’s healthy diet initiative, is being unveiled by Interior Secretary Sally Jewell and National Park Service Director Jonathan Jarvis at 11 a.m. at a food kiosk near the Lincoln Memorial.

Chefs from major concessionaires operating at parks around the country will join White House chef Sam Kass in dispensing free samples to passers-by of the new menu items, including bison tenderloin, free-range chicken breast, black bean sliders, sweet potato cakes, berry yogurt parfaits and rain forest coffee.

“Our national parks are renowned around the world for their breath-taking landscapes and important cultural and historical sites,” Jewell said in a statement prepared for the event. “Today, as part of the administration’s efforts to promote healthier lifestyles, we are making sure that great food is always an option for national park visitors.”

“There is no reason that you should have to take a vacation from eating well when you visit a national park,” Jarvis said.

The standards, developed in conjunction with many park service concessionaires, will apply to more than 250 food and beverage operations in national parks which collectively serve some 23 million visitors annually.

The healthy food standards include requirements that fruits and vegetables be offered with all entrees, or offered a la carte as side dishes. Low-fat and low-sodium options are to be available.

Half-servings or other reduced-portion sizes are to be offered when possible. As for drinks, at least 30 percent of those offered should have no added sugar, and low-fat and fat-free milk should be available.

The standards will be integrated into all new concessions contracts and applied on a voluntary basis to existing contracts. Existing contracts will be replaced as they expire with new ones incorporating the standards.

The initiative includes guidelines encouraging concessionaires to use local, sustainable foods, including seafood certified as meeting sustainable standards, meat without hormones and antibiotics, and coffee harvested using worker-friendly standards.