Cage-free chickens in a barn near Hershey, Pa., get to roam and perch on steel rods, but they don't go outside. This week, McDonald's became the latest big buyer to demand cage-free eggs. Dan Charles/NPR hide caption

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Kale is not only loaded with nutrients, but it's become a emblem of a healthy lifestyle that's increasingly appealing to Americans ready to move away from processed, high-calorie food. Peet Sneekes/Flickr hide caption

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An order of McDonald's Chicken McNuggets in Olmsted Falls, Ohio. McDonald's says it plans to start using chicken raised without antibiotics important to human medicine. Mark Duncan/AP hide caption

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A U.S. company that supplies meat to some fast-food chains in China has pulled all of its products, some of which were chicken nuggets sold in Hong Kong, made by a Chinese subsidiary. Kin Cheung/AP hide caption

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McDonald's was the featured sponsor of the annual meeting of the California Dietetic Association in 2014. Alan Broadhead/Flickr hide caption

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Fast-food workers march toward the Smithsonian's National Air and Space Museum in Washington, D.C., on Thursday. Similar rallies occurred in about 100 cities across the U.S. Morgan Walker/NPR hide caption

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