OAK BROOK, Ill.— McDonald’s Corp. said Monday it will replace high-fructose corn syrup in its sandwich buns with sugar as part of an effort to simplify its ingredients and satisfy increasingly conscientious customers.

The fast-food giant also is rolling out Chicken McNuggets and some breakfast items free of artificial preservatives and said it has curbed the use of chicken raised with antibiotics that are also commonly used on humans a year earlier than planned.

Mike Andres, president of McDonald’s U.S. operations, said the “sweeping change” will affect 50% of the menu. McDonald’s is in the midst of an attempted turnaround designed to satisfy diners who have asked it to do away with ingredients including high-fructose corn syrup, which some research suggests may cause weight gain and diabetes.

The burger chain also is racing to keep up with rivals who have been quicker to embrace the so-called clean-label movement. Food makers from General Mills Inc. to Yum Brands Inc.’s Taco Bell have begun stripping their products of ingredients that have made many customers wary.

Since taking over as chief executive last year, Steve Easterbrook has pushed McDonald’s to improve its familiar product offerings. McDonald’s last year returned to its original Egg McMuffin recipe, which calls for butter instead of liquid margarine because many consumers didn’t understand exactly what liquid margarine is, the company said.