McDonald’s is taking artificial preservatives out of its most popular menu item, Chicken McNuggets, and from some breakfast items, including pork sausage patties, omelet-style eggs and scrambled eggs. The fast food chain also is removing high-fructose corn syrup from its buns and using real butter on its Egg McMuffins. Coupled with McDonald’s decision in 2015 to buy only chicken raised without antibiotics used to treat humans, these ingredients changes will affect almost half the McDonald’s menu. The company said last year that all its chicken would be free of antibiotics by 2017, but this week announced it had already met that goal.

Consumers have been telling McDonald’s they don’t like artificial preservatives and high-fructose corn syrup, said Mike Andres, president of McDonald’s U.S.A. “Why take a position to defend them if consumers are saying they don’t want them?” Andres said.

The company’s effort to replace liquid margarine with real butter in the Egg McMuffin took six months. The butter has to be softened, then blended to maintain its flavor and consistency. Care must be taken so that the butter is not melted.

McDonald’s already has eliminated artificial preservatives from Chicken McNuggets. Removing preservatives from Chicken McNuggets only required taking the preservative out of the oil in which the McNuggets are cooked. High-fructose corn syrup will be gone from McDonald’s buns this month.

Food analysts say McDonald’s is trying to appeal to health-conscious consumers who like to know what’s in their food and where it came from. The company is working to revamp its image as more modern premium fast-casual while still winning on value.

Analysts say fast food chains use artificial components because those ingredients are cheap. While analysts expect the switch to more natural ingredients to drive up production costs, McDonald’s said it won’t be hiking the price of its food.

Company representatives expressed confidence that the higher cost of many of its new ingredients will not force McDonald’s to raise prices. McDonald’s is determined to hold its prices steady, despite adding premium ingredients such as cage-free eggs and antibiotic-free chicken. Offsetting those higher prices would be this year’s drop in ingredients such as beef and chicken, representatives said.

Making rapid changes company-wide is difficult because of the large volume of ingredients McDonald’s uses, so the company is turning to regional markets to test new ingredients and products. Latino-inspired breakfast bowls, such as an egg white scramble with sautéed baby spinach and kale, are undergoing testing in Southern California. The company is also testing a scrambled egg with cheese and chicken chorizo garnished with McDonald’s hash browns.

Some analysts are casting doubt on the nutritional improvement that will come from McDonald’s changes. “It’s more about perception about the actual healthfulness of the product rather than its nutrition value,” said Stephen Dutton, who analyzes the food industry at Euromonitor International. Michael Jacobson, executive director for the Center for Science in the Public Interest, told the Associated Press that these swaps don’t reduce the food’s calorie count.