Milk for McDonald's Milk Jug low-fat milk and Milk Jug fat-free chocolate milk will soon be sourced from cows not treated with rBST, it announced last week.
The Milk Jug products are "popular choices" in Happy Meals, it added.
rBST, also known as recombinant bovine growth hormone (rBGH), is a synthetic growth hormone.
Milk from rBST-treated cows contains higher levels of insulin-like growth factor (IGF-1), a growth hormone that has been linked to an increased risk of cancer. But, according to the American Cancer Society (ACS), "evidence for potential harm to humans is inconclusive."
The US Food and Drug Administration (FDA) considers dairy products from rBST-treated cows safe for human consumption. But outcry in the US has led many manufacturers and retailers to market only milk rBST-free milk.
"While no significant difference has been shown between milk derived from rBST-treated and non-rBST-treated cows, we understand this is something that is important to our customers," said Marion Gross, senior vice president of McDonald's North American supply chain.
In the same statement, McDonald's announced plans to only serve chicken treated with antibiotics that "aren't important to human medicine."
“Our customers want food that they feel great about eating – all the way from the farm to the restaurant – and these moves take a step towards better delivering on those expectations,” said Mike Andres, president, McDonalds USA.