 Retail giant Wal-Mart Stores Inc. has announced that all the store-brand milk sold in both Wal-Mart and Sam's Club stores in the United States will now be produced by cows not treated with artificial growth hormones. Approximately 18 percent of dairy cows in the United States are injected with Monsanto Co.'s recombinant bovine somatotrpoin (rBST), also known as recombinant bovine growth hormone (rBGH). An artificial version of the naturally occurring bovine growth hormone, rBST forces cows' bodies to produce 15 percent more milk than usual. Although most cows are not treated with rBST, the milk from many different cows and dairies is often mixed together before being packaged. This means that unless otherwise labeled, most milk sold in the United States probably includes some from rBST-treated cows. Wal-Mart said that its decision came in response to rising consumer demand for hormone-free milk. 'We've listened to customers and are pleased that our suppliers are helping us offer Great Value milk from cows that are not treated with rBST,' said Wal-Mart general merchandise manager Pam Kohn. Wal-Mart is the largest grocery retailer in the United States, with more than 4,000 stores, and the country's largest retail seller of organic milk. The company's move was greeted as a victory by consumer advocates who have campaigned to make hormone-free milk more widely available. While Wal-Mart's action is not expected to produce any drastic or immediate impact on the dairy industry, it demonstrates that the demand for healthy food has reached the mainstream, they said. 'It's reached the tipping point,' said Ronnie Cummins, director of the Organic Consumers Association. 'I think things are accelerating now and people are getting more health conscious and are getting more conscious about the connection between their personal health and the health of the environment.' RBST has been criticized for damaging the health of cows, increasing the animals' suffering and leading farmers to use more antibiotics. Concerns have also been growing about the health impacts of drinking milk from rBST-treated cows. 'When you look at all the surveys of consumer attitudes about food safety, hormones consistently rank way up there, along with pesticides,' Cummins said. Studies have found that cows injected with rBST produce milk with abnormally high levels of insulin growth factor 1 (IGF-1), which has been linked to higher risks of breast, colorectal and prostate cancer in humans. In animal studies, high IGF-1 levels have been connected with an increased risk of diabetes and early death. In part due to health concerns, the use of rBST is banned in Australia, Canada, Europe and Japan. In the United States, rBST has been approved for use since 1993. U.S. Department of Agriculture standards, however, prohibit the use of the hormone to produce milk labeled as 'organic.' Because the high cost of organic milk keeps it out of the price range of many consumers, a new niche within the milk market has developed: milk that is not certified organic, but is guaranteed as not produced from rBST-treated cows . According to Cummins, this milk appeals to health-conscious consumers who don't want to pay for certified organic milk. In response to this growing trend, Safeway Inc. now guarantees that its store-brand milk does not come from cows treated with artificial growth hormones. Going even farther, Kroger Co. does not sell any milk in its 2,500 stores, which includes non-store brands, unless it comes from cows that have not been treated with rBST. Likewise, Starbucks Coffee stores use only hormone-free milk. And it's not just hormone-free milk that consumers are clamoring for; in an attempt to boost flagging sales, Wal-Mart has put great effort in recent years into expanding its selection of 'eco-friendly' or 'healthy' food and clothing. In 2007, it even named an executive in charge of developing more 'green' products. Although Wal-Mart has decided to provide milk from cows not treated with hormones, the company is still undecided on whether to advertise that fact on milk carton labels. Such labels are allowed by the FDA, but have been repeatedly challenged by rBST manufacturer Monsanto. The state legislatures of Missouri, Ohio and Utah are currently considering bills to outlaw rBST-free labels. The state of Pennsylvania actually passed such a law, but it was overturned by the governor. On the federal level, the FDA has already rejected attempts by Monsanto to outlaw the hormone-free labels. Until Wal-Mart decides whether to label its milk, company spokesperson Deisha Galberth said, consumers will just have to find out about the decision from news stories, or from the company's blog or consumer hotline. 