A milk which is free of .beta.-casein A.sup.1 protein in the prevention or treatment of coronary heart disease is disclosed. In addition, a process for the testing of DNA from cells obtained from lactating bovines for the presence of DNA encoding certain .beta.-casein proteins, selecting the bovines on the basis of the testing, and then milking those bovines to produce milk free of .beta.-casein A.sup.1 for use in the prevention or treatment of coronary heart disease is disclosed.