Dr. William Sears in The Baby Book recommends
against soy formula as a first choice for many reasons including that «30 - 50 percent of infants who are allergic to cow's milk protein are also allergic to soy protein,» and that «giving an infant soy at a young age,
when intestines are more permeable to allergens, may predispose the child to soy
allergies later on, even as an adult.»