This article is from the Solid Food for Infants FAQ, by David M. Poduska poduska@cis.ohio-state.edu with numerous contributions by others.
Where does formula fit into this? Generally, the more processed a
formula, the less allergenic the milk proteins in it are. Fresh milk
is more allergenic than exaporated milk, which is more allergenic than
regular formula, which is more allergenic than hydrolyzed formulas;
the latter should be no problem at all, as the proteins are completely
digested into amino acids. They also cost a lot more and probably
taste a whole lot worse. Breastmilk is safer than formula, but if you
have a reason to use formula, it's no doubt worth this small risk.
Women with type I diabetes in their families may decide to breastfeed
longer than they would have otherwise. In the absence of a high risk
for diabetes, it is probably best to go for a cheaper formula unless
the child has already shown problems with allergies. Soy-based
formulas are not associated with diabetes, since their proteins are
quite different (although as far as allergies are concerned, children
who are dairy-allergic are often allergic to soy as well); families
with type I diabetic relatives might prefer soy-based formulas for this
reason.
 
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