Jan, I have also heard about formula having a soporific effect. Peter
Hartmann talks about the casein being broken down into caseinomorphins,
which have a morphine-like effect. Hence the advertising claim that a
certain casein-dominant formula is good for "hard-to-settle" babies. In the
calf, this is a desirable effect as it allows the mother cow to go off and
graze in peace, while her calf lies quiet and still in the grass - less
likely to be spotted by predators. Something like this I think. Food for
thought, eh?

Joy Anderson IBCLC
Perth, Western Australia