All four of my children had severe diarrhea from the tiniest bit of
gluten in the diet for around the first 2 years of life.  My last (a 34
weeker) had severe diarrhea every time I ate anything containing gluten
during the 15 months I breastfed him.  I had  to cut out any grain
containing gluten including not only wheat, but also oats, rye, and
barley.  Corn and rice are not a problem.  (Gluten is what makes bread
stick together, so anything you bake from a gluten-free flour tends to
fall apart.)  I'm not sure about the gluten contents of grains that are
less commonly used in our area.

I think celiac disease causes diarrhea only--never heard of it causing
constipation.

Bonnie Jones, RN, ICCE, IBCLC
from the sunny S.W. USA