Taygensmom, when DS went to solids he battled constipation a bit, so from speaking with other Mums and reading, over ripened, yucky brown, ready for the banana bread making bananas are a laxative whilst normal ones are good for binding a la the BRAT diet for diarrhea. Lo and behold it was true, worked for DS and also for me when I am bunged up.
Probably from the breaking down of the natural fruit sugars, it makes the banana have a "corn syrup effect." Which BTW, golden corn syrup is a good for constipation relief but not very good for you or your teeth!
HTH,
Aisling x
A x