This might seem like a funny question, but it actually is not.
My 13 month old daughter started to have constipation and we were trying to figure out what it could have been.
While researching, I found out that you need to stay away from BRAT (Bananas, Rice, Apples, Toast)...the combo that helps you when you have diarrhea. Those four things are actually her favorite. We started to reduce the amount of bananas (she really loved 'nanas') and the others, too and that seemed to do the trick. Upon further research supposedly ripe bananas do not cause constipation.
So my question is...how ripe does a banana have to be so as to not contribute to constipation?
http://www.raw-food-health.net/Bananas-Constipation.html - here's a good reference that talks about ripeness and effects on constipation.