The Constipated Banana

As the parents of a three-year-old boy, my wife and I often find ourselves discussing our son's bowel movements—how big was the last one you changed? How soft was it? And so on. As so happens with busy little boys, our son does not always want to stop what he’s doing long-enough to poop, or maybe that is one of the few things in his life that he can control, and so control it is exactly what he does. Whatever. In short, he becomes constipated, and we end up having endless discussions about what to do about it.
Related to this problem, my wife and I have debated about whether we can feed him bananas (he loves bananas, as do I). My wife believes that they add to or cause his constipation. I say that there is no evidence for this assertion that I’ve been able to find, but of course, I have to yield to my wife’s motherly opinion: She spends far more time with our son than I do, and she has perceived a pattern.
Okay, fair enough. But I find another problem entirely when I go out on the web to search for a definitive answer to the question of whether bananas do in fact cause constipation. Everywhere that I’ve looked so far, I have found lots of claims to the effect that bananas are “binding” and therefore cause constipation. What the heck is “binding” supposed to mean? And then, looking further, I find that some people claim just the opposite, and there is even one website which points out the same problem with which I’m dealing, namely, that nobody making these claims cites any references to supporting medical studies. But then the writer goes on to assert—without citing any references—that green bananas are constipating and ripe bananas will relieve constipation. Jeez. Not only is there no supporting documentation, but this statement begs the question of how green is “green,” and how ripe is “ripe?”
Even one of my favorite evidence-based-medicine publications, the UC Berkeley Wellness Letter glossed over this subject with, "...substances in bananas, especially less ripe ones, may, paradoxically, have both a slight "binding" [ugh...] and slight anti-constipating effect." Bottom line, I guess, is that if your kid wants a banana, give it to him or her. It may help their diarrhea. It may help their constipation. It may make them happy, and you can have one too.
Any registered dieticians out there who want to give this question a whirl?