Mike, i've had this problem only with not-quite ripe
bananas. Very ripe, verging on almost brown ones, do
not affect me this way.

>  I have started to notice that every time I eat a
> banana, I get a feeling
> that is sort of a cross between a hunger pang and a
> stomach ache. It never
> lasts very long, but it is an unmistakable
> after-effect that I feel after I
> eat a banana which I never feel after eating any
> other food.