Have you ever gotten diarrhea from eating the spongy stuff?
I consumed my share of coconut meat/milk in Panama when travelling in the interior. Never tried "U", the locals didn't (appear to) eat it. Yes - the milk will give people not accustomed to it diarrhea. (Saw a fair amount of it among Gringos overindulging their first time.) Use it sparingly in a survival sutuation until your body gets adjusted to it.