This dates years back i guess Oda got very nervous when somebody asked him about it.
SBS volume 20
D: WHAT HAPPENS IF A PERSON EATS A HITO HITO NO MI?
O: I suppose I should say they "BECOME HUMAN". Uh, I guess you could say that means like becoming an adult, or finding your true spirit or something. So basically, people will live more human-like. Well. I guess you could say that. Or not. Basically, not. Goodbye. (runs away).