C is for the caffeine jolt you give me.

 O your taste and odor are a hit.
 F is how you seem to fight diseases.  (see first reference below)
 F is how you  finally make me shit.    (The hospital seems to always want a stool sample.)    
 E is how I really do enjoy you.
 E you also elevate my mood.  (see second reference below)
 Put them all together they spell COFFEE.
 You are about my favorite food.