Apple, cranberry, cran-apple, grape, and pineapple juices have more than grapefruit, orange, or tomato juices.
a. amino acid
b. sugar
c. protein
d. calories

when you rub, you also apply pressure, that pressure can urge the poop to come out. i think that when your rubbing, you also might be slightly breaking it up and that can further fill the stomach.  

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