shelleycat
A bit of the former but msotly the latter, altho the reaction is not occuring in the tummy per se, it's happening inside the liver. Most of what we consider to be tummy pains/weirdness is actually the liver/small intestine! Everything gets to it via the bile ducts etc., and it just goes crazy with all that oil.
Much of the queaziness is the gallbladder contracting due to the juice.