I like that I can pick either of two reasons why your original body is alive and well, even though it has the mind of a sandwich:
(a) D&D has no concept of "subconscious vital bodily processes", so there are no rules that say whether they stop happening or whether they were even really happening in the first place.
(b) If it _does_ exist, when you _True Mind Switch_, the part in charge of those processes should absolutely remain in its body and not come along for the ride. Otherwise, if a Fey switches minds with a Giant, they will both assuredly die very quickly due to cardiovascular damage.