There are no health consequences per se of the time shifting and that is because the physics have been worked out smoothly to make this not only feasible but in effect a perfect restoration. This allows even a large-scale portion of physical existence to move about through time and then return again without any difficulty or error in the translation. This seems wholly impossible to the rational mind for all of the usual reasons stemming from false teachings to precondition humans to disbelieve and such notions as being truly science-fiction unsupportable by laws of physics. This is simply not true and the proper engagement of the forces of energy in the universe can cause this to happen quite readily. It is no different than other physical forces. The manipulation of time can be quite readily controlled and is highly predictable as well. It is no different than gravity in that regard. One can predict quite accurately the consequences on falling objects of gravitational forces and the interplay of orbital velocity with gravitational influences. It is well worked out science. Time travel is no different and has no ambiguities to the astute scientist who understands the principles. So, for advanced extraterrestrials, this is quite straightforward.