  Helicity preserving nanostructures and metasurfaces have been recently
proposed as suitable candidates to enhance spectroscopic features of chiral
matter. With this in mind, we highlight that losses in the constituent
nonmagnetic materials dramatically affect the possibility of constructing
structures which conserve helicity. We first present a general procedure that
permits the evaluation of the normalized helicity expectation value,
$\langle\hat{\Lambda}\rangle$, i.e. the observable that permits the
identification of helicity preserving scatterers. We then apply this procedure
to the case of a chiral sphere, which in an orientation averaged picture can
capture the optical response of chiral inorganic nanostructures, obtaining a
widely applicable analytical expression of $\langle\hat{\Lambda}\rangle$ for
this type of objects. Finally, we numerically show that optical losses impose
an upper bound to the helicity expectation value on nonmagnetic core-shells and
chiral spheres.
