  The nuclear polarizability effects in hyperfine splitting of light atomic
systems are not well known. The only system for which they were previously
calculated is the hydrogen atom, where these effects were shown to contribute
about 5\% of the total nuclear correction. One generally expects the
polarizability effects to become more pronounced for composite nuclei. In the
present work we determine the nuclear polarizability correction to the
hyperfine splitting in He$^+$ by comparing the effective Zemach radius deduced
from the experimental hyperfine splitting with the Zemach radius obtained from
the electron scattering. We obtain a surprising result that the nuclear
polarizability of the helion yields just 3\% of the total nuclear correction,
which is smaller than for the proton.
