  For a few observables in O(a) improved lattice QCD, we compute discretization
effects arising from the vacuum polarization of a heavy quark at one-loop
order. In particular, the force between static quarks, the running coupling in
the Schrodinger functional and a related quantity, {\bar \upsilon}, are
considered. Results show that the cutoff effects of a dynamical charm quark are
typically smaller than those present in the pure gauge theory. This
perturbative result is a good indication that dynamical charm quarks are
feasible already now.
