  We perform a thorough computation of the one-loop corrections from both
scalar and tensor degrees of freedom to the power spectrum of curvature
fluctuations for non-canonical Lagrangians in single-field inflation. We
consider models characterized by a small sound speed c_{s}, which produce large
non-Gaussianities. As expected, the corrections turn out to be inversely
proportional to powers of c_{s}; evaluating their amplitudes it is then
possible to derive some theoretical bounds on the sound speed by requesting the
conditions necessary for perturbation theory to hold.
