  We consider an effective field theory for a gauge singlet Dirac dark matter
(DM) particle interacting with the Standard Model (SM) fields via effective
operators suppressed by the scale $\Lambda \gtrsim 1$ TeV. We perform a
systematic analysis of the leading loop contributions to spin-independent (SI)
DM--nucleon scattering using renormalization group evolution between $\Lambda$
and the low-energy scale probed by direct detection experiments. We find that
electroweak interactions induce operator mixings such that operators that are
naively velocity-suppressed and spin-dependent can actually contribute to SI
scattering. This allows us to put novel constraints on Wilson coefficients that
were so far poorly bounded by direct detection. Constraints from current
searches are comparable to LHC bounds, and will significantly improve in the
near future. Interestingly, the loop contribution we find is maximally isospin
violating even if the underlying theory is isospin conserving.
