  We employ leading order covariant chiral perturbation theory to compute the
nucleon-pion-state contribution to the 3-point correlation functions one
typically measures in lattice QCD to extract the isovector nucleon charges
$g_A,g_T$ and $g_S$. We estimate the impact of the nucleon-pion-state
contribution on both the plateau and the summation method for lattice
simulations with physical pion masses. The nucleon-pion-state contribution
results in an overestimation of all charges with both methods. The
overestimation is roughly equal for the axial and the tensor charge, and about
fifty percent larger for the scalar charge.
