  Effective interactions, when defined in a coarse grained sense, such as Vlowk
at the scale 450 MeV, display a remarkable symmetry pattern. Serber symmetry
works with high accuracy for spin triplet states. Wigner SU(4) spin-isospin
symmetry with nucleons in the fundamental representation works only for even
partial waves exactly as predicted by large Nc limit of QCD with accuracy
O(1/Nc^2). This suggests tailoring the very definition of effective
interactions to provide a best possible fulfillment of long distance
symmetries. With the Vlowk definition Wigner symmetry requires that chiral
potentials have low cut-offs (450 MeV). Perturbative saturation of heavy
mesonic resonances does not faithfully display the Serber symmetry pattern.
