  We present a calculation of the nucleon sigma term on two-flavor QCD
configurations with dynamical overlap fermions. We analyse the lattice data for
the nucleon mass using the baryon chiral perturbation theory. Using partially
quenched data sets, we extract the connected and disconnected contributions to
the nucleon sigma term separately. Chiral symmetry on the lattice simplifies
the determination of the disconnected contribution. We find that the strange
quark content, which determines the neutralino dark matter reaction rate with
nucleon through the Higgs boson exchange, is much smaller than the previous
lattice results.
