  Extending our recently published $SU(2)$ results for zero temperature we now
compute the QCD equation of state for finite isospin density within the three
flavor Nambu-Jona-Lasinio model in the mean field approximation, motivated by
the recently obtained Lattice QCD results for both zero and finite
temperatures. Like our previous study, here also we have considered both the
commonly used Traditional cutoff Regularization Scheme and the Medium
Separation Scheme. Our results are compared with recent high-precision lattice
simulations as well as previously obtained results in two-flavor
Nambu-Jona-Lasinio model. The agreement between the lattice results and the
predictions from three-flavor NJL model is very good for low values of $\mu_I$
(for both zero and finite temperatures). For larger values of $\mu_I$, the
agreement between lattice data and the two-flavor NJL predictions is
surprisingly good and better than with the three-flavor predictions.
