  We investigate pion superfluidity in the frame of two flavor
Nambu--Jona-Lasinio model beyond mean field approximation. We calculate the
thermodynamics to the next to leading order in an expansion in the inverse
number of colors, including both quark and meson contributions at finite
temperature and baryon and isospin density. Due to the meson fluctuations, the
Sarma phase which exists at mean field level is washed away, and the
Bose-Einstein condensation region at low isospin density is highly suppressed.
