  Applying the Hellmann-Feynman theorem to a charged pion gas, the quark and
gluon condensates at low isospin density are determined by precise pion
properties. At intermediate density around $ f_\pi^2m_\pi$, from both the
estimation for the dilute pion gas and the calculation with Nambu--Jona-Lasinio
model, the quark condensate is strongly and monotonously suppressed, while the
gluon condensate is enhanced and can be larger than its vacuum value. This
unusual behavior of the gluon condensate is universal for Bose condensed matter
of mesons. Our results can be tested by lattice calculations at finite isospin
density.
