  We extend the effective field theory approach which successfully describes
ordinary nuclei and nuclear matter to incorporate strangeness in nuclear
structure. Central object is a chiral effective Lagrangian involving the baryon
octet, the Goldstone boson octet, the vector meson octet and a light scalar
singlet. According to the rules of effective field theory, we include all
interaction terms (up to a given order of truncation) that are consistent with
the underlying symmetries of QCD. We develop a mean-field approximation and
study nuclear matter as a simple model for multi-strange systems. A D-type
Yukawa coupling between baryons and vector mesons leads to lambda-sigma^0
flavor mixing in the nuclear medium. We study flavor oscillations in the
nuclear matter ground state which are closely related to the phenomenon of
neutrino oscillations.
