  We report on the first detection of $^{13}$C enhancement in two B[e]
supergiants in the Large Magellanic Cloud. Stellar evolution models predict the
surface abundance in $^{13}$C to strongly increase during main-sequence and
post-main sequence evolution of massive stars. However, direct identification
of chemically processed material on the surface of B[e] supergiants is hampered
by their dense, disk-forming winds, hiding the stars. Recent theoretical
computations predict the detectability of enhanced $^{13}$C via the molecular
emission in $^{13}$CO arising in the circumstellar disks of B[e] supergiants.
To test this potential method and to unambiguously identify a post-main
sequence B[e]SG by its $^{13}$CO emission, we have obtained high-quality
$K$-band spectra of two known B[e] supergiants in the Large Magellanic Cloud,
using the Very Large Telescope's Spectrograph for INtegral Field Observation in
the Near-Infrared (VLT/SINFONI). Both stars clearly show the $^{13}$CO band
emission, whose strength implies a strong enhancement of $^{13}$C, in agreement
with theoretical predictions. This first ever direct confirmation of the
evolved nature of B[e] supergiants thus paves the way to the first
identification of a Galactic B[e] supergiant.
