  Observations of stellar CNO isotope ratios indicate the presence of
additional mixing processes on the red giant branch. An estimate of the
resulting stellar He-3 depletion is made, as a function of stellar mass and
metallicity. Based on stellar nucleosynthesis and galactic chemical evolution
calculations, we determine the degree to which the destruction of He-3 due to
such extra mixing processes can influence the inferred primordial abundance of
( D + He-3 ). We find that the extra mixing processes may increase the upper
limit of the inferred primordial ( D + He-3 ) / H ratio by about 20%. The
implications of this for baryonic dark matter bounds, and constraints on the
relativistic degrees of freedom in the early universe, are discussed.
