How many low-mass stars do destroy 3 He?

We recall the current status of the long-standing 3 He problem, and its possible connection with chemical anomalies on the red giant branch. In this context, we collect in the liter- ature all the available observations of the carbon isotopic ratio in field and cluster giant stars. Using the HIPPARCOS paral- laxes, we get constraints on the evolutionary status of the field stars of the sample. This allows us to identify the stars that have passed the luminosity function bump and present 12 C/ 13 C ratios in disagreement with the standard predictions of stellar evolu- tionary models. We determine statistically what fraction of low mass stars experience an extra-mixing process on the red giant branch, and are then expected to destroy their 3 He at this evo- lutionary phase. The high number we get satisfies the galactic requirements for the evolution of the 3 He abundance.