GSTM1 and anemia (phenotype): The hemoglobin concentrations [Hb] of high-altitude residents increases with altitude.1,2 Approximately 5% of the world’s population lives at altitudes above 1500 m,3 and thus is at risk to suffer from anemia because highland residents rely on adequate iron and vitamin intake4 to foster erythropoiesis for maintaining this chronically elevated [Hb].