In the present study, the anti-stress effects of yeast hydrolysate (YH) were investigated. The YH consisted of crude carbohydrate (23.6%) and crude protein (68.3%) with low contents of crude ash (3.1%) and crude fat (0.3%). Also, acidic amino acids (glutamic acid + aspartic acid) were present in large quantities (14.2 and 5.0 mol%, respectively). Pronase digestion had little effect on the affinity of the YH on 5-hydroxytryptamine (serotonin) and norepinephrine transporters, whereas NaIO(4) oxidation of the hydrolysate decreased the affinity by about 10% at 1,000 microg/mL, indicating that the periodate-labile carbohydrate moiety played a leading role in the affinity effects of the carbohydrate in YH. As a result of brain mapping after the administration of the YH for 3 days in human subjects, a symmetrical distribution of theta and alpha waves in the central and parietal lobes was observed. This brain mapping pattern of theta and alpha wave distribution appears in a psychologically stable state. The YH groups showed improvements in Beck Depression Inventory and Beck Anxiety Inventory scores after YH administration for 2 weeks. Treatment also seemed to have a more significant (P < .05) impact on the somatic manifestations of anxiety as indexed by the Beck Anxiety Inventory scores. Food materials used as a source of YH have been found to be associated with increases in alertness and adaptation to stress.