β-lactoglobulin Trp peptide, Val-Ala-Gly-Thr-Trp-Tyr, Val-Ala-Gly-Thr-Trp, and Gly-Thr-Trp at two respective doses were examined and found to decrease anxiety-like behaviors, increase Trp concentration (the precursor of 5-HT), and increase the activity of THP (the key rate-limiting enzyme of the serotonin pathway) while enhancing serotonin (5-HT) synthesis and the ratio of 5-HT/Trp, to different extents, in the brain tissue. The gene discussed is HTR5A; the disease is Anxiety.