Cats are susceptible to external stressors (eg, environmental changes, forced confinement, unpredictable handling by unfamiliar humans, changes in routine, continued exposure to high-frequency sounds). Studies have shown that cortisol secretion increases when cats are exposed to these events chronically. Ingestible, bioactive peptides (eg, alpha-casozepine, tryptophan) have been reported to have a calming effect on humans. Alpha-casozepine is derived from a major protein in milk, which is believed to cause an anxiolytic effect by binding to gamma amino butyric acid (GABA) receptors. Tryptophan is the precursor for the neurotransmitter serotonin (5-HT) and kynurenine. The anxiolytic effects of dietary tryptophan are likely facilitated by central 5-HT synthesis and signaling.
In this study, 21 healthy, client-owned cats were divided into 2 groups. The control group (n = 11) was fed a balanced commercial diet, and the study group (n = 10) was fed a novel balanced prescription diet that contained alpha-casozepine and tryptophan. Plasma and urine cortisol levels were measured before the study and after 8 weeks. Plasma cortisol levels served as an indicator of acute stress. Urine cortisol levels were used to estimate change change in cortisol over the 8-week study period. There was no significant change in plasma cortisol levels in either group. The cats treated with the study diet had a 40% reduction in urinary cortisol levels after 8 weeks, whereas those in the control group had no significant change in urinary cortisol levels.