Landsberg G, Milgram B, et al. Therapeutic effects of an alpha-casozepine and L-tryptophan-supplemented diet on fear and anxiety in the cat. J Feline Med Surg. 2017 Jun;19(6):594-602.

This study was designed to determine the effectiveness of a diet supplemented with L-tryptophan and alpha-casozepine (RC Calm Diet^®). The diet was compared with a control diet to assess its ability to reduce fear and anxiety in cats previously assessed to show fearfulness to people. The authors hypothesized that the RC Calm Diet would reduce anxiety and fear in cats assessed to be fearful of humans compared to a matched group of fearful cats fed a control diet.

The authors sought to examine the effect of the diet on anxiety and fear in the tested subjects. Anxiety responses are those responses occurring in relation to uncertainty and an anticipated threat, whereas fear responses occur in direct response to an actual dangerous situation or stimulus.

The study design was a parallel group design with the control group matched for level of fearfulness. Each group contained 12 study subjects. For the initial 2 weeks of the study, both groups were fed a control diet (Purina Cat Chow), following which a series of three tasks was conducted. The diet of the test group was then changed to RC Calm Diet. The cats were fed this diet for 2 weeks before the tasks were repeated at that time and an additional 2 weeks later.

The tasks set out to assess the subjects’ anxiety and fear to specific situations and stimuli. The first task involved the evaluation of the response to an unfamiliar human in a familiar room (homeroom test: HRT); the second task involved the evaluation of the response to being placed into an unfamiliar room with no human present (Open field test: OFT); and the final task involved evaluation of response to an unfamiliar human in the OFT room (human interaction test: HIT).

In each of the task settings, the authors evaluated a number of behaviors. These included distance traveled, inactivity duration, inactivity frequency and vocalization frequency. The subject behavior in the OFT was thought to best represent an anxiety response, when a cat is in a situation that is unfamiliar, but no specific threat is actively presenting itself.  The behavior response to the presence of unknown humans represented a fear response made in the presence of a specific threat of danger. For the HIT, the researchers made 4 additional observations, including frequency and duration of approach and contact with the unknown human.

The authors found no significant effects of the diet on the HIT, but significant changes in the OFT. The authors concluded that the diet may offer a selective benefit in reducing anxiety but minimal reduction of fear. This is consistent with previous findings in which the anxiolytic diazepam did not change behavior in HIT. A reduction in anxiety may be limited to moderate anxiety-provoking situations only. Vocalization was reduced in the HIT compared to the OFT, possibly due to fear of the unknown human leading to decreased vocalization. As with the diazepam study, cats classified as fearful were found to be more inactive than non-fearful cats. The authors point out some limitations of the study in that cats selected may have been too fearful for the diet to have an impact, or that the study diet was fed for too short a period. In future, a larger number of subjects, possibly those cats classified as minimally fearful or non-fearful in the homeroom could provide more insight.

Due to the presence of both with L-tryptophan and alpha-casozepine in the Royal Canin Calm diet, it is not possible to determine whether reduced anxiety occurred as a result of the L-tryptophan, the alpha-casozepine or both ingredients in combination. (KSD)