Study summary · Dogs · Behaviour and cognition · 2021
Behavioural signals, but no clear overall anxiety benefit
A small trial found some changes in behaviour during mild stress tests. It did not demonstrate a clear improvement in owners’ overall anxiety ratings or in the cortisol response.
Why this study matters
A dog exploring more, whining less or spending time near a person may be responding to several things. These measures need to be considered alongside everyday behaviour and physiological results.
How the study worked
Participants
39 pet dogs aged 1–6 years: 18 allocated to supplement and 21 to placebo. Dogs that were aggressive or difficult to handle were excluded. Usable cortisol samples varied by visit; the day-30 comparison included 27 dogs.
What happened?
Daily capsules combining fish hydrolysate and a superoxide-dismutase-rich melon concentrate. Four brief tests covered an unfamiliar room, human interaction, noise and a novel object on days 0, 15 and 30.
The comparison
Placebo capsules over the same period.
What was measured?
Twelve recorded behaviours, change in salivary cortisol around testing and owner-reported changes in anxiety.
What the researchers found
| Outcome | Reported result | How to read it |
|---|---|---|
| Owner-reported anxiety | Less anxiety in 5/18 supplemented dogs and 3/20 placebo dogs; overall ratings P=.461 | No statistically significant group difference; one placebo owner response was missing. |
| Cortisol response | No significant treatment effect; day-30 comparison P=.544 | The study did not demonstrate a reduced physiological stress response. |
| Recorded behaviours | Treatment-by-session differences for several behaviours; directions varied across tests | A mixed pattern, not a single consistent reduction in stress. |
| Human proximity, activity and yawning | Some overall treatment comparisons were only trends (P=.098 or P=.07) | Trends should not be presented as established effects. |
What strengthens the evidence?
Random allocation, double blinding, placebo controls and video scoring strengthen the design. The study included pet dogs and checked agreement between behavioural raters.
What limits the conclusions?
The study was small and lasted only one month. Many outcomes and comparisons, some missing samples, repeated exposure to the tests and baseline activity differences complicate interpretation. Directions of behavioural change were mixed. Some reported trends, including P=.098 and P=.07, were not statistically significant. The combination cannot establish a benefit from either ingredient alone.
What the researchers concluded
The authors suggested that the combination might support adaptation to mild stressors and interactions with unfamiliar people.
Evidence.pet interpretation
The most defensible conclusion is that this formulation may alter some responses in this testing setting. That is narrower than showing that it treats an anxiety disorder or improves welfare in daily life. The absence of a clear cortisol or owner-rating benefit should remain visible alongside positive behavioural findings. The trial provides no basis for assuming that ordinary fish, fish oil or any fish-derived ingredient will have the same effect. Persistent fear or distress warrants an individual behavioural assessment, rather than relying on this study as proof of treatment.
Funding and author interests
MP Labo funded the study under contract and provided equipment and cortisol analyses. Titeux, Gilbert and Padilla disclosed their contracted research relationship.
Read the original research
Titeux E, Padilla S, Paragon BM, Gilbert C. Effects of a new dietary supplement on behavioural responses of dogs exposed to mild stressors. Veterinary Medicine and Science. 2021;7(5):1469–1482. doi:10.1002/vms3.560.
Ingredient context: Fish protein hydrolysate. Read how preparations differ and what to look for on a product label.
Evidence.pet editorial summary · Study ID STU-023 · Source checked 23 September 2026. Strengths, limitations and interpretation are our editorial assessment, not a formal evidence grade.
Original Evidence.pet commentary based on full-text appraisal, completed 23 September 2026. No source figures are reproduced. This is not a systematic review or formal certainty grade.