Summarized from an article in the February 1996 issue of the Journal of the American Veterinary Association (JAVMA)

In this study, four groups of dogs were fed diets containing three different protein levels and the behavior over time recorded by the dogs' owners and the supervising veterinarians. Only one subgroup was reported to show any effect of changes in protein intake; in the rest, no differences in behavior were noted.

The dogs were each classed into one of four behavior groups: those who showed Dominance aggression, those who showed Territorial aggression, those considered to be Hyperactive, and those whose owners reported no behavioral problems. Each group was fed a low (17%), medium (25%) and high (32%) protein diet for a two week period and owners were instructed to score their dogs' behavior on a daily basis.

All dogs in the study were neutered adults, in good health as determined by examination and blood tests. Owners were instructed not to do any behavior modification (training) during the testing period. Each dog's behavioral diagnosis was confirmed by an interview between the dog's owner and a veterinary behaviorist. All dogs in the aggressive groups displayed a minimum of 2 episodes per week in the three months prior to the study. The hyperactive dogs were referred by their own veterinarians.

During the first two weeks of the study, all the dogs were fed their regular diets and their behavior scored by their owners. Areas scored were territorial aggression (aggressive toward strangers at home), dominance aggression (aggression toward owners), excitability, and fearfulness. Then each group was fed each of the test diets for two-week periods and their behavior scored during that time. Caloric intake was kept uniform by keeping the amount of carbohydrate stable and adjusting the fat content to compensate for the differing protein levels.

Within the Territorially aggressive group, two subgroups were identified: those who had pronounced dominant tendencies and those who had pronounced fearful tendencies. While the scores for fearfulness did not vary for any of the dogs in any of the groups during the tests, the scores for Territorial aggression changed significantly for the Territorially aggressive/Fearful group when fed the low and medium protein diets. For the rest of the groups, behavior did not vary significantly with the changes in diets.

The study concluded that a reduction in dietary protein is not generally useful in the treatment of behavior problems, with the possible exception of those with territorial aggression that is the result of fear.

Original article co-authored by: Nicholas H. Dodman, BVMS; Ilana Reisner, DVM; Louis Shuster, PhD; William Rand, Ph.D; U. Andrew Luescher, DVM; Ian Robinson, PhD; Katherine A Houpt, VMD, PhD.