If you've reached the end of your leash with your dog's aggressive behavior, talk to your vet about a change in your dog's diet. Various scientific studies have yielded persuasive evidence of a correlation between canine aggression and diet. Not all of them arrive at the same conclusions, and experts on all sides of the issue agree that more research is needed, but these studies report that diet has helped to correct some stubborn aggression problems in dogs.
Tufts Studies on Diet and Aggression
Two studies regarding the effects of diet on canine aggression were conducted by Tufts University Veterinary School and published in the "Journal of the American Veterinary Medical Association." The first study, published in 1996, experimented with levels of dietary protein: low at 17 percent, medium at 25 percent and high at 32 percent. Researchers found that a reduction in dietary protein resulted in significant improvement in dogs displaying fear-based territorial aggression. The second study, published in 2000, also examined the influence of dietary protein on dominance aggression with diets containing 18 percent or 30 percent protein. This time, the researchers concluded that low-protein diets had a positive effect in reducing both types of aggression.
South African Study
A 1997 study suggests that modifying protein content in a dog's diet to control aggression might be substantially less significant than customizing the diet according to the dog's nutritional needs and preferences. The research, published in “Proceedings of the International Conference on Veterinary Behavioural Medicine," studied 100 dogs of various sizes and breeds with a range of behavior problems over five years. Most dogs favored greater quantities of fresh meat products than they were eating previously. Ninety-eight percent of dog owners reported dramatic improvement in aggression and other problem behaviors. The authors concluded that when dogs don't get adequate amounts of food appropriate to their needs, physical hunger motivates behavior problems. They explain that an adequate canine diet is an “unequivocally therapeutic” way of reducing aggression and other antisocial behavior in dogs.
Dietary Carbs vs Protein
Veterinarian Georgina Marquez of the Animal Medical Center of Southern California agrees that some forms of canine aggression are “probably triggered by environmental factors such as the availability and quality of food,” and diet might prove to be an important missing link in this poorly understood area of veterinary medicine. Citing the Tufts' studies, Marquez notes that the theory behind the association linking low-protein diets and aggression is that too much protein inhibits the body's ability to produce the amino acid tryptophan, which the brain needs to manufacture the calming neurotransmitter serotonin. However, Marquez isn't comfortable with the idea of allowing protein levels to drop too low in a canine's diet. As carnivores, they require plenty of high-quality animal protein to keep their blood glucose levels stable. Dogs can't thrive on diets consisting of more than 35 percent carbohydrates, she says, recommending a diet rich in animal proteins, fat and omega 3 fatty acids to keep dogs mellow.
Supplementing Diets With Tryptophan
In a second study, Tufts researchers concluded that supplementing canine diets with tryptophan holds promise for treating both territorial and dominance aggression. Low-protein diets aren't recommended for all dogs, they warn, but even among dogs fed high-protein diets in their study, tryptophan supplementation was associated with significant improvements in aggressive behavior.