Lessons From Soldiers, Felons and Monkeys: Dietary Protein and Behavior Problems in Dogs ::
A lot of mythology surrounds how we feed our dogs. For example, many clients proudly tell me in their initial behavioral consultation that their dogs eat NO “people food.” Of course, they’re quite astonished when I tell them “people food” is precisely what their dogs should be eating! Another myth is that the higher the protein, the better the dog food. High protein somehow equates with quality of the product. In my experience, I’ve found high protein to equate with the quality of behavior problems. Dogs turn protein into energy and a variety of molecules that can cause a range of conditions from aggression to anxiety.
Every living thing depends upon protein molecules. Protein makes up our various body tissues. It builds, enzymes, hormones, hemoglobin, antibodies, and neurotransmitters, the molecules responsible for emotional states. Every natural system, however, requires balance, and a body has a certain requirement for protein, beyond which that balance is upset. In dogs, as in humans, high levels of dietary protein can unbalance emotional states, resulting in behaviors that can become problems.
Protein molecules are made up of amino acids. Tryptophan is one of the essential amino acids found in proteins. It is one of the raw materials for the neurotransmitter serotonin, which controls sleep cycles and helps inhibit anger and aggression. Thus, tryptophan can help relieve anxiety and tension. Protein-rich diets have been shown to diminish levels of tryptophan in the brain.
The canine ancestral diet actually had fairly low, but in ideal conditions, adequate levels of protein. Protein levels depended on which species of animal was being consumed. Wild rabbit, for example contained 16.5% protein, while wild venison contained 21% protein. On average, animal sources contain about 20% protein, the level found in many maintenance dog food formulas. But some maintenance formulas contain 25% protein or more, as do some puppy formulas. So-called “high-performance” formulas may contain crude protein levels of 30% or more. And canned dog food may be 40% crude protein or higher!
Some interesting conventional wisdom comes down through the ages from the Greek and Roman armies. Soldiers were instructed to eat more meat, because that would make them more ferocious in battle and better soldiers. Of course, the meat they were eating was cooked, decreasing the water content and increasing the level of protein, not unlike a “high performance” formula dog food. A study done in a British prison in the 1950’s found that the most violent criminals were eating high-protein diets, contrasted with the lower protein diets of the less violent inmates. Vervet monkeys fed diets low in tryptophan exhibited increased aggression and higher levels of motor activity in general.
How does a low protein diet work to ultimately result in changed emotional states and behaviors? What makes a high protein diet create the conditions for aggressive, anxious or fearful emotional states? The brain depends on food for its tryptophan supply. Tryptophan molecules reach the sites of serotonin synthesis in the brain by passing from the blood through transport channels in the blood-brain barrier, sort of like taking a skywalk from one building to another. While it might seem logical that increasing the amount of protein in the diet would increase the amount of tryptophan in the blood for the brain to use, the reverse is actually true, according to research done at Massachusetts Institute of Technology. Another remarkable finding was that high carb diets caused the amount of tryptophan available for serotonin synthesis to increase, even if the total diet contained only moderate amounts of tryptophan. Further investigation revealed that the tryptophan component of a complete protein represents only about 1-2% of the total amino acids in that protein. Because there are a limited number of “skywalks” from the “blood building” into the “brain building” (transport channels through the blood-brain barrier), the other more numerous and larger amino acids in a high-protein diet out-compete the tryptophan for access. As a result, tryptophan is blocked from the skywalk, levels of tryptophan in the brain fall off, serotonin levels drop, and states such as anxiety may occur or increase. Researchers also found that because diets composed of a high carbohydrate to protein ratio (about 5 or 6 to 1) caused the pancreas to secrete the hormone insulin, which increases the concentration of tryptophan in the plasma compared to other amino acids. Like a policeman directing traffic in the blood, insulin diverts amino acids other than tryptophan into repair of muscle tissue. But because of tryptophan’s unique molecular structure, the insulin policeman green lights it to stay in the blood. So when tryptophan reaches the skywalks, it has many fewer other amino acids to compete with for transport. Levels of tryptophan in the brain then rise, increase the brain’s production of serotonin, and decrease irritability, anxiety and other negative emotional states.
If this optimal movement of tryptophan through the transport channels is to occur, dietary protein levels must be kept at 18% or lower, AND carbohydrate must be 22% or higher. While the MIT research was not done on dogs, a study at Tufts University School of Veterinary Medicine would seem to indicate similar percentages would work for dogs.
That’s some of the research. What actually happens in the real world? My experiences with numerous dogs would seem to indicate that a low protein/high carbohydrate diet has a calming effect. In puppy classes particularly, where clients complain about the excessively mouthy, jumpy boisterous behaviors that are frustrating them, my recommendation to change their pups’ diets from a puppy formula to an adult maintenance formula often generates comments of how much calmer their pups have become, and how it seems easier for the pups to concentrate on learning. In an 8-week class, if the change in diet is started early enough, we do indeed have the chance to see the results. I often smile to hear owners who have elected not to change their boisterous pups’ diets being counseled by those who have done so and seen good results!
Can all those soldiers and felons and monkeys be wrong? Pass the rice and macaroni, please!
References
DeNapoli, J.S. Dodman, N.H., Shuster, L., et.al. Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression and hyperactivity in dogs. JAVMA, 2000;4:504-508.
Dodman, N.H., Shuster, L. Psychopharmacology of Animal Behavior Disorders. Marsden: Blackwell Science. 1998.
Eaton, S.D., Shostak, M., Konner, M. The Paleolithic Prescription. New York: Harper & Rowe. 1988.
Lindsay, S.R. Handbook of Applied Dog Behavior & Training, Vol. I: Adaptation and Learning. Ames: Iowa State University Press. 2000.
Categories: Physical Animal Health, Species Behavior, General Information —
