First broadcast on  

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

There have been many anecdotal reports of the beneficial effect of low protein diets on behaviour in dogs, especially on aggression - but few scientific studies have been performed.

Many authors have suggested that high protein rations may have a role to play in aggressive behaviour in dogs but only a few scientific studies have been performed to demonstrate the benefits of low protein diets.

Why should dietary protein affect aggressive behaviour ?

It is known that some amino acid concentrations in the brain (eg tryptophan) can affect behaviour and cause aggression . Amino acids are the primary chemical units that are linked together to form proteins and many are essential nutrients that must be supplied by the diet. Altering the type and amount of protein intake can increase or decrease specific amino acid availability.

It is known that high ammonia concentrations in the blood can affect the brain and cause aggression. Ammonia is a nitrogen-containing breakdown product following protein metabolism, and its blood concentrations increase in some forms of disease eg liver disease and a vascular abnormality called a portocaval shunt.

What is the scientific evidence so far ?

More work needs to be done , but from the studies published so far it appears that : 

  • Dogs fed a "low" protein ration may show a decrease in territorial aggression behaviour
  • A "low" protein ration may be helpful in managing dogs with dominance aggression 
  • A ration supplemented with the amino acid tryptophan may be helpful in managing dogs with dominance aggression or territorial aggression


DeNapoli J.S et al (2000) Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression and hyperactivity in dogs . Journal of the American Veterinary Medical Association 217: 504-508


Updated October 2013