GIVEN the massive interest in the area, it’s not hard to find literature on the topic of “food v. behaviour”. The challenge is distinguishing science from anecdote and more so attributing any effects specifically to the dog as many studies reflect on observations of mice and sometimes humans.
To summarise some overarching thoughts:
1. Protein is most often implicated as influencing behaviour and it is often believed that high-protein diets lead to increased aggression or hyperactivity.8 Studies often focus on specific amino acid neurotransmitter and hormone precursors as responsible dietary links. L-tryptophan (a serotonin precursor) is of particular interest in many species and in the dog it is the concentration of this large neutral amino acid relative to others in the same group which seems to have the greatest effect on behaviour.
Many factors affect the uptake and transport of L-tryptophan across the blood-brain barrier including digestibility, albumin-binding and simple carbohydrate intakes.2 The most notable study to date suggests that a resultant lower territorial aggression score occurred in dogs fed a hightryptophan diet when presented in a moderate-protein formula (n=22).4
2. Fats (lipids), particularly within the omega-3 poly-unsaturated fatty acid group, influence the dopaminergic and serotonergic systems of the brain, important to learning, emotions and impulse control.2
Scientific articles relating this theory to canine behaviour are lacking. However, docosahexanoaic acid (DHA) is known to be essential to brain and retinal development in puppies7,10 and one might extrapolate this effect to behaviour in later life.
3. Carbohydrate content and type (physical/chemical properties) determine the postprandial state of the animal, the duration of satiety and relative energy density of the diet in pets. Digestion and absorption of simple monosaccharides affect blood glucose fluctuations (and L-tryptophan availability).2
4. Indigestible carbohydrates (fibre) have been suggested to influence behaviour (particularly foodseeking behaviour) via a number of mechanisms. Fermentable fibres are metabolised by gut microbes to volatile fatty acid (VFA) end-products and with low production adversely affecting colonocyte health, excesses leading to gastrointestinal discomfort with overproduction.
Fibre solubility affects the viscosity of the digesta as well as the propensity for gut-fill, stimulation of intestinal stretch receptors and therefore gastric emptying and intestinal transit time. Indigestible fibre dilutes calories and studies have compared these combined effects to those of wet foods in influencing satiety with variable results.3,5,6 Recent studies more conclusively link high-fibre rations to reduced food-seeking behaviours with clear indications of satiety where a species- and breed-appropriate fibre blend is fed.9
5. Other diet variables relating to palatability, digestibility, energy density, macro- and micro-nutrient profiles will invariably have a role to play in influencing physiology and by nature the systems which influence behaviour. One interesting digestibility concept centres on the holistic consequences of adverse reactions to food.
Within what appears to be a varied spectrum of reactions (from mild intolerance to overt hypersensitivity), diet composition and digestibility may produce a behavioural change: “we can all be a little prickly if we’re not feeling 100%” is a phrase we all sympathise with and ARF/dietary links have been suggested in conditions showing neurological outputs such as canine epileptoid cramping syndrome.1
All considered, it certainly makes sense that diet can influence behaviour in our pets. This may be through method of feeding, quantity of food (sluggishness with weight gain or scavenging when starving) and composition of the diet fed. Faced with a case like Odie it’s wise to consider her specific, individual needs.
With regards to nutritional requirements we often have the choice to select a product appropriate to her age, body condition, neutered status and often even breed. But the decision to move on to another product or return to the original diet needs to be made in consort with her owners.
Regardless of modifications to be made to Odie’s general lifestyle (increased exercise, further training or environmental stimulation) and feeding regime, you’re confident that a diet which suits her and her owners is out there. Perhaps it will be a higher fibre or L-tryptophan supplemented diet she will settle on.
When it comes to your turn to give your input at your staff meeting, you take to the floor with “of course food influences behaviour – our bodies are a reconstituted mix of what we eat after all!”
References
1. Black, V., Garosi, L., Harvey, R. and Gale, J. (2014) Phenotypic characterisation of canine epileptoid cramping syndrome in the Border terrier. Journal of Small Animal Practice 55 (2): 102-107.
2. Bosch, G., Beerda, B., Hendriks, W. H., Ver Der Poel, A. F. B. and Verstegen, M. W. A. (2007) Impact of nutrition on canine behaviour: current status and possible mechanisms. Nutrition Research Reviews 20: 180-194.
3. Butterwick, R. F. and Markwell, P. J. (1997) Effect of amount and type of dietary fiber on food intake in energyrestricted dogs. American Journal of Veterinary Research 58: 272-276.
4. DeNapoli, J. S., Dodman, N. H., Shuster, L., Rand, W. M. and Gross, K. L. (2000) Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression and hyperactivity in dogs. Journal of the American Veterinary Association 217: 504-508.
5. Jewell, D. E. and Toll, P. W. (1996) Effects of fiber on food intakes in dogs. American Journal of Clinical Nutrition 3: 115-118.
6. Jackson, J. R., Laflamme, D. P. and Owens, S. F. (1997) Effects of dietary fiber content on satiety in dogs. American Journal of Clinical Nutrition 4: 130-134.
7. Lauritzen, L., Hansen, H. S., Jorgensen, M. H. and Michaelsen, K. F. (2001) The essentiality of longchain n-3 fatty acids in relation to development and function of the brain and retina. Progress in Lipid Research 40: 1-94.
8. Schroll, S. (2010) Food and behavior – Can food have an influence on behavior? Veterinary Focus 20 (1): 2-6.
9. Weber, M., Bissot, T., Servet, E., Sergheraert, R., Biourge, V. and German, A. J. (2007) A high protein, high fiber diet designed for weight loss improves satiety in dogs. Journal of Veterinary Internal Medicine 21: 1,203- 1,208.
10. Zicker, S. C., Jewell, D. E., Yamka, R. M. and Milgram, N. W. (2012) Evaluation of cognitive learning, memory, psychomotor, immunologic and retinal functions in healthy puppies fed foods fortified with docosahexaenoic acid-rich fish oil from 8 to 52 weeks of age. Journal of the American Veterinary Association 241: 1-12.
Further reading
Bowen, J. (2014) Canine Feeding Behaviour. Veterinary Focus 24 (3): 8-15.
Milgram, B. (2014) Dietary Strategies in Regulation of Behavior and Cognition in Dogs. In: proceedings of the International Working Dog Convention, Royal Canin Elite Breeders Club, La Grande Motte.
Muller, G. (2006) Nutritional management of hepatobiliary and pancreatic diseases. In: Pibot, P., Biourge, V., Elliott, D. (eds), Encyclopaedia of Canine Clinical Nutrition. Paris, Aniwa, pp452-461.
