"We are what we eat." The old nutritionist's maxim applies perfectly to the animal world as well. In a dog's diet, it is indeed possible to find a link to its behaviour. For example, it is easy to come across disorders related to eating behaviour. These include coprophagia (ingestion of one's own or others' faeces), pica (ingestion of inedible or unpalatable items), bulimia and anorexia. To these can be added drinking excessive amounts of water when this is not caused by physiological problems. Coprophagia, for instance, one of the most widespread disorders of this kind, can often be associated with dietary deficiencies or certain conditions of the gastrointestinal tract. In other cases, however, it may be the expression of a behavioural disorder — for example, exaggerated exploratory behaviour, a bid for the owner's attention, a symptom attributable to a state of anxiety, stress or boredom.

Also in this same category is pica — that is, the ingestion of plastic, paper, stones or other inedible objects. It is a problem that frequently occurs in young dogs (dogs, especially as puppies and adolescents, explore with their mouths, biting and chewing the objects they find), but also in elderly animals that are progressively losing touch with the reality around them. Pica too is a source of considerable complications, as many dogs subsequently require surgery because the ingested object has obstructed the stomach or intestine.

"Some forms of eating behaviour disorder may stem from mistakes in the owner's management, while others certainly do not. For example, coprophagia could develop in a puppy as a consequence of punishments inflicted by the owner, in order to 'make the evidence disappear'," explains Dr Elena De Leonardo, a veterinarian specialising in behaviour. "Let us always remember that puppies, like children, take a little time to achieve sphincter control. A puppy that makes a mess should never be punished, nor should an adult dog, because it is 'signalling' that there is a problem. Pica itself is also an eating behaviour disorder that could be due to management errors. During the oral exploration phase, a puppy licks or chews different objects and materials to broaden its knowledge of itself and the outside world. The intervention of an owner who commands it to drop something, or worse still snatches the stolen morsel from its mouth, can stimulate and then, over time, reinforce the animal's possessive and competitive motivation. In this way, the dog will learn to guard and hold on to the object, or to swallow it to avoid losing it." This, in brief, concerns eating disorders that have a behavioural origin. In these cases, it is essential to seek veterinary advice and a check-up, which can resolve the issue or provide fundamental guidance both for the behavioural problem and for any underlying conditions that may be concealed within its manifestation.

When diet determines behaviour

But what links a dog's diet to its behaviour? "It is now well established that the type of diet too," continues Elena De Leonardo, "can influence behaviour. We must, in fact, bear in mind that food introduces nutritional substances such as amino acids, proteins, carbohydrates, minerals, vitamins — or toxic substances and/or preservatives and additives that can have a direct or indirect effect on the production of neurotransmitters and therefore on the central nervous system (CNS). For example, tryptophan, an amino acid, is the main precursor of serotonin (a neurotransmitter of great importance for behaviour in general) and is found primarily in protein-rich foods. However, if the diet does not include the right amount of carbohydrates, the level of tryptophan remains high in the blood but is unable to enter the CNS, and so it will not be converted into serotonin. It is for this reason that I always advise against a high-protein diet without carbohydrates. A deficiency of endogenous serotonin can, in fact, have a negative impact on impulsive behaviour (social inhibition) and aggression, as well as on sleep and sexual behaviour. An excess of flavourings and flavour enhancers such as sodium glutamate can also be highly harmful, because in this case they have an excitatory effect on the central nervous system itself."

The links between behaviour and diet in dogs

Modern nutritional theories on animal feeding favour, as far as possible, a natural diet free from chemical or synthetic components such as additives and/or preservatives. Dr De Leonardo continues: "The chemical substances introduced through nutrients interact in a wide variety of ways with hormones, neurotransmitters and, in general, with all the cells of the organism. Their effect depends on the type of substance used, the quantity and the frequency of administration. These components can cause organic damage, whether acute or chronic, and/or behavioural problems of varying severity, not to mention true 'accumulation' pathologies. And, without necessarily thinking of preservatives or additives, it is enough to know that even a simple food like chocolate contains, for example, chemical substances that are highly toxic for our animals — as does onion…" In short, in the bowl of our four-legged friend lies his wellbeing and his health, but also, potentially, organic or behavioural problems. Having your dog monitored by a veterinary expert, including in the area of nutrition, therefore becomes an obligation for every responsible and attentive owner.