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Food that affects the mood of dogs

What is fed to animals influences their physical health, but the concept that diet also affects mental health and behaviour is often overlooked. However, nutrition is the fuel for the body and the brain, which is why it has a leading role in animal mental health. We will be analysing how diet and different nutrients impact the behaviour and mood of pets.

Functioning of the brain

Nutrition impacts every cell and metabolic process in the body. Just as a car cannot function without gasoline or gas, the brain and nervous system cannot function without the necessary components. All activities and functions of the body are directed and connected by networks of neurons (nerve cells). If neurons cannot ‘communicate’ with each other in an optimal way, their networks will be affected and consequently their behaviour will suffer as well.

We need to recognise that all behaviour is a direct manifestation of activity in the brain and central nervous system. The behavioural outcome is secondary to the underlying moods, emotions, and motivations. Most studies and research in animals are carried out in order to analyse the presence, prevention or absence of physical diseases, as opposed to mental or behavioural issues.

It is often said that the intestine is the second brain of human beings, but is this statement true if it is transferred to pets? It remains to be seen. A thesis carried out in 2009 for the University of Wageningen focused on analysing and evaluating the impact of feeding on two physiological systems involved in the regulation of canine behaviour.

Dietary fibre and canine behaviour

The potential impact of dietary fibre on satiety and behaviour in dogs was evaluated. To do this, two in vitro fermentation studies were conducted to analyse microbial fermentation activity in the canine gastrointestinal tract from two diets with different fibre fermentability.


  • It was found that the secretion of hormones related to satiety did not differ between the two treatment groups
  • Dogs fed a diet high in fermentable fibre showed less motivation or desire to eat 6 hours after their morning feed ration and, in turn, less activity, compared to dogs fed a diet low in fermentable fibre
  • Dogs in both treatment groups did not differ in their level of response to short-term activities performed between five and seven hours after the morning meal

It was concluded that the type of dietary fibre used in the food can have an impact on canine behaviour in terms of their levels of motivation. However, metabolites related to satiety have not been affected by the type of dietary fibre, indicating that other mechanisms were also involved in the feeling of satiety.

Tryptophan and the mood of animals

The second analysis carried out was about the essential amino acid tryptophan, which is the precursor to the neurotransmitter serotonin in the brain, which is involved in mood, stress, and behaviour.

Tryptophan supplementation has previously been shown to reduce anxiety in rats and increase resilience in stressed pigs.

To translate the study to dogs, tests and analyses were performed on a group of anxious dogs and participating pets consumed foods with different levels of tryptophan for 8 weeks.

It was found that:

  • Intake of food with a higher level of tryptophan increased plasma tryptophan by 37.4% and its proportion with neutral amino acids by 31.2%. However, the data provided by the owners of these dogs do not provide a significant change in the behaviour of dogs that can be attributed to the particular dietary treatment
  • The diet high in tryptophan and low in protein presented improvements in behaviour, especially a reduction towards aggressive behaviour to mark territory and improved behaviour related to fear, attachment, attention and sensitivity to pain

Other studies’ results:

  • It has been shown that behaviour and mood in rats, pigs and humans can be affected by certain nutrients
  • The physical activity of pigs has been influenced by the type of dietary fibre, probably due to satiety after eating. Fermentable fibres were assumed to be able to stimulate several mechanisms involved in the maintenance of satiety, including stimulation of the secretion of satiety-related metabolites in the gastrointestinal tract
  • Enrichment of dog diets with antioxidants and mitochondrial cofactors has been found to reduce the rate of age-related cognitive decline and associated behavioural changes
  • The inclusion of soy-based ingredients in petfood for dogs resulted in the presence of active phytoestrogens that influence anxious behaviour in rats and impair the social behaviour of monkeys
  • Studies that focused on the effects of the experimental decrease in tryptophan availability showed that, as there was a deficit of this amino acid, there was an increase in aggressive behaviour and a decrease in mood.


The known saying ‘we are what we eat’ applies to dogs and all pets in terms of the influence of food over their moods and behaviours. Unfortunately, to date, there is very limited research in the area of ​​how certain specific nutrients affect the brains and behaviour of dogs.

We trust that, as animal mental health becomes better recognised by both the industry and its owners, the studies and analyses already carried out will be deepened in order to offer the best possible food and nutrition.



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