Most people are aware that there’s a link between their brains and their digestive system. When we feel nervous, we say that we have “butterflies in our stomach” to describe the sensation. Before stressful events, people may need to visit the bathroom more often. And on certain occasions, we are aware that our moods can be affected by what we eat, whether it’s when we eat too much and feel grumpy with overfullness, or when we have not eaten enough and we feel “hangry”. And sometimes we also feel a mood change after eating an excess of a particular foodstuff.
Recent research is showing that dogs are no different to us in this regard. Dog moods – and the resulting behaviour – can have a direct link to the type, quantity and frequency of food being eaten.
The science in this area is now reaching a new, detailed level of analysis, with recent studies being particularly pertinent at a time when there has been a surge in the levels of anxious behaviour shown by dogs during the COVID pandemic.
The impact of the digestive tract on behaviour is not just caused by the type of food being eaten, although there is a general principle that a good quality diet with high nutritious value does bring many benefits to pets, both physical and mental. The new understanding of the impact of food on dogs includes a novel area: the microbiome, or the microorganisms, including bacteria, in the bowel.
Pet care company, Purina, has been leading research and awareness in this area.
Readers may already have heard about the human gut microbiome. Studies have shown links between different human gut bacteria populations and certain mental health issues such as depression.
Now scientists are discovering similar links in dogs, with evidence that the gut environment, and the bacteria that are found there, have an effect on brain function and, and consequently, dog behaviour.
Taking this further, a recent study by Purina discovered that the feeding of a specific healthy bacteria, in the form of a probiotic, helped to reduce signs of anxiety in dogs. It’s still early days, but the hope is that in the future, it may be possible to positively influence the bacterial population in a dog’s digestive system to ensure that they have the optimal bacteria to help them feel calmer and more relaxed, rather than anxious and tense.
Special dog “probiotics” have been on the market for some years now: they have been mostly derived from similar human products. The idea is that if a dog is fed capsules or powder containing “good bacteria”, these will seed the digestive system with a fresh population of beneficial bugs.
To date, probiotics have only been used in limited, specific situations that do not include behaviour. Examples include dogs that have been on long courses of antibiotics, or animals suffering from chronic digestive disorders. When these animals are fed specific “good” bacteria, there’s evidence of benefits, primarily in the digestive system.
There are two new ways that science now understands this topic.
First, we are learning more about the specific bacteria which are optimal for dogs. It’s not enough to presume that good “human” bacteria are also good for dogs. Researchers are now finding the precise canine versions that are optimal for particular situations. Some seem to be more helpful with digestive disorders, others have more of a calming effect, and some may have no discernible effect at all.
As an example, in a carefully designed study, Purina scientists discovered that dogs supplemented with Bifidobacterium longum (B. longum) showed significant reductions in displaying anxious behaviours, when compared with dogs fed a placebo. The supplemented dogs also had lower heart rates and salivary cortisol levels (showing that they were suffering from less stress).
There’s a long list of other bacteria which might have similar types of beneficial effects. The job of scientists now is to find out more about which bacteria help, how many are needed, and how they should be given. And then, what type of diet is then needed to maintain this new population of bacteria?
Second, scientists are reconsidering the ways in which an altered gut microbiome can benefit a dog. The old idea was to aim for a simple improvement in digestive health. The new idea is that anxiety can be reduced, and that behaviour can then be improved. But we need to go on from there, to think about what other benefits are possible. Could there be other impacts on dog behaviour, such as specific aims like reduced barking or less aggression? These improvements are likely to be seen anyway when a dog is less anxious, but it’s interesting to speculate if the impact of different gut bacteria could have variable specific impacts.
Ultimately, could the beneficial bacteria be added directly to a pet’s diet as part of the product, rather than being given as a nutritional supplement? Some pet food already has probiotics added, but we need more evidence to see if this really does have any advantage.
These are all questions that are being asked: perhaps, in 2022, we will get closer to having answers.