‘When we are considering how a dog is behaving, we really should be considering what is inside the stomach’.1 - Mugford, 1987


While most of us can clearly recognise the connection between diet and poor physical health, when a dog’s behaviour is not what we want, diet is seldom considered to be a possible contributing factor. However, there is increasing evidence to show that what you feed your dog can, and does, influence not only their quality of life as they age, but also how they behave, due to the profound impact that certain nutrients have on maintaining normal physiological and biochemical functioning within the body.

Given the breadth of this topic, the focus of this article will be to briefly highlight the specific role of phytonutrients in our dog’s diets, using a few key examples that most of us have likely experienced with our own dogs.


Key actions and benefits of phytonutrients

Phytonutrients, or phytochemicals, are natural compounds found exclusively in plants – they are what give fruits and vegetables their vibrant color.

In recent years, there has been an explosion in research highlighting the potential role of dietary phytonutrients in the promotion of health and in the prevention of chronic diseases; and while phytonutrients are not essential to keep your dog alive like fats, proteins, vitamins and minerals, it is widely accepted that the consumption of such natural compounds confers protection against oxidative stress, inflammation, vascular dysfunction and metabolic dysregulation, thus reducing several risk factors for a range of different pathological states including obesity, diabetes, cardiovascular and neurological diseases and certain types of cancer.2

Phytonutrients also enhance immunity and intercellular communication, repair DNA damage from exposure to toxins, detoxify carcinogens, balance hormone metabolism, and provide increased benefits to mood, cognitive function and performance.3,4


Aging dogs: how diet can help improve their memory and cognitive function

The brain is extremely vulnerable to oxidative damage, causing death of neurons and resulting in reduced cognitive function and changes in behaviour.5 Senior and geriatric dogs often display canine cognitive dysfunction with impaired learning and memory, increased anxiety, disorientation, a reduced ability to interact socially, house soiling, destructive behaviours, lethargy and disturbances in sleep patterns.6

Feeding senior dogs a diet rich in antioxidants from a mixture of fruits and vegetables along with certain mitochondrial cofactors, has been shown to counteract the effects of free radical damage on the brain, leading to decreased rates of cognitive decline as they aged and improved age-related behavioural changes.7

Brain-derived neurotrophic factor (BDNF) is a key molecule involved in plastic changes related to learning and memory, and acts to protect neurons against death.8 Studies have shown a decrease in BDNF serum levels to negatively correlate with cognitive decline and deficits in long-term potentiation and memory in dogs. Feeding dogs a diet supplemented with antioxidant-rich phytonutrients has been shown to significantly increase serum levels of BDNF compared to dogs receiving a non-enriched diet, and has been proposed as a viable strategy to improve memory and learning, and counteract cognitive decline with aging.9,10


Working dogs: how diet can help reduce muscle fatigue

Exercise-induced oxidative stress contributes to increased muscle fatigue and muscle fibre damage, reduced performance, and eventually impairment of the immune system.

A randomised, placebo-controlled, crossover trial was conducted to evaluate the potential ability of an antioxidant-supplemented kibble diet to control the oxidative stress and general health status of therapy dogs involved in animal-assisted intervention programs. The antioxidant formulation used in the study was based on grape seed extract, quercetin, blueberry, resveratrol, strawberry and blackberry dried extracts.

The study concluded that feeding therapy dogs a balanced kibble diet supplemented with antioxidant-rich phytonutrients may be a valid approach to restoring good cell metabolism and neutralizing excess free radical damage due to oxidative stress before and after physical work.11


Anxiety, stress and aggression: how diet can impact a dog's behaviour

Stress, anxiety or any behavioural disorders can easily upset the stable neurotransmitter and hormone balance necessary for normal canine behaviour. For example, low plasma serotonin concentrations have been associated with aggressive behaviour, while impulsivity has been associated with reduced circulating levels of both dopamine and serotonin.12

A randomised controlled trial assessing neuroendocrine blood parameters in dogs with behavioural disorders related to anxiety, stress and aggression found that dogs fed a kibble diet enriched with phytonutrients (pomegranate, valerian, rosemary, linden, hawthorn, L-theanine (from green tea)) and the amino acid L-tryptophan for a period of 45 days, had significantly increased levels of serotonin and dopamine (used as behavioural markers) and significantly decreased levels of cortisol and norepinephrine (used as stress markers) compared to dogs fed kibble alone.12


Cancer: how diet can help reduce the risk of cancer in dogs

Nutritional intervention can be a powerful tool for controlling malignant disease and there is increasing evidence that connects the contemporary kibble diet with increased prevalence and incidence of cancer in dogs.13

In a study conducted to evaluate the effects of vegetable consumption on the risk of developing bladder cancer in Scottish Terriers, it was found that dogs consuming vegetables at least 3 times per week, in addition to their standard kibble, experienced a reduction in cancer risk of between 69-88% compared to dogs consuming kibble alone. The vegetables highlighted in the study included cruciferous, green-leafy, yellow-orange, tomatoes, green beans, green peppers, celery and peas.14


Fibre: how fibre can help lower cortisol levels

While previous research has clearly established that probiotics can alter overall health, including brain function, mood and behaviour; studies are now showing similar benefits from prebiotics – the plant fibre found in many fruits and vegetables that act to promote the growth of beneficial bacteria in the gut.

One of the ways that prebiotics have shown significant neurobiological benefits in the human brain is by lowering cortisol levels and the body’s stress response,15 and evidence is mounting that this may apply to our dogs as well.16


In summary: how fruits and vegetables can benefit your dog

While it is true that dogs do not have a specific requirement for carbohydrates (such as found in plant matter) in order to survive; as a facultative carnivore, the dog is able to utilise carbohydrates to a much larger extent compared with the more carnivorous wolf.17

Phytonutrients are an invaluable source of antioxidants and play a significant role in supporting the overall health of our dogs. Many fruits and vegetables are suitable for dogs to eat and this article has barely scraped the surface of the myriad benefits that plant matter can offer our dogs. 

If it’s not something you’re currently doing or recommending to clients, I urge you to consider supplementing the standard kibble diet with small amounts of fresh plant matter as a safe, easy and medication-free first-line approach to the treatment of a range of health and behavioural issues.


Examples of suitable plant matter for your dog

As dogs do not have the necessary digestive enzymes to break down the outer walls of plant cells, the best ways to prepare plant matter before feeding it include: finely chopped, grated, pulped, mashed, liquidised or slightly cooked.

Starchy carbohydrates (such as potatoes, pumpkin and parsnips) should always be cooked before feeding.



·       Parsley

 ·       Green pea sprouts

 ·       Spinach

·       Broccoli

·       Dandelion greens

·       Celery

·       Carrots

·       Asparagus

·       Brussels sprouts

·       Mushrooms

·       Cauliflower

·       Cucumber

·       Capsicum

·       Peas

·       Tomato (fully ripe)

·       Artichokes

·       Asian greens

·       Parsnip

·       Green beans

·       Zucchini

·       Pumpkin

·       Garlic (v. small amt)

·       Avocado (flesh only)

·       Sweet potato

·       Beetroot

·       Cabbage

·       Potato

·       Eggplant

·       Lettuce

·       Squash



·       Berries

 ·       Kiwi fruit

 ·       Apple

·       Pears

·       Pomegranate

·       Papaya

·       Citrus fruits

·       Pineapple

·       Banana

·       Mango

·       Watermelon

·       Peaches

·       Strawberries

·       Pitted cherries

·       Paw paw


Nuts and seeds (ground, small amounts only)

 ·       Almonds

·       Pine nuts

 ·       Cashews

·       Sunflower seeds

·       Flaxseeds

·       Pumpkin seeds

·       Chia seeds (soaked)

·       Hemp seeds

·       Sesame seeds


Or, if you have a dog that isn't eager to eat their fruits and veggies, you can always add the CanineCeuticals Organic Super Greens to their meals for a super convenient, yet potent, boost of antioxidant-rich phytonutrients.

Click to buy now: Organic Super Greens


CanineCeuticals - Organic Super Greens


You may also be interested in reading our article on Good Health Begins in the Gut for an insight into how diet can impact and benefit your dog's wellbeing.


Prefer to learn by listening? Then check out Narelle's podcast episode on The Link Between Diet and Behaviour in Dogs here.  


  1. Mugford, R.A., The influence of nutrition on canine behaviour. J Small Anim Pract, 1987. 28(11): p. 1046-1055.
  2. Giampieri, F., Special Issue "Phytochemicals in Health and Disease". Nutrients, 2018.
  3. Spencer, S., et al., Food for thought: how nutrition impacts cognition and emotion. NJP J Sci Food, 2017. 1(7): p. 1-8.
  4. Gupta, C. and D. Prof, Phytonutrients as therapeutic agents. J Complement. Integr. Med, 2014. 11(3): p. 151-69.
  5. Winiarska-Mieczan, A., et al., The Role of Dietary Antioxidants in the Pathogenesis of Neurodegenerative Diseases and Their Impact on Cerebral Oxidoreductive Balance. Nutrients, 2020. 12(435): p. 1-32.
  6. Chapagain, D., et al., Cognitive Aging in Dogs. Gerontology, 2018. 64(2): p. 165-171.
  7. Cotman, C.W., et al., Brain aging in the canine: a diet enriched in antioxidants reduces cognitive dysfunction. Neurobiol Aging, 2002. 23(5): p. 809-18.
  8. Miranda, M., et al., Brain-Derived Neurotrophic Factor: A Key Molecule for Memory in the Healthy and the Pathological Brain. Frontiers in cellular neuroscience, 2019. 13(363): p. 1-25.
  9. Sechi, S., et al., An Antioxidant Dietary Supplement Improves Brain-Derived Neurotrophic Factor Levels in Serum of Aged Dogs: Preliminary Results. J Vet Med, 2015. 2015: p. 1-9.
  10. Fahnestock, M., et al., BDNF increases with behavioral enrichment and an antioxidant diet in the aged dog. Neurobiology of aging, 2012. 33(3): p. 546-554.
  11. Sechi, S., et al., Oxidative stress and food supplementation with antioxidants in therapy dogs. Canadian journal of veterinary research = Revue canadienne de recherche veterinaire, 2017. 81(3): p. 206-216.
  12. Di Cerbo, A., et al., Effects in dogs with behavioral disorders of a commercial nutraceutical diet on stress and neuroendocrine parameters. Vet Rec, 2016. 180: p. 1-7.
  13. Gentzel, J.B., Does contemporary canine diet cause cancer?; A review. Vet World, 2013. 6(9): p. 632-639.
  14. Raghavan, M., et al., Evaluation of the effect of dietary vegetable consumption on reducing risk of transitional cell carcinoma of the urinary bladder in Scottish Terriers. JAVMA, 2005. 227(1): p. 94-100.
  15. Schmidt, K., et al., Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers.Psychopharmacology, 2014. 232.
  16. Mondo, E., et al., Role of gut microbiota in dog and cat's health and diseases. Open Vet J, 2019. 9(3): p. 253-258.
  17. Axelsson, E., et al., The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Nature, 2013. 495: p. 360.


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