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Oxidative Stress and Antioxidants: A Beginner’s Guide for Humans and Dogs

You’ve probably heard the buzzwords’ oxidative stress’ and ‘antioxidants,’ and maybe you know antioxidant-rich foods are great for you. But what does all of this mean for your dog’s health? In this blog, Dr Nick Thompson, holistic vet, breaks down the essentials of oxidative stress, the power of antioxidants, and how they play a vital role in keeping your dog healthy and thriving.

Dr Nick Thompson

Author: Dr Nick Thompson
BSc (Vet Sci) Hons, BVM&S, VetMFHom, MRCVS

Oxidative Stress and Antioxidants: A Beginner’s Guide for Humans and Dogs

Did you know that oxygen is actually really toxic? Yes, that’s right, animal life, including us humans, is wandering around in a soup of oxygen exhaust fumes from plants! Luckily, with the help of ancient bacteria that hitched a ride in our cells billions of years ago, we use oxygen to drive the leading energy-producing factories in our mammalian bodies.

The trouble is that there is always a price to pay for handling this kryptonite-like oxygen molecule in our cells. It’s called ageing. Metabolic diseases such as obesity, cancer, organ dysfunction, and cognitive decline are the result.

OK, that’s quite a lot to pack into the first paragraph of a beginner’s guide, so let me explain. In this section, I’ll explain oxidative stress, its origin, and how it can affect your dog. In the second half, I’ll explain antioxidants, where you can find them, and what they do. Read on!

Oxidative Stress

Oxidative stress is just a fancy name for the damaging effects of metabolising oxygen for energy. If you think of a rusting iron object left out in the rain for years. Then you’ve got a pretty good picture of oxidation, the corrosive, damaging effects of environmental oxidative stress on ferrous materials.

We and our dogs aren’t made of metal, but the detrimental impact of oxidative stress to our flesh and blood is similar.

The mammalian equivalent of rusting is ageing, as I’m sure all my more mature readers will ruefully recognise. Humans and dogs have to make energy to survive. The primary process for creating energy is the formation of arguably the most crucial molecule in the body – adenosine triphosphate or ‘ATP’ to its friends.

Believe it or not, If you gathered all the ATP you or your dog made each day and weighed it, it would be about half your or their body weight. Yes, you make half your body weight every day in this energy molecule!

So why don’t we ridiculously increase our weight daily? The answer is, of course, that the energy molecules made every day are used up in motion and metabolic processes. How clever is that?

All good things have downsides. The downside of producing life-giving ATP is that the process produces super-reactive molecules called ‘free radicals’ or ‘reactive oxygen species, ROS’. You could call these molecules’ oxidants’, but nobody does.

Cleverly, the body produces (or eats) antioxidants, which mop up these dangerous little blighters before they can do damage so that we can all live long, healthy lives.

I like the image of 20 people standing in a line and a scorching jacket potato being placed into the hands of the first person. That person can only keep the hot potato (the free radical) in their hands for a second or two before they have to turn and pass the potato to their neighbour. So, the spud goes down the line and cools as it passes from person to person.

This is how antioxidants function; the most potent antioxidants, melatonin and glutathione, for example, go in first and then pass the slightly weakened free radical to the next antioxidant in the chain, which will then pass to the third and 4th antioxidants in the chain, diffusing the toxicity of the free radical as it travels down the line.

Logic tells us that if you don’t produce enough antioxidants, eat enough antioxidants in your diet, or produce too many free radicals, then tissue damage will occur. In dogs, this manifests as organ disease, cancer, cognitive decline, aching joints, muscle stiffness, general slowing down, and all the painful processes we see as our dogs age. 

Exogenous (environmental) oxidative stress

The list of environmental (exogenous) oxidising toxins is almost infinite. One way to think about that limitless list is to think of all the things that are ‘bad’ for you. Think about ultra-processed food, sugars, natural and man-made pollution, microplastics, pesticides, herbicides, and the bevvy of delightful modern agricultural and industrial chemicals we meddle with daily (or apply to our beloved dogs).

Also on that list, surprisingly to some, are all pharmaceutical medicines. Yes, the drugs we use to help heal our dogs all have visible or invisible dark sides. For example, antibiotics can be toxic in and of themselves (apart from disrupting the gut microbiome).

Trimethoprim sulphonamide drugs, for example, can induce dry eye in dogs if given too long. Non-steroidal anti-inflammatories can reduce pain and inflammation, but they also cause damage to the lining of the stomach and gut, among other body tissues.

Many have hailed vaccines (along with surgery and antibiotics) as humanity’s most outstanding medical achievement. This may be the case, but the damage they are capable of is undeniable. Mercury and aluminium are two examples of toxic metals found in vaccines that cause long-term tissue damage through oxidative stress.

Endogenous (bodily) causes of oxidative stress

Excess inflammation, whether caused by viral or bacterial infection, trauma, autoimmune disease, poor sleep, or stress, can cause the body to overproduce damaging reactive oxidative molecules. Controlled inflammation is generally good, but disease results when it’s too intense or lasts too long.

When dogs eat kibble or other high-starch foodstuffs, their blood sugar levels increase, unlike dogs eating starch or grain-free raw dog food or a fresh diet [1]. This is similar to humans eating ultra-processed food or having too much sugar. Excessive sugars are combined in the canine and human bodies with proteins forming ‘advanced glycation end products’, the so-called AGEs. This is a good acronym for these sugar-protein complexes because they promote ageing by damaging enzymatic metabolic pathways. They also gum up enzymes with antioxidant roles, leading to oxidative stress. [2]

I explore the topic of kibble in more depth in my blog, Why I Refuse to Feed Kibble. Raw feeding offers numerous benefits for your dog’s overall health, and it’s one of the most impactful changes you can make to support longevity and vitality. If you’re considering making the switch, ProDog’s Beginners Guide to Raw Feeding is a fantastic resource to help you get started, with practical advice to ease the transition.

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Nutrient antioxidants

Antioxidants are like nature’s firefighters in the body. Their job is to put out small fires and sparks before they spread further into the body, causing tissue damage and disease. They are found in large quantities in real food and rarely in ultra-processed foods.

Vitamin antioxidants

Retinol (Vitamin A) found in cheese, eggs, oily fish, milk and yoghurt, is a potent antioxidant, especially in vision, growth, immune function and reproductive health processes.

Vitamin C is perhaps the best known and best-loved vitamin. Everyone knows it’s found plentifully in citrus fruits, red and green peppers, strawberries, and, for example, kiwi fruit.

Most people don’t know that pasture and regeneratively raised meats also have a significant vitamin C content. Vitamin C, as an antioxidant, also helps protect cognitive functions such as thinking and memory and is critical to maintaining skin and immune health.

B vitamins 1, 2, 6, 9 and 12 (thiamine, riboflavin, pyridoxine , folate and cobalamin) are significant on the antioxidant scene. Like most antioxidant vitamins, they are involved in energy, red blood cell, brain, DNA, neurotransmitter, and hormone production. Deficiency leads to anaemia and mouth sores and has been associated with breast cancer in women (thiamine). Riboflavin has reversed liver cancer in animal models.[3]

B vitamins are unique among antioxidant vitamins because they are water-soluble. This is protective because giving our dogs an excess of B vitamins is virtually impossible as any excess is eliminated in urine. B vitamins are plentiful in fresh fish, poultry, meat, eggs, dairy products, brewer’s yeast and superfoods such a chlorella. There are also significant quantities in leafy green vegetables, which I always add to raw dog food recipes.,

Dog gut health is critical to overall health and happiness. Most of the canine microbiome is found in the gut, especially the large intestine. It does many things for the canine body, including producing fatty acids and breaking down nutrient molecules. The most interesting contribution of those gut bugs is in the production of B vitamins, especially B9 and B12.

Vitamin D is usually associated with strong and healthy bones. It is also critical as an antioxidant, helping muscle movement, nerve connections, and immune health against, for example, coronaviruses. It’s found in salmon, mackerel, sardines, herrings, egg yolks, red meat, and liver.

The more I learn about vitamin D’s hundreds of functions, the more I consider it the king of vitamins. 

Finally, vitamin E, which many people know as an antioxidant because cosmetic manufacturers forever tell us how wonderful it is as an antioxidant, making our human skin youthful, glowing, and wrinkle-free (if you’re lucky). We can find vitamin E in nuts and seeds and green vegetables such as spinach and broccoli for dogs.

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Mineral antioxidants

Selenium and zinc are the best-known trace minerals with potent antioxidant activity. Selenium helps immune function by boosting white blood cells. It is critical in synthesising thyroid hormones and even the production of DNA in the nucleus of all cells. It is rich in organ meats, seafood, beef, chicken, cottage cheese and eggs.

Zinc is equally replete with superpowers. It’s essential for embryonic pup development, helps fight bacteria and viral infections, and is vital for DNA and protein synthesis. Low zinc diets are associated with poor wound healing and can even lead to the loss of taste and smell. Luckily for dogs, it’s found in many yummy foods like oysters, poultry, red meat, organ meat, nuts, and dairy products.

Manganese is often overlooked in discussions of antioxidant micronutrients. But manganese is up there, along with copper, as a vital yet unsung antioxidant mineral hero. Dogs cannot produce manganese so it must be obtained through their diet or via a supplement. Manganese is critical for bone health, blood clotting, immune function, energy production, and brain and nerve function. It’s found in shellfish such as mussels, and also:kelp, sardines, beef liver, hemp seeds, pumpkin seeds and spinach.

Copper is found in oysters and other shellfish, nutritional yeast, and dark leafy greens and is incredibly bioavailable in organ meats such as kidney or liver. The benefits of copper to canine health are best illustrated when we look at problems associated with copper deficiency. These include a tendency to bone fractures, low body temperature, low red and white blood cells in the bloodstream, irregular heartbeats, thyroid problems and changes in pigmentation of the fur and skin.

Other nutritional antioxidants

N-acetyl cysteine (NAC) is often described as a conditionally essential amino acid because it can be synthesised from other amino acids. Nutritional NAC is essential if methionine and serine are low in the diet. Plant-based diets are low in methionine, which is why I reject plant-based diets for dog nutrition.

NAC is responsible for replenishing one of the most potent antioxidants in the body, glutathione. This is partially why NAC is effective in treating liver damage and 100% effective in paracetamol poisoning if given within eight hours.

Raw-fed dogs are rarely deficient in amino acids if they eat various meat and organs, so NAC supplementation is seldom required. Sources of cysteine include, freshly ground sunflower seeds (not sunflower oil!), eggs, cheeses, and yoghurts.

Quercetin

You’ve likely heard of quercetin as a natural antihistamine. But what you probably haven’t heard is that this remarkable flavonoid which is found in kale, broccoli, blueberries and tomatoes, especially cherry tomatoes, is also a pokey antioxidant.

Many scientific papers suggest it may help prevent human heart disease [4] and cancer. In addition, it is known to have anti-inflammatory, antiviral, anti-diabetic, and anti-obesity properties and may protect against neurodegenerative disease. [5]

Alpha lipoic acid

Alpha lipoic acid, or lipoic acid, can be manufactured in the body. However, it is also available in red meat, organ meats, and brewer’s yeast. It is a powerful antioxidant, but unlike vitamins A, D, and E, which can only work in fatty environments, or vitamin C, which can only work in water-based systems, alpha lipoic acid can be active in both.

In humans, ALA helps regulate raised blood sugar levels in diabetic patients. It has been used for many years in Germany as a treatment for peripheral neuropathy. Alpha lipoic acid can pass easily through the blood-brain barrier. It may help with brain and nervous tissue oxidative stress. Therefore, in humans, it may have a role in the treatment of stroke or other free radical disease, such as dementia.

Further, some studies suggest it may help treat glaucoma. In contrast, others suggest it might be helpful in binding toxic metals such as mercury and arsenic that act as free radicals. In humans, it is even considered for erectile dysfunction, ear infections, and cancer.

Final thoughts

All in all, I hope you can see how elegant the antioxidant story is. Antioxidants mop up the toxic exhaust products of vital energy production within the body. The body is clever enough to make many antioxidants to fulfil this role but relies on a plentiful food supply.

It’s a massively efficient system, but it could be better. We and our dogs age and eventually fail. Other factors certainly affect ageing. For example, our DNA telomeres shorten with every cell division, condemning us to old age frailty, but the ravages of antioxidants sure have an impact as the years go by.

What do we do? For ourselves, we should eat foods rich in antioxidants and avoid the multitude of modern pro-oxidant toxins in the environment, like ultra-processed, ultra-convenient food. We should do the same for our dogs.

Sometimes, controlling the dog’s environment is easier than controlling our own.

Taking a natural approach to parasite prevention to eliminate the need for harsh treatments is one way to protect ourselves, our families, and our dogs from oxidative stress. Meanwhile, feeding raw dog food or adding dog vitamin and mineral supplements are simple steps to add more antioxidants to the diet.

ProDog’s Revive supplement is packed with antioxidant ingredients such as green tea, NAC and chlorella. ProDog’s Digest containing Astaxanthin (a powerful antioxidant), parsley leaf, aloe vera and more are just two examples of simple ways to add more antioxidants to a dog’s diet. Plus, if you need a hand with your dog’s diet you can contact ProDog’s expert team for free, personalised canine nutrition advice.

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References

  1. Moore Robin , Anturaniemi Johanna , Velagapudi Vidya , Nandania Jatin , Barrouin-Melo Stella Maria , Hielm-Björkman Anna (2020). Targeted Metabolomics With Ultraperformance Liquid Chromatography–Mass Spectrometry (UPLC-MS) Highlights Metabolic Differences in Healthy and Atopic Staffordshire Bull Terriers Fed Two Different Diets, A Pilot Study. Frontiers in Veterinary Science VOL7. DOI: 10.3389/fvets.2020.554296
  2. Zhang, L., Wen, P., Zhang, J., Xia, C., Xu, J., Xu, H., Cui, G., & Wang, J. (2023). Effects of exogenous advanced glycation end products on oxidative stress and renal injury in healthy mice. EFood, 4(4), e105. Doi:10.1002/efd2.105
  3. Miller EC, Miller JA, et al. Correlation of the level of hepatic riboflavin with the appearance of liver tumors in rats fed aminoazo dyes. J Exp Med. 1948 Jul;88(1):89-98. doi: 10.1084/jem.88.1.89. PMID: 18871881; PMCID: PMC2135806.
  4. Egert S, Bosy-Westphal A, Seiberl J, Kürbitz C, Settler U, Plachta-Danielzik S, Wagner AE, Frank J, Schrezenmeir J, Rimbach G, Wolffram S, Müller MJ. Quercetin reduces systolic blood pressure and plasma oxidised low-density lipoprotein concentrations in overweight subjects with a high-cardiovascular disease risk phenotype: a double-blinded, placebo-controlled cross-over study. Br J Nutr. 2009 Oct;102(7):1065-74. Doi: 10.1017/S0007114509359127.
  5. Watson, R. R., Preedy, V. R., & Zibadi, S. (Eds.). (2018). Polyphenols: Mechanisms of Action in Human Health and Disease (2nd ed.). P. 361-392. Academic Press.

Image credit: Camilo Fierro on Unsplash 

Image credit: David Boca on Unsplash 

Image credit: amoon ra on Unsplash 

Image credit: andrew welch on Unsplash 

Image credit Caleb Carl on Unsplash 

Dr Nick Thompson

BSc (Hons) Path Sci., BVM&S, VetMFHom, MRCVS. Founding President of the Raw Feeding Veterinary Society. Petplan Vet of the Year Nominee 2009, 2015, 2017, 2018 & 2020. The practice of the Year Nominee 2018.

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