Why brown biscuits/kibble dog food is bad for your dog

Written by Dr Nick Thompson MRCVS Nick is a vet who's passionate about natural and unnatural nutrition and all things medicine. He qualified from Edinburgh University in 1992 with an Honours degree in Pathological Sciences and a Bachelor of Veterinary Medicine and Surgery. Currently, he's heading up his own veterinary practice, Holistic Vet, who take a special interest in evidence-based canine natural nutrition. Pure Pet FoodPure Pet Food are the experts in healthy dog food and healthy dogs featured in media outlets such as BBC, Good Housekeeping and The Telegraph. Working with high profile veterinary professionals and nutritionists, Pure Pet Food are changing dog food for the better. - Our editorial process

So why should you avoid feeding those little brown biscuits some call kibble or dry dog food? We see in this article that tinned and kibbled food were historically made not for health, but for convenience of manufacture, but they quickly started harming pets once introduced.

We see these highly profitable, ultra-processed foods going against the nutrition of all species of animal on the planet. We see they contain carcinogens because of high-temperature processing. We see a direct link from the increase in kibble dog food feeding to the current obesity epidemic in dogs in the UK and US. We finally look at the diarrhoea and other bowel problems that can go hand in hand with food sensitivities to ultra-processed foods.

A history of kibble dog food

Henry Ford, you could say he was responsible for canned pet food. He was arguably the most famous pioneer of the 'motor car'. His four-wheeled creations elbowed out the poor old horse as the main means of transport, and gradually there was an excess of redundant horses. Well, they had to put them somewhere, so in 1922 in the US, they put them in cans, called it Ken-L Ration, and it sold like hotcakes.

But canned 'dog meat' superseded an 1860 idea of 'dog biscuits'. James Spratt was really the godfather of processed food for dogs. He noticed that dogs in the port of Liverpool were living on ships biscuits. He took the idea and ran with it, creating Meat Febrine Dog Cake, which is ironic because he didn't use meat in it, just beef blood, to save money and use another waste product to turn a profit.

Tinned dog food and biscuits were set to steal the show until the second world war when meat, tin and steel were rationed. Oops!

Ralston Purina solved the problem when they came up with the idea of making dried, extruded dog food in the 1950s. They put cheap dog food ingredients through their shiny new high-temperature, high-pressure breakfast cereal 'extrusion' machines. Large sacks of dry, ultra-processed, ultra-convenient dog food were born. What could possibly go wrong?

Cats were the first ones to show problems. In the 1970s cats eating exclusively the new 'kibbled' diets were showing eye problems and heart disease at rates previously unheard of. It turned out to be the first taurine deficiency scandal.

Nowhere in this history of feeding cats and dogs (as cheaply as possible) is health mentioned. Price, convenience, profit margin, marketing, market share, cheap ingredients, yes, but health, no. Hippocrates of Kos could have told them they were making a profit at the expense of pet health when he wrote, two and a half thousand years ago, 'Let food be thy medicine'.

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Why is kibble dog food so bad?

Why do I think brown biscuits, kibble dog food, causes disease? Because it's ultra-processed.

Not only that, it's cooked at high temperature and pressure and is easy for some producers to hide poor quality ingredients or bamboozle with 'ingredients lists'.

Below is a diagram showing the extrusion process these ingredients go through when being kibbled.

Ultra-processed food. Is that a thing? Certainly is in the human food world. It's defined, in 2019, by Carols Monteiro and Geoffrey Cannon from the University of Sao Paulo, Brazil, in this way: 'Processes enabling the manufacture of ultra-processed foods include the fractioning of whole foods into substances, chemical modifications of these substances, assembly of unmodified and modified food substances, frequent use of cosmetic additives and sophisticated packaging'.

Cooking kills food. Drying and dehydrating preserves it, without the need for any additives, as we've known for thousands of years. Ultra-processed dog foods (kibbles, for example) can contain flavours, flavour enhancers, colours, emulsifiers, emulsifying salts, sweeteners, thickeners, and anti-foaming, bulking, carbonating, foaming, gelling and glazing agents. Real food neither requires or wants any of these artificial alterations.

Real foods are nutritionally superior because they have biochemical complexity, nutrients in natural form, food synergy between ingredients, higher antioxidant capacity and fewer heat-mediated toxins.

Cooking alters the nature of food, sometimes for the better, often for the worse. Applying heat, above 140 degrees centigrade, to carbs and proteins, always found in kibbles and biscuits, will result in carcinogen production, heat-medicated toxins, through the Maillard Reaction. Starches (carbs) and protein (meats) fuse to form Advanced Glycation End products and Acrylamide: carcinogens. A 2013 paper intitled 'Should veterinarians consider Acrylamide that potentially occurs in starch-rich foodstuffs as a neurotoxin in dogs?' pretty much sums it up for me. The Maillard Reaction does not happen with air-dried, dehydrated, raw or fresh food because preparation temperatures are moderated.

We know healthier dogs live longer and owners spend less on vet bills too; they don't get as many ailments, allergies or health complications.


Did you know that most kibbles contain 30-60% starchy carbohydrate? Yes, it's true. We, humans, are reducing our carb and sugar intake like it was going out of fashion, but the kibble-brigade have been, and continue to, hold their brown biscuits together with carb-glue. Cooked grains, pulses, maize and tapioca and the like hold the biscuits together preventing them from turning into powder in the bag.

Some authorities do not agree, but best selling authors like Dr. Jason Fung [The Obesity Code], Gary Taubes [Why We Get Fat and What to Do About It] and emeritus professor in the Division of Exercise Science and Sports Medicine at the University of Cape Town, Tim Noakes [The Lore of Nutrition - Challenging Conventional Dietary Beliefs] all condemn long term high carb diets.

The presence of lots of cooked carbohydrate in every kibble biscuit, every mouthful, every meal of kibble has a massive drive to promote fat storage in the body via chronic insulin over-production. The effect of this excess is, of course, an obesity epidemic. Sixty per cent of dogs in the UK are overweight or obese, according to Alex German, Royal Canin Professor of Small Animal Medicine at Liverpool University Vet School. Thirty years ago this figure was a fraction of what we see in dogs today.

Obese dogs can get orthopaedic disease, diabetes, abnormalities in circulating fat, cardiorespiratory disease, urinary disorders, reproductive disorders, neoplasia (mammary tumours, transitional cell carcinoma in the bladder), dermatological conditions, and anaesthetic complications. Frighteningly, the lifespan of obese dogs can be up to two years less than their trim contemporaries. Obesity rates had risen during the period since 1980 when kibble feeding took hold in the UK; funny coincidence, that.

Why isn't anyone doing anything about this horrible epidemic? Where are the authorities? FEDIAF, the pet food manufacturer federation for Europe and the UK don't have anything to say on carbs. In their 102 page Nutritional Guidelines of 2017, they mention 'carbohydrate' only seven times, and then, only in passing (Protein is mentioned hundreds of times on 41 pages, by contrast). In none of the seven mentions do they offer minimum or maximum quantities of carbohydrate to be fed. Astonishingly, 'dietary carbohydrates are not considered essential nutrients for dogs and cats', according to the National Research Council in the USA, the highest authority for small animal nutrition on the planet. And yet carbs are added to all kibbles and most tinned pet food all over the world.


Obesity is defined in humans as excessive white adipose tissue. Human epidemiologic data show increased disease issues with increasing body fat mass. The most commonly used measure of body fat in people is the body mass index (BMI: weight [kg] divided by height2 [m]). People are defined as:

Underweight (BMI < 18.5)

Normal (BMI = 18.5 to 24.9)

Overweight (BMI = 25 to 29.9)

Obese (BMI = 30 to 39.9)

Extremely obese (BMI above 40).

Individuals who are overweight or obese have an increased risk of cardiovascular disease and certain cancers and overall mortality.

Professor Alex German of Liverpool University, the King of Obesity in Dogs says, "Data from our pets are more limited, and the definition of obesity is more arbitrary. Dogs are considered overweight when their weight is more than 15% above ideal and are obese when their weight is in excess of over 30% of ideal. However, these criteria have not been confirmed with rigorous epidemiologic studies, and limited data exist on the definition of optimal body weight". Yes, that means we don't know exactly what the ideal weight for your pet is! But bear with me.

In vet medicine, we use weighing scales and 'ideal' body weight tables depending on the breed of dog. We are also increasingly using Body Condition Scoring - that is, measuring how much body fat the dog has, as well as merely measuring how many kilos they weigh. This makes a lot of sense. If you have a well-muscled and tall Labrador in perfect body condition weighing 40kg, this is very different from the short-backed, small, obese Lab who also weighs 40kg - this illustrates the limitations of just using scales.

In the UK, over 60% of dogs are considered to be obese or overweight. Obesity used to be considered an inconvenience and somehow cuddly and 'well, he's just got big bones' and other excuses. At a recent World Small Animal Veterinary Association One Health meeting, canine obesity was officially classified as a disease, which is consistent with its classification in people. It is considered a chronic illness - that is, a long term issue that needs to be addressed for the health and welfare of the patient.

In dogs, obesity is associated with osteoarthritis, type 2 diabetes, high blood pressure, heart and respiratory disease, kidney disease, cancer and more. This is really serious stuff if you want a healthy dog to live out their full life potential! And 6/10 dogs have this disease of obesity, mainly due to an inappropriate diet. Obese pets are 15-30% more expensive to care for over their lifetime.

When I talk to owners about obesity, they will often say 'Oh, yes, well, he hasn't been getting as much exercise recently'. This may be so, but science tells us that exercise is only a small part of body weight control, perhaps as little as five per cent, depressingly. Human nutritionists are known to warn, 'you can't outrun a bad diet'.

But all is not lost. Changing diet can influence body fat. Using conventional diets, unfortunately, the success rate, even with the most qualified university vets in the UK, is only 50% of dogs reaching target weight on any given diet and of those only half remaining at that weight!

Our experience with feeding a species-appropriate fresh or air-dried (which is essentially fresh) diet is much better.


Diarrhoea (Americans spell it Diarrhea, but pronounce it the same) is almost as common as obesity and frequently (but not always) associated with diet. All dogs can get loose stools (the definition of diarrhoea) after 'dietary indiscretion' (also known as raiding the bins or picking up offensive material off the floor on walks!). This short-term looseness usually sorts itself out with bland food for a few days. It can happen to air-dried, fresh, kibble, tinned and raw fed dogs, alike.

The more worrying issue is where the runny poos go on for some time - anything over two weeks or so is considered to be 'chronic' or long-term. You may be surprised to hear that a remarkably high number of dogs produce less than perfect stools, sometimes for years and years. Their owners are so used to seeing a sticky mess coming out of their dog. They assume it's normal. It's not.

At my practice, we use the Thompson Stool Score system to assess, note and communicate about stool quality. Here's an introduction:

The Thompson Stool Score for Dogs and Cats

0 - Water/Soup

3 - Thin, but will hold together on the ground without dribbling everywhere — uncooked thin cookie dough.

5 - Blancmange - neither liquid or solid. Scoopable, but leaves a mess.

7 - Formed but soft. Very soft sponge cake. Not pickupable, but perhaps cleanly scoopable.

10 - Perfect cigar or torpedo. Pickupable between two fingers.

It's that simple. (I find food analogies are useful because they are so memorable, if unappetizing!) You can add helpful detail like colour, smell and uniformity (lumpiness) for added information. Beware of making things too complicated.

The most common cause of chronic diarrhoea and the easiest to fix is due to dietary intolerance to one or more components in the diet. If you're feeding a kibble or a tinned formula, there are usually ten or more ingredients, and you can't separate them. If you feed a complete, air-dried or fresh food, you are more in control of what you feed your pet. You can strip the diet down to one protein source (meat) at a time and see what effect this has on stool quality. It's a straightforward, but effective way to investigate these things yourself.

Wheat, beef and chicken are the most common foods that cause sensitivity/intolerance. Why? Because they are the most commonly used in foods and have been for decades.

If your dog or cat produces a 7/10 stool, you might be ok with this, but if you think about it, they are 30% down on a perfect poo (if the poos were 5/10, they'd be 50% down on perfect). This either means they have a degree of inflammation in the gut, so the absorption of water from the stool is impaired, or their microbiome (the bugs that are essential to health and gut vitality) is disordered. Of course, there are diseases like cancer, hepatitis and worms that can also give poor stool quality, so if you have any concerns, contact your vet who can run some tests to rule these more severe diseases out.

A simple consequence of loose or imperfect stools is that the anal glands tend not to be emptied and, when full, can cause your dog to 'scoot' or 'sledge' on their anus to relieve the itch/pain in the glands. Getting the diet right gets the stools right. Good stools squeeze the glands as nature intended - a self-cleaning system.

Finally - if your dog is producing stools with mucus, some pain or some streaks of blood, then colitis, inflammation of the colon, is most likely. This is common and is usually associated with exposure to inappropriate food for your particular pet. For example, if your dog is fine on beef, but they get mucus if fed even a little lamb, then they most likely have a mild lamb intolerance or sensitivity, and this meat should be avoided for at least six months.


In this article, we reviewed just a few reasons why not to feed ultra-processed kibble.

We see that tinned and kibbled food were made not for health, but for manufacturer and consumer convenience, but they soon, over the years, started harming pets.

We see kibbled and tinned foods contain carcinogens because of high-temperature and pressure processing. A direct link can be made from increased kibble feeding since the 1980s in the UK and US to the current obesity epidemic and all the resulting disease risks in dogs.

We review diarrhoea in dogs, how to measure and keep an eye on your dog's stools and discuss other bowel problems that can go hand in hand with food sensitivities to ultra-processed foods.

We also talk about how an air-dried, fresh diet is a great healthy alternative to the ultra-processed kibble diet. Learn more about how an air-dried diet can help your dog.

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