Plenty of pet owners suspect (or know) that kibble is bad for dogs. And the same goes for canned dog food too. However, the main reason my own dogs are on a raw diet is not because of additives, cheap ingredients, or the many other issues we can level in the commercial pet food industry. An important reason why kibble is bad for dogs is glycotoxins.
In short, both dry and wet dog food is making our dogs sick, especially as they get older. And the main reason is to do with the same compounds in highly-processed human foods that make us sick too. Now the pet food industry has done precious few studies on this, but the emerging research is pretty worrying. Let’s dive into all you need to know about glycotoxins in dog food.
What are Glycotoxins or AGEs?
Glycotoxins, also called Advanced Glycation End-products (AGEs), are compounds that occur when a fat or protein becomes “glycated” in a chemical reaction with sugar. Some of them the body makes itself, but others you get through a diet when you eat highly-processed and heat-treated food.
The term “glycated” means that a protein or a lipid (fat) gets a sugar molecule added to it. It happens in a chemical process that usually takes place between sugars, fats, and proteins. Advanced glycation end products are biomarkers (a sign found in blood tests) of aging and many degenerative diseases.
In the diet, they’re usually the result of the Maillard reaction (1), which is the chemical process that causes “browning” in food, such as when sugar caramelizes. Essentially, AGEs happen when food is cooked at high temperatures. In humans and animals, we link AGEs to conditions like:
- Food allergies
- Poor gut health
- Heart disease disease
- Hardening arteries
- Kidney failure
- Certain cancers (which is why feeding raw food is one of the ways to help prevent cancer in dogs)
- and many other and degenerative conditions.
So AGEs happen when food is processed at high temperatures, and we know that extruded dry dog food and wet canned food are cooked in extreme heat. It follows then that these same compounds that are linked to so many diseases in humans must also be making our dogs sick.
Another way that AGEs happen is when the body makes it itself as byproducts from breaking down food. These are called endogenous AGEs and high levels of carbohydrates (sugars) in the diet can cause far more AGEs in the body.
Now, dry extruded food (kibble) can contain up to 60% processed carbs. This amount of carbohydrates may increase the number of AGEs in the dog’s tissues, potentially damaging them and causing inflammation.
Remember, constant levels of inflammation in the body is a major contributor to most chronic diseases that dogs will suffer as they age.
Why Are Glycotoxins Often Ignored In Pet Food?
AGEs (glycotoxins) refer to many different compounds, mostly with names that are sure to give most of us a migraine. Names like carboxymethyl lysine (CML), or (wait for it) 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine… are enough to make the whole subject seem too complex.
But when pet food is tested for glycotoxins, it’s usually only for one or two compounds at a time and this can massively downplay the issue. For instance, studies may only test for the toxin called acrylamide, a human carcinogen.
These studies suggest that acrylamide in mass-produced canned and dry food exists at around.02 to 0.40 mg per kg dry matter. Conveniently the pet industry then deduced that anything below 7 mg acrylamide/kg dry matter is probably “harmless” (2). How they arrived at this conclusion when the long-term safety is still unproven is anybody’s guess.
So the emphasis here is on the word “probably .” Also, as acrylamide stays in the tissues, is eating it daily for years really safe?
Pet food research often tests for just one or two AGEs and then concludes (with limited or no evidence) that it exists in “safe amounts.” While we are (highly) skeptical of that claim, the bigger issue is what about the tens, if not hundreds, of other AGEs that also exist in heat-processed dog food?
Glycotoxins In Dog Food And The Link To Disease
A doctoral dissertation in 2020 was one of the few studies to actually measure AGEs in four different kinds of dog food (3). Predictably, canned food had the highest levels, probably because canned food is cooked at the highest temperatures.
Extruded dry dog food (kibble) followed closely with high AGE levels. Dehydrated food had very little; predictably, raw food had the least disease-causing glycotoxins.
Other findings include the following:
- Dogs eating extruded dry food may take in more acrylamide than adult humans. Despite it being labeled at supposedly “safe” levels, this is still worrying.
- In older dogs, AGEs build up in the brain’s neurons (5) and in the heart’s left ventricle. This may play a role in senior heart disease and dementia.
- In three recorded cases, dogs with high levels of AGEs in their system developed hard arteries (6).
- Pets are estimated to eat up to five times more heterocyclic amines daily in dry and canned pet food than humans. In rat studies, heterocyclic amines are linked to leukemia, breast cancer, and gut, liver, and lung tumors.
- Other AGEs that show up in much higher levels in dog and cat food than in human food include carboxymethyl lysine (CML), fructose lysine, and hydroxymethylfurfural. CML plays a large role in liver and kidney disorders, as well as diabetes and aging. Fructolysine is connected to diabetes too. When fructolysine oxidizes, it turns into CML, meaning that there is probably more CML in dog food than we think, causing more free radicals and inflammation in the body.
One study tested pets eating different kinds of pet foods tested for carboxymethyl lysine (CML), carboxymethyl lysine (CEL), and lysinoalanine (LAL) (4). Predictably, it found that the more heat-processed their food was, the more of these AGEs were in the dogs’ system.
All of these are specifically linked to kidney failure. Is it any wonder that about 1 in 10 dogs suffer from renal disease?
RELATED: Read more about why kibble is bad for dogs …
Are AGEs More Dangerous To Dogs Than Humans?
So far, while the pet food industry can’t deny that glycotoxins exist in pet food, they can point to the lack of research on it as a reason to shrug it off. We simply don’t know exactly how dogs (or cats and other pets) absorb, break down, or excrete the glycotoxins in their food.
Because there are not enough long-term studies specifically linking, say, doggy dementia to CML in dog food, it’s easy to say the evidence does not exist – even though a study does show that CML accumulates in older dogs’ brains.
But common sense tells us if glycotoxins cause so much havoc in the human body, they will affect our dogs too. In fact, dogs probably have a lower tolerance for AGEs than humans. Why is this?
Firstly, we know that dogs and cats deal with toxins differently than humans do. For instance, humans can handle toxins in foods like grapes and raisins, chocolate and onions that are toxic to dogs. This is because humans evolved to break down and excrete these compounds safely. Meanwhile, dogs evolved to eat meat and had no reason to evolve to metabolize compounds in a raisin.
As humans evolved to eat more carbohydrates, we see how much our blood sugar levels respond to high-carbohydrate meals. While massive spikes in blood sugar may not be good for our health, it is a sign that our bodies are more capable of processing carbohydrates. This suggests we are probably more capable of eliminating AGEs from our body. After all, scientists think we began eating cooked foods between 1.8 million and 400 000 years ago.
This probably gave us a lot of time to get better at getting rid of glycotoxins from our food, even though highly processed food today is still extremely unhealthy for us.
But dogs only became domesticated around 30,000 years ago, so they certainly haven’t yet evolved to deal with the same load of processed carbohydrates. So there is good reason to believe that dogs will be more sensitive and vulnerable to glycotoxins in food than humans are.
How To Reduce AGEs/Glycotoxins In Your Dog
Of course, feeding your dog a balanced raw diet is the number one way to reduce dietary glycotoxins. But there are other things you can do. According to the Anti-A.G.E’s Foundation, you can also:
- Give your dog as much exercise as you can (depending on his physical ability).It seems that physical activity reduces all the macronutrients in the body that form glycotoxins.
If you cook dog food, then cook it at low temperatures, such as with a slow cooker. Use a thermometer to check the heat is as low as possible.
Or buy freeze-dried or dehydrated or air-dried food if raw feeding is not available. Freeze-dried food is not processed with heat, so retains the nutrients of raw food. Dehydrated or air dried foods are dried at low temperatures but do suffer some nutrient loss from heat.
The answer is yes, dry kibble is bad for dogs. Of course, we know this for many reasons, such as synthetic additives, low-quality nutrients, aflatoxins, and more. But glycotoxins are the main reason I don’t feed my dogs heat-processed foods. As they are linked to almost every disease, from dementia to cancer, canned or dry dog food is simply not a good investment in a dog’s long-term health.
- Van Rooijen C, Bosch G, Van Der Poel AF, Wierenga PA, Alexander L, Hendriks WH. The Maillard reaction and pet food processing: effects on nutritive value and pet health. Nutrition research reviews. 2013 Dec;26(2):130-48.
- Beynen AC. Acrylamide in petfood.
- Bridglalsingh S. Influence of Four Differently Processed Diets on Plasma Levels of Advanced Glycation End Products (Ages), Serum Levels of Receptor for Advanced Glycation End Products (Rage), Serum and Urine Metabolome, and Fecal Microbiome in Healthy Dogs. 2020. University of Georgia ProQuest Dissertations
- Palaseweenun P, Hagen‐Plantinga EA, Schonewille JT, Koop G, Butre C, Jonathan M, Wierenga PA, Hendriks WH. Urinary excretion of advanced glycation end products in dogs and cats. Journal of Animal Physiology and Animal Nutrition. 2021 Jan;105(1):149-56.
- Weber K, Schmahl W, Münch G. Distribution of advanced glycation end products in the cerebellar neurons of dogs. Brain research. 1998 Apr 27;791(1-2):11-7.
- Chiers K, Vandenberge V, Ducatelle R. Accumulation of advanced glycation end products in canine atherosclerosis. Journal of comparative pathology. 2010 Jul 1;143(1):65-9.