Most Dangerous Ingredients in Dog Foods

Dog food can cost a pretty penny.

While some pet owners may associate the higher cost of pet food with higher quality dog food ingredients, in some cases, this line of thinking needs to be questioned.

Believe it or not, pet food companies have used dangerous ingredients in dog food in the past and present.

Not all dog foods are created equal, and expensive dog food brands certainly are not always made with the best ingredients, either.

Unfortunately, there are pet food manufacturers, companies, and brands out there that let the potential for profit overshadow the need to provide high-quality, wholesome, and safe dog food.

There are good reasons to question who makes our pets' food and how they make it.

Some suspicious parts that make up dog food are far more harmful than others, and there are studies to prove it.

We are going to be going through the ingredients to avoid in dog food.

4 Ingredients to Avoid In Dog Food

1. Unsafe Artificial Preservatives

On a high level, consumers know that preservatives are used to preserve food.

However, what they don't know is that preservatives are often used to increase the shelf life of the fats and oils within dog food.

It's one of the things to watch out for when picking the best dog food brand.

But not all preservatives are bad.

Natural preservatives do exist, and they're much safer for pets than artificial ones.

Vitamin C (ascorbate) and Vitamin E (tocopherol) are available and used.

These are used to keep a dog's food from spoiling while stored.

These natural preservatives are considered safe for dogs and humans, and that's where the frustration sets in.

Due to the slightly higher cost of these raw natural ingredients, many dog food companies opt to use synthetic preservatives instead because they're cheaper.

The first suspect is ethoxyquin.

Studies have observed the negative effects (1) of ethoxyquin several decades ago. Yet, it's still being used in animal feed and often found on dog food ingredients list “because no alternative has been found yet,” according to some pet food manufacturers.

But the conclusions from the mentioned study are worrisome, and they read:

“Toxicity and mutagenicity of EQ were observed in in vivo and in vitro studies showing its potential harmful effects.”

So what is ethoxyquin, exactly?

The synthetic compound ethoxyquin is an artificial preservative. It's commonly used in dog foods, even after it has been noted to increase the risk of toxicity in dogs, but that is not its only attribute.

On top of that, ethoxyquin is also used as a pesticide.

Let that sink in for a moment: a substance used to effectively kill living organisms is used as an additive alongside other dog food ingredients.

In fact, ethoxyquin was originally developed (2) in the rubber industry to prevent the rubber from cracking due to the oxidation of isoprene.

It is still used in the rubber manufacturing process, where it is seen as a hardening agent.

The FDA has not let this go unnoticed and is investigating its role in developing liver and blood complications.

More studies were done on this.

Prolonged feeding of food containing ethoxyquin has been shown (3) to lead to liver cell death, with the following symptoms: decrease in physical activity, reduced urination activity, brown-colored urine (a clear sign that something is wrong with the liver or kidneys) and pale gums (which is indicative of bad circulation).

It clearly should not be included in any foods for humans or animals.

Other countries treat dog food ingredients with more care.

As we've seen in the country-wide comparison, Australia and the EU (European Union), for example, have taken it a step further and banned its use in dog food outright.

So, next time you shop for dog food, make sure to check the dog food ingredients list to see how many brands include this truly horrifying product.

You will be surprised and appalled.

More than ethoxyquin…

While ethoxyquin is currently under investigation and has been in the news as one of the first ingredients to be removed from animal feed, some other artificial preservatives found on dog food ingredients lists are still flowing freely.

Another set of dangerous preservatives in pet foods to be wary of are the BH brothers, already well-known to many dog owners and cat owners alike: BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene).

This one-two combination from hell is so bad that the WHO (World Health Organization) and the State of California have labeled both as being “suspicious cancer-causing compounds,” also known as carcinogens.

Here's a direct quote from WHO's classification of these preservatives (4):

“…an exogenous substance or mixture that alters the function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub) populations.”

However, just like ethoxyquin, both BHA and BHT can still be found in many commercial dog food brands and are yet to be properly investigated by the FDA/CVM and removed from circulation.

You'll find them on many dog food ingredient lists.

Next up is propylene glycol

Propylene glycol (PG) may sound familiar to people, and that's because most know it by its street name, anti-freeze.

And, just like the other compounds previously discussed, it is shockingly found among dog food ingredients to preserve fats and oils that many dogs find delicious.

Obviously, just because it may taste good for dogs doesn't mean it is good for their body.

In high doses, propylene glycol destroys erythrocytes (red blood cells), according to one study (5).

Another study with cats found (6) that propylene glycol causes anemia in animals, among other problems, and is not a safe preservative to use in pet foods.

From the study:

“These results indicated that PG cannot be considered innocuous even at concentrations consumed by cats eating commercial diets.”

2. Food Dyes and Coloring Agents

As a rule of thumb today, if it looks unnatural, then you're probably correct.

Real, healthy, and safe dog food ingredients are not supposed to be radioactive yellow or fluorescent red in color.

It has been observed that dogs consuming food with a lot of artificial coloring will take up those color compounds in their gastrointestinal tract, according to one study (7).

Brilliant Blue FCF, or Indigotine, another artificial color, has been shown to inhibit the growth of dogs.

The dogs eventually died of inter-current virus infections, which are theorized to have been the result of a decreased ability to fight off the infection due to the dog's compromised health.

Finally, there is evidence to suggest that regular intake of Indigotine may lead to the development of cancer (8).

The bright red dye known as Ponceau SX is a synthetic dye that, when included in dog chow at a 2% concentration, has led to the death of three of five dogs in a five-year clinically controlled study (9).

In the same family of dyes as Ponceau SX, Ponceau 3R has shown that including it in a dog's diet can have deleterious effects on the canine's liver after a mere 32 weeks of feeding, according to one study (10).

3. Rendering and Rendered Fat

Only in the dog food business can the conversion of waste animal tissue be spun into a good thing.

Pet food companies will proclaim that their inclusion of rendered fat into dog foods poses significant value for the owners and the dogs.

When has the addition of waste tissue ever translated into a value-add?

However, pet food manufacturers (and some vets) find a way to explain the process in a way that, at first glance, will make sense, but upon further assessment, it just doesn't.

When animals are processed at the abattoir, lean cuts of meat are usually separated from the animal's fats.

This fat along with oils and other animal products (as well as any form of fat that producers can get their hands on from deep fryer grease to offal) are then heated and “purified” into lard or tallow.

Rendered fat is usually mixed into dry dog food for moisture but also to make the meal palatable for the dog. This is why it's often found among dog food ingredients.

It has been observed that when oils and fats are listed as one of the first four in a dog foods ingredients list (meaning that there is a significant amount of it in the food), then there is a high probability that the dog will experience gastrointestinal (11) complications.

Not all fats are bad, however.

Animal meat that is usually consumed by dogs contains both proteins and fats.

However, it has been shown that when these natural fats are replaced with rendered fats, the dog demonstrates a host of negative reactions.

Loss of appetite, hair thinning, and loss, skin lesions, ulcers, and illnesses follow shortly after.

4. Animal By-products in Dog Foods

By-product, also known as meat meal, is the term given by the industry to all parts of an animal that is not muscle tissue.

Understandably, this is a long list of miscellaneous body parts, organs, tissues, and the like, including beaks, hooves, tails, hair, bone, gills, eyes, and teeth.

It can also include things such as diseased tissue and tumors.

Yes, you read that correctly – tumors.

Chew on that thought the next time you pick up a bag of kibble or chow and see that it includes chicken, beef, pork, lamb or fish by-products on the dog food ingredients list.

In fact, the FDA openly admits to allowing diseased animal tissue to be included in pet food manufacturing.

Susan Trixton from TruthAboutPetFood has inquired the FDA about this and received the following response (read the full letter in her article):

“Processed pet food, including pet food consisting of material from diseased animals or animals which have died otherwise than by slaughter, goes through a kill step, such as heat processing, which is designed to kill harmful bacteria.”

The confusing thing is that dogs can digest animal by-products.

Give a dog a chicken carcass, and it will eat it to its heart's content.

However, dogs were never meant to subsist on high concentrations of animal by-products the like of which are found in common commercial dog food and cat food brands.

While the animal by-products can be digested, there is significant variability in the total tract digestibility data – the digestibility of a substance throughout the entire process from the entrance to exit – according to research (12).

This may not seem like a big issue; indeed, it isn't for the dog food companies as they keep on using animal by-products and include them among other dog food ingredients, but these variations should never and would never exist were a dog given a nutritionally complete diet.

Animal by-products are not used in the production of commercial dog food because of their nutritional value.

They are used for one reason: they are cheap fillers that are cost-effective for the company.

The economics of the dog food industry states that using by-products as fillers among dog food ingredients will yield higher profit margins.

That's it.

Never was a dog's health and nutrition been in the minds of those who made this decision, and it shows.

By-products, while digestible (easily broken down), are not so easily absorbed into the dog's system.

This is unsurprising as parts like beaks, hair, and gills are very difficult, if not impossible, for a dog's body to convert into usable material (13).

Other Dangerous Dog Food Ingredients

Soybean oils

Soybean oil is arguably one of the biggest industries on its own because of its versatility.

It is used as a supplement from over-processed dog foods because it contains fats and essential amino acids.

However, too much consumption of soybean oil is unhealthy for dogs.

Other fat-soluble toxins

  • Arsenic
  • Mercury
  • Aflatoxin

Worst Ingredients in Dry Dog Food: Take Home Message

It's clear to dog owners and manufacturers alike that many of today's commercial dog food brands – some of which are very popular among pet owners – contain controversial and questionable, potentially dangerous dog food ingredients that may be, and sometimes even proven to be, toxic to dogs.

With dog food ingredients like ethoxyquin (a known pesticide), indigotin (a likely carcinogen), waste animal tissue, and spare or diseased animal parts being included in dog food, one must really wonder if dog food manufacturers care for the health, safety, and well-being of dogs.

Sure, their marketing and advertisements talk a big game, and their talking heads proclaim that they exist to better the lives of dogs.

But, the evidence in their ingredients suggests otherwise, and there's scientific research to support this conclusion.

In general, make sure to understand pet food labels and know what ingredients to avoid in dog food.

Be wary of companies that prioritize advertisements and marketing campaigns because you know that they aren't using those funds to research or purchase higher-quality ingredients.

READ NEXT: 3 Common Canine Diseases Linked To Dog Foods


Click here to see study citations and references

Footnotes, study citations, and further reading:

  1. Błaszczyk, A., Augustyniak, A., & Skolimowski, J. (2013). Ethoxyquin: An Antioxidant Used in Animal Feed. International Journal of Food Science, 2013, 585931.
  2. A. J. de Koning, “The antioxidant ethoxyquin and its analogues: a review,” International Journal of Food Properties, vol. 5, no. 2, pp. 451–461, 2002.
  3. I. Dewhurst. Pesticides Safety Directorate. Ministry of Agriculture, Fisheries and Food, Mallard House, Kings Pool, York, United Kingdom.
  4. Damstra T, Barlow S, Bergman A, Kavlock R, Van der Kraak G. Global Assessment of the State-of-the-Science of Endocrine Disruptors. World Health Organization; Geneva, Switzerland: 2002. WHO publication no. WHO/PCS/EDC/02.2.
  5. Weil CS, Woodside MD, Smyth HF Jr, Carpenter CP. Results of feeding propylene glycol in the diet to dogs for two years. Food Cosmet Toxicol. 1971 Aug;9(4):479-90.
  6. Christopher MM1, Perman V, Eaton JW. Contribution of propylene glycol-induced Heinz body formation to anemia in cats. J Am Vet Med Assoc. 1989 Apr 15;194(8):1045-56.
  7. HESS SM, FITZHUGH OG. Absorption and excretion of certain triphenylmethane colors in rats and dogs. J Pharmacol Exp Ther. 1955 May;114(1):38-42.
  8. Hansen WH, Fitzhugh OG, Nelson AA, Davis KJ. Chronic toxicity of two food colors, brilliant blue FCF and indigotine. Toxicol Appl Pharmacol. 1966 Jan;8(1):29-36.
  9. Davis KJ, Nelson AA, Zwickey RE, Hansen WH, Fitzhugh OG. Chronic toxicity of Ponceau SX to rats, mice, and dogs. Toxicol Appl Pharmacol. 1966 Mar;8(2):306-17.
  10. HANSEN WH, DAVIS KJ, FITZHUGH OG, NELSON AA. Chronic oral toxicity of Ponceau 3R. Toxicol Appl Pharmacol. 1963 Jan;5:105-18.
  11. Raghavan M1, Glickman NW, Glickman LT. The effect of ingredients in dry dog foods on the risk of gastric dilatation-volvulus in dogs. J Am Anim Hosp Assoc. 2006 Jan-Feb;42(1):28-36.
  12. Murray SM1, Patil AR, Fahey GC Jr, Merchen NR, Hughes DM. Raw and rendered animal by-products as ingredients in dog diets. J Anim Sci. 1997 Sep;75(9):2497-505.
  13. S. E. Allen, G. C. Fahey, J. E. Corbin, J. L. Pugh and R. A. Franklin. Evaluation of Byproduct Feedstuffs as Dietary Ingredients for Dogs. doi:10.2527/jas1982.5361538x

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Most Dangerous Ingredients in Dog Foods (Backed by Science)

Jennifer is a professional writer from Ontario with published work in newspapers and magazines all over the world. Now caring for two rescues, her biggest passion is dog care and nutrition, and uncovering the truths about the pet industry and products we use with our pets.