10 Bad Ingredients to Avoid in Dog Food – The Ultimate Guide

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Every pet parent knows the struggles of picking the right food for their furball.

As a responsible dog owner, you must have pondered several dilemmas regarding your dog’s nutrition.

Grain-inclusive or grain-free? Chemical preservatives or natural preservatives?

And what’s up with all those weird names? Every day, dog food ingredients seem to get new, hard-to-pronounce additions.

All of these might make you want to give up on researching the ingredients altogether. But you don’t — because you love your canine and want the best for them.

Well, let’s shed some light on controversial ingredients today, along with adequate research, and try to make the best choice for your canine friend.

10 Ingredients to Avoid in Dog Food

Some of these ingredients are responsible for massive recalls of pet food products. Others are still approved, even though there is mounting evidence that they may be bad.

And some ingredients seem to stir more controversy than warranted.

Let’s look at the most harmful ingredients to avoid in dog food at the moment.

1. Melamine

Most pet parents still remember the great melamine crisis of 2007. Many pet food products were recalled, and the list included a lot of well-known brands.

What is melamine, and why was the situation back in 2007 so serious?

Melamine is a small molecule containing nitrogen. It is commonly used in cooking utensils and plates production. Besides that, melamine is also a flame retardant and binding agent.

It can be used as a fertilizer, too — though not in the USA.

In 2007, several cats and dogs died because the pet food produced in China was contaminated with melamine.

FDA stated that melamine was found in the kidneys and urine of pets, as well as in food samples.

While melamine is not as toxic to dogs as some other substances, FDA disclosed that cyanuric acid — a melamine derivative — was also found. They suspected that cyanuric acid boosted the effects of melamine, leading to kidney failure in animals.

Usually, melamine can be found in wheat and rice products. Many dog foods include wheat and rice, so dog owners naturally want to know if they should avoid feeding these to their dogs. FDA says that some of the products on the 2007 list did not contain wheat nor rice, yet they had melamine.

2. Monosodium Glutamate (MSG)

MSG naturally occurs in certain food — like tomatoes and cheese.

MSG (monosodium glutamate) is derived from L-glutamic acid, a non-essential amino acid. In other words, we don’t need to get L-glutamic acid through food.

FDA considers monosodium glutamate “generally safe for use” (GRAS).

The problem is that there has been a lot of reports about the side effects of MSG over the years. Though most of these reports are anecdotal, they include unpleasant symptoms:

  • Headache
  • Weakness
  • Sweating
  • Flushing
  • Nausea
  • Facial pressure
  • Numbness, tingling, or burning in the face and neck
  • Rapid heartbeat
  • Chest pain

MSG has been used for decades as a flavor enhancer in human and pet foods.

When it comes to pet food, the problem is that MSG can sneak into the food without being explicitly mentioned on the ingredient list.

How? There are two ways:

  • Protein hydrolysis often produces MSG as a derivative
  • Natural flavor, as defined by FDA, can include hydrolyzed proteins

Some research suggests that up to 10% of MSG in your dog’s food won’t cause adverse effects. However, there hasn’t been extensive research on this topic and MSG’s long-term effect on canines.

3. Propylene Glycol

Propylene glycol is probably one of the most controversial ingredients on this list.

This colorless, odorless, and tasteless compound is found in anti-freeze. Still, it is also used in the food industry to prolong shelf life.

FDA considers it safe for use as an anticaking agent and antioxidant.

However, FDA also banned the use of propylene glycol in cat foods because it causes Heinz Body formation. They state that soft-moist cat foods contain it at levels which damage cats’ red blood cells.

Pet Poison Helpline cautions that large doses can even induce poisoning

In fact, back in 2015, a class-action lawsuit was filed against Purina Beneful. The main plaintiff claimed that Purina’s food, and specifically propylene glycol in it, had killed his three dogs and many others mentioned in this lawsuit.

The judge dismissed the lawsuit because the plaintiffs failed to provide enough evidence.

Still, all these cases beg the question: if this substance is banned in cat foods, and there has been a stir about its effect on dogs, should dogs keep ingesting it every day? We don’t think so.

4. BHA / BHT / Ethoxyquin

BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene) are synthetic antioxidants. They are mainly used as preservatives in food and cosmetics. Who said lipsticks weren’t (partially) edible?

According to the FDA, both BHA and BHT are permitted for human consumption.

Unfortunately, there is some evidence that both preservatives are carcinogenic.

According to one study report, BHA (butylated hydroxyanisole) is “reasonably expected to be a human carcinogenic.” This finding is somewhat challenged because the carcinogenic mechanism in rodents does not apply to humans.

Still, carcinogenic tests show that both BHA and BHT induce cancerogenesis, urinary bladder tumors, and thyroid cancer in rats and hamsters.

There haven’t been any studies on the impact of BHA and BHT on dogs, but we think it’s best not to risk it for the time being.

Ethoxyquin is another synthetic antioxidant commonly used in foods.

This additive was approved around 50 years ago. In terms of pet food, it conserves vitamins and prevents peroxide from forming in canned foods.

When it comes to ethoxyquin, FDA distinguishes between its use in human and pet foods. Ethoxyquin is approved for human consumption, but the animal feed is a different story.

Technically, FDA says that it can be used safely in animal food. However, since the 1990s, the FDA has received reports from dog owners about the adverse effects of ethoxyquin. These included allergies, skin irritation, organ failure, behavior problems, and even cancer.

In light of these, FDA established guidelines for ethoxyquin in animal feed. On its official pet food labeling page, FDA reiterates that there isn’t enough scientific data to name this ingredient an animal carcinogen and ban it.

That being said, FDA urged food companies to lower the amount of ethoxyquin.

5. Artificial Colors & Flavors

If you’ve ever wondered what Blue 2, Red 40, or Yellow 5 mean on the dog food label, you’re not alone. 

Is it a typo, a company code, or someone just thought this would make an ingredient list more colorful? Well, none of these — all of the above are examples of artificial colors.

AAFCO clearly defines which food dyes and flavors are allowed for use. Still, bear in mind that AAFCO does not have a regulatory function but merely recommends the nutritional profile.

Artificial preservatives, food dyes, and artificial flavors are sometimes added to make up for the shortcomings of dog food ingredients.

For example, suppose a food has cheaper ingredients that aren’t palatable. In that case, the manufacturer might add an artificial flavor to make it more enticing.

The research on the topic leaves a lot to be desired. One study reports mixed effects of food dyes — they can be either safe or raise the tumor markers

A myriad of studies is concerned with caramel, one of the most common food additives. One study says that caramel (a food additive) may protect DNA from oxidative stress. Another review mentions that caramel could be toxic to the immune system.

Still, pet owners feel naturally blue (pun intended) when their favorite dog food has artificial colors or flavors. Many pet food manufacturers are phasing them out, even though the science isn’t up-to-date just yet. We think you should do the same.

6. Nitrites / Nitrates / Sodium Nitrate

Nitrates and nitrites are compounds that contain nitrogen. They occur naturally in some foods and are added to preserve shelf life.

These compounds are considered dangerous and potentially lethal for ruminants, i.e. cattle, sheep, goats, camels, etc. Nitrates aren’t toxic in and of themselves, but they become toxic when converted to nitrites.

The toxicity symptoms include chocolate-brown blood, weakness, and collapse. This particular toxicity is hard to treat. High levels of nitrates and nitrites lead to death.

In 1997, several cats died in New Zealand, and two dogs experienced weakness and ataxia (lack of muscle coordination). The cats’ blood was chocolate brown, and the toxicology reports showed that the main culprit was sodium nitrate from pet food.

Both AAFCO and the EU have set the thresholds for nitrates in pet food. Still, it’s worth repeating that AAFCO’s guidelines are not regulations.

A study in Egypt (2015) analyzed 10 imported wet pet foods from USA, Germany, Czech, Brazil, and Thailand. The study found that all tested foods significantly overstepped the AAFCO guidelines.

Nitrates, and particularly sodium nitrate, are allowed in pet foods. Still, we believe that a lack of strict regulations means you should avoid foods with them.

7. Sodium Tripolyphosphate (STTP) / Sodium Hexametaphosphate

Both Sodium Tripolyphosphate and Sodium Hexametaphosphate are “generally recognized as safe” (GRAS) by the FDA.

Phosphates are used in dog foods to promote dental health. They are known to reduce tartar and fight plaque. 

If you look at dog foods focused on dental health, you will often find one of these two ingredients. They are also commonly found in dental sticks.

However, some dogs react poorly to them. They are known to be potential neurotoxins and skin irritants.

In fact, one study found that STTP induced vomiting in dogs. Furthermore, it decreased iron levels in the bone, liver, and spleen. It also caused bones to lose calcium.

So, while they may not be as bad as some other ingredients, exercise caution. It might be best to talk to a vet and determine the best way to pearly whites together.

8. Corn Syrup

High fructose corn syrup and regular corn syrup are sometimes added to pet food for flavor. They are both made from corn starch, though HFCS contains more fructose.

Corn syrup isn’t toxic to dogs — but it does have a very high sugar content.

HFCS is known to cause many health issues when taken regularly:

  • Obesity
  • Insulin resistance
  • Non-alcoholic fatty liver
  • Contributes to diabetes and other health issues

If that wasn’t enough, it’s probably addictive as well. One study found that HFCS changes dopamine regulation (the reward mechanism).

This means that your dog could, quite literally, become a sugar-junkie, to the point of rejecting other food.

Our advice? Stay away from it whenever possible.

9. Garlic / Onion Powder

Garlic and onion are known to be extremely toxic to dogs.

Allium family members (onion, garlic, chives, shallots, leek) can cause hemolytic anemia. Even in small amounts, they can result in the pet’s death.

But wait, aren’t we talking about the dog food ingredients here? Why would anyone use garlic and onion?

And in powder form, nonetheless — which can be up to 8 times more potent than fresh vegetables.

Is it surprising that some dog food manufacturers use onion and garlic powder as flavor enhancers? It sure was for us.

Don’t panic — these are always lower on the ingredient list and unlikely to hurt your dog.

American Kennel Club (AKC) claims that super tiny amounts might even be beneficial.

However, bear in mind that onion/garlic toxicity occurs at various levels, depending on the dog’s size, breed, age, and general health.

So, before feeding your dog a food with garlic or onion powder, it might be good to talk to your vet first. Or avoid it altogether.

10. Carrageenan

Carrageenan is a food preservative and thickener coming from red seaweed.

You might have seen this strangely-named ingredient on one of the wet dog food labels. And then on several websites saying it’s carcinogenic and extremely harmful.

The truth is not so simple. Carrageenan has been quite a controversial ingredient for some time, but the jury is still out on this one.

Many studies talk about gastrointestinal problems, ulcers, and other harmful effects on animals. Some of them link carrageenan to cancer.

The main debate is around the two forms of carrageenan: food-grade (undegraded) and degraded. The degraded carrageenan is believed to cause most health problems.

However, the real issue is whether the food-grade carrageenan is transformed into a more harmful form by gastric acid. One review claims this happens at a minimal and insignificant amount.

Furthermore, the same review mentions that adverse effects do not occur at levels lower than 5%. Seeing that carrageenan is lower on the ingredient list means that it’s unlikely to cause harm.

So, just to be safe, we would prefer carrageenan to be lower on the ingredient list. But the whole debate might have been a little blown out of proportions.

dog with empty bowl

Ingredients With Controversial Quality

In the section above, we have listed potentially harmful ingredients in dog food. Some are more dangerous than others, and others are epicenters of hot scientific and consumer debates.

The following ingredients may not be as harmful — unless your dog is allergic to them. Still, they often stir up controversy among pet parents (and always make a great topic here at Dog Food Heaven).

The main difference is that the majority of these ingredients are not synthetic. They are often natural leftovers of food production. So, the reason we are mentioning them here has more to do with the quality of the ingredients themselves.

Meat Meals / Bone Meals

AAFCO defines meat meals and bone meals as “the rendered product from mammal tissue.” 

Meat and bone meals should not include certain animal parts: hooves, hair, horn, manure, blood, and stomach contents. Except, AAFCO continues, “in such amounts as may occur unavoidably in good processing practices.”

Various meat and bone meals are often the first ingredients and main protein source in cheaper dog foods.

This prompted dog owners to label them as an inferior source of protein.

Well… Not completely true. 

In fact, meat meals can have quite a lot of proteins and some added minerals. The exact percentage depends on the source of tissues.

It is true that the AAFCO definition leaves some things open (more on this later). But a good meat and bone meal can be a great source of protein and minerals, in addition to whole meats.

Whole Wheat

Should dogs eat grains? Yes, some researchers seem to think so.

Grains can provide a host of benefits: fiber, vitamins, minerals, great carbs, and energy. They even bring in some protein.

Whole wheat is a whole grain and is considered a good choice for dog food.

Still, some dog owners worry about the glyphosate present in most of the wheat today, whether it is whole or refined.

There are many conflicting studies about the adverse effects of glyphosate on humans and animals. So it might be good to consult a vet on this one.

Additionally, if your dog is allergic to wheat and gluten, it’s best to avoid this ingredient.

Pea Protein

For dogs with grain allergies, grain-free dog food can be a great choice.

But, in 2018, FDA issued a report and started an investigation into the potential link between grain-free foods and dilated cardiomyopathy (DCM) in dogs.

The most recent study on the topic highlights the potential link between pea protein, often used in grain-free foods, and DCM.

The research is still ongoing. So, for the time being, if your dog is more prone to heart disease, it might be best to choose a dog food with fewer peas and their derivatives.


Soy provides one of the most complete proteins of all the plants. It has 9 amino acids and can be a good addition to dog food.

However, soy is also an allergen. Some dogs can only eat it in the form of protein.

Soy allergy is not that common among dogs. In fact, most dogs are often allergic to beef and chicken.

But if you suspect your dog is allergic to soy products, it might be best to take them to a vet for an allergy test and avoid soy.

Brewers Rice / Wheat Middlings

Both of these ingredients are often seen on dog food labels, though usually further down the ingredient list.

Brewers rice is simply a collection of small pieces of white rice that didn’t make it into human food.

Wheat middlings is a by-product of wheat flour milling. 

Both of these are considered inferior grains. But, for that to be true, white rice and wheat flour themselves would have to be inferior.

The truth is that both brewers’ rice and wheat middlings add specific nutrients to dog food. This is especially true for fiber, carbs, and certain vitamins, especially B-vitamins.

You don’t want them to be among the first ingredients, though, because there are better options. But the ingredients themselves help round up the nutritional value of the food.

Farmed Salmon

Another common ingredient in dog food is salmon. Though most pet food manufacturers do not specify whether they are using a wild-caught or farmed salmon, you could reach out and ask.

Why? Because wild salmon has a lot of nutritional edge over the farmed one. It’s also the more expensive variant.

According to Cleveland Clinic, wild salmon is much less likely to have serious pollutants. It’s also not treated with antibiotics.

Furthermore, wild salmon offers more nutritional value and contains fewer calories.

If you’re worried about cancer-causing chemicals, opt for menhaden fish instead. Menhaden inhabits mid-level of the ocean and is less exposed to pollutants than other fish.

Natural Flavor

One would think that something as inconspicuous as “natural flavor” surely can’t be harmful.

Have you ever seen this ingredient on pet food labels? You probably thought it’s good that it was there. After all, isn’t natural what we want?

Well, yes. And no.

The main problem is the wide definition of what is considered a natural flavor.

FDA defines natural flavor in the following way:

natural flavor fda
Source: FDA

Many things could be lurking behind this innocent-looking ingredient. For example, protein hydrolysate, which we already mentioned at the beginning of this article in relation to MSG.

Or fruit juice, which would up the sugar intake.

So, if you come across dog food with “natural flavor,” it might be good to contact the manufacturer first and ask exactly what is meant by this.

Unspecified Ingredients

Save the best for last, right? This is where it gets pretty interesting (and potentially confusing).

Pet food labels sometimes include ingredients that aren’t very forthcoming. What do we mean by this?

Take a look at the following dog food ingredients:

  • Animal digest
  • Animal fat
  • Poultry fat
  • Bone meal
  • Meat meal
  • Meat by-products
  • Fish oil
  • Fish meal
  • Vegetable oil

To make matters worse, some of the definitions provided by AAFCO for these ingredients can be confusing from time to time.

So, the problem is twofold:

  • The source of an ingredient (meat, fat, by-products, etc.) is unknown — so no nutritional value can be ascertained, nor potential allergy prevented
  • Even with the source relatively known, sometimes it can contain many varying parts (by-products and meals)

Hopefully, in the future, we will have clearer definitions and a mandatory specification of the ingredients used.

In the meantime, inform yourself of the manufacturers’ recall history, feeding trials, and food safety standards.

What Are GRAS & FSMA?

“Generally recognized as safe” (GRAS) is an FDA designation — meaning that a chemical or substance is recognized as safe for use in the food industry.

The ingredients with GRAS designation do not need to go through safety testing as prescribed by FSMA.

The Food Safety Modernization Act (FSMA) is a law passed in 2011 in response to many food problems in the US and abroad.

Its focus is on preventive measures rather than reactive ones, such as product recall after contamination occurs.

The law addresses issues related to food safety. It also gave FDA greater power and more jurisdiction in terms of food regulation.

However, it must be noted that the GRAS designation applies only to food products. These chemicals or substances can still have other non-food uses, which may pose other health risks. The FDA database, affirmed GRAS database, and notice database contain a list of all the current and pending GRAS substances.

In terms of pet food, FDA regulates all animal feeds, both domestic and imported. Many states, however, also utilize AAFCO guidelines.


When researching dog food ingredients, it’s always a good idea to browse through the FDA database of recalls. The database is freely available to everyone.

This way, you will get more insight about a pet food manufacturer, which products were recalled, and why. You will also learn whether the recalls were voluntary or mandated.

You can access the FDA recalls database to see all the recalls from 2006 onwards.

The Bottom Line

There are many questionable ingredients still circulating in pet food today.

For some of these ingredients, science is just catching up about their adverse effects on pet health.

While the institutions do their best to prevent and minimize the hazards, sometimes it’s hard to discern what the real information is.

Ultimately, it’s vital to gather all the available information and make an informed decision.

This way, you are ensuring the health and wellbeing of your pets.

Be on the lookout for new information regarding the ingredients mentioned in this article. Many of them are still a hot topic, and it might take some time until we know for sure whether to use them or not.

In the meantime, it might be a good idea to limit — or completely avoid some of these ingredients.

Kristin Hitchcock
Kristin has been writing about dogs and their nutrition for the last four years. She enjoys educating pet parents on the best things to feed their beloved furry friends using the latest scientific research.

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