Supplements For Dogs: Hidden Ingredients To Avoid

supplements for dogs

Are your dog’s supplements free of harmful ingredients? In most cases, your answer should be no.

While the manufacturer will name the Active Ingredients in their dog supplements on the label … they don’t always disclose the Inactive Ingredients.

So I’m going to help you decipher what hidden ingredients might be in supplements for dogs. But first, here’s why it’s important that you know about the hidden ingredients (even if you’re buying natural products) …

Regulation Of Supplements For Dogs

You might think the supplements you buy for your dog are tightly regulated. But this isn’t the case. There are a few rules, but most dog supplements don’t go through any approval process.

  • AAFCO (American Association Of Feed Control Officials) only allows ingredients that are approved as a pet food ingredient. That means manufacturers can’t include something like milk thistle or dandelion in a product if they want AAFCO approval.
  • The FDA (US Food and Drug Administration) lists ingredients that are “generally recognized as safe” (GRAS) – but animal supplements aren’t included under their DSHEA (Dietary Supplement Health and Education Act), so GRAS doesn’t mean it’s safe for your dog.

In a nutshell, this means it’s your job to make sure there aren’t any nasty ingredients in your dog’s supplements … because nobody’s doing it for you. Let’s talk about those hidden, inactive ingredients, then I’ll tell you how to avoid them.

What Are Excipients?

Excipients are chemicals added to your dog’s supplements. Many are toxic and foreign to your dog’s body. with unpredictable health risks. Excipients include things like:

  • Fillers
  • Binders
  • Disintegrates
  • Lubricants
  • Sweeteners
  • Flavorings
  • Coloring Agents
  • Coating Agents
  • Preservatives
  • Emulsifiers
  • Detergents
  • Gums and Resins
  • Surfactants
  • Bulking Agents
  • Dispersing and Suspending agents
  • Oxidants

Here are some more excipients you’ll find in many supplements:

Food Based Excipients

Some manufacturers will use food-based excipients in their products. These include things like:

  • Cellulose: cellulose is used as a filler in both pet foods and supplements (and also in products for humans like packaged grated cheese). Cellulose is sawdust … literally! Dogs don’t have cellulase, the enzyme required to break down cellulose and metabolize it, so it’s quite indigestible for them.
  • Rice powders: these are often genetically engineered, so avoid supplements with rice powders unless they’re organic.

Next, let’s categorize these excipients so you can find them on the label. Or you can call the manufacturer to see if any of these inactive ingredients are in your dog’s supplements.

Harmful Excipients To Avoid

Here are 9 hidden excipient categories that are in a lot of supplements.


Fillers are used to increase the volume of material. Common non-food fillers are talc (a known carcinogen) and silicon. Food grade fillers include:

  • Cornstarch
  • Lactose
  • Cellulose
  • Sorbitol
  • Calcium phosphate

Just because fillers are food grade doesn’t mean you want them in your supplements. When you compare one supplement to another, you may think one is better value. But then you look at the recommended dosage and see you need to give more of the lower cost product. That’s probably because it contains fillers. You get what you pay for.


Binders are used in tablets to bind the components together and make the tablets harder. Binders include:

  • Lecithin
  • Honey
  • Sorbitol
  • Gum Arabic
  • Cellulose (again, cellulose is sawdust)

These food grade ingredients may not all be harmful. But when you buy tablets you’re paying for something your dog doesn’t need. And sugars can feed yeast and unhealthy bacteria in your dog’s gut.

RELATED: Read about gut health and leaky gut in dogs ..

Disintegration Aids

Disintegration aids help tablets swell and break apart so they can dissolve in the gastrointestinal tract. Examples include starches like potato and corn starch, confectioners sugars as well as:

  • Sodium carboxy-methylcellulose
  • Croscaramellose sodium
  • Sodium starch glycolate
  • Crosspovidone
  • Alginic acid

Many of these ingredients can cause allergies, rashes and asthma attacks. In humans they’ve been shown to contribute to plaque formation and hardening of the arteries.

Lubricants And Flow Agents

These ingredients help release the tablets from molds and dies used in manufacturing. You can see them on many supplement labels. They’re there to smooth the manufacturing process and increase the time tablets take to dissolve. They’re not there for any health reason.

While these are mainly of vegetable origin, those vegetables are often genetically modified foods like corn. You’ll also see:

  • Magnesium stearate (One study has linked magnesium stearate to immune system suppression)
  • Calcium stearate
  • Stearic acid
  • Polyethylene glycol
  • Vegetable stearate (Can cause indigestion)
  • Silica (Can cause indigestion)

Flavoring Agents And Sweeteners

Sweeteners are very commonly used in liquid, powdered and chewable products. These include:

These artificial flavoring sweeteners are completely unnecessary and can feed viruses, bacteria (bad ones like clostridia) and yeast.

Flavorings are common in chewable supplements to make them taste better. These include:

  • Beef or bacon flavoring. What does natural bacon flavor mean? It usually comes from pork belly fat, but it can come from virtually any rendered animal.
  • Often patented and completely synthetic
dog supplements ingredients

Coloring Agents

Color is added strictly for marketing purposes. It makes the product look more attractive (to you and certainly not your dog)!

  • Some are of vegetable origin, like beet, carrot or chlorophyll
  • But synthetics are more common and can lead directly 
to some cancers

Coating materials

Coatings are to …

  • Increase shelf life
  • Protect the product from moisture
  • Mask unpleasant odors and flavors
  • Make the product easier to swallow
  • Stop the tablet breaking apart too early

Pharmaceutical glaze, confectioners glaze, and natural glaze are shellacs, which are:

  • Difficult to digest
  • Made from petrochemicals that are known carcinogens

If these coatings are natural, they’re usually made from beetle wings, corn (likely GMO) or palm trees (which have a huge sustainability issue).


Preservatives used in supplements are almost always synthetic. They include:

  • Synthetic non-organic forms of sulfur or selenium
  • Synthetic vitamins like E and C

All chemical additives, preservatives and other inorganic or toxic chemicals are added for the benefit of the manufacturer … and not your dog!


Gums are used in many supplements as emulsifiers, to suspend insoluble drug powders and as a bulk forming laxative to relieve constipation (in human products). The most commonly used gums are:

  • Arabic (derivative of Acacia senegal)
  • Tragacanta
  • Karaya

These additives are used as an aphrodisiac in India! Arabic and tragacanta gums are used in antihistamine and corticosteroid drugs to calm allergic reactions like urticaria, asthma and pruritus … but ironically, these ingredients can cause allergic reactions!

Other Synthetic Additives

There’s a long list of other undesirable and often synthetic additives that are commonly used in supplements. These include:

  • Hydroxypropyl methylcellulose
  • Cellulose Starch
  • Croscarmellose sodium
  • Sodium starch glycolate
  • Silicon Dioxide
  • Hydroxyl cellulose
  • Red 40
  • Polyethylene glycol 3350
  • Magnesium stearate
  • Resins
  • Dicalcium phosphate
  • Polysorbate 80
  • Titanium dioxide
  • Povidone (PVP)
  • Gluten
  • Genetically Modified Organisms
  • Parabens
  • MSG
  • Tartrazine
  • Carrageenan

So there’s the laundry list of unwanted ingredients lurking in your dog’s supplements. You know what to avoid … but how do you actually find supplements without these harmful inactive ingredients if they’re not listed on the label?

Choosing A Safe And Natural Supplement For Your Dog

Just like whole food diets are best for your dog, the first rule of supplements is to always buy supplements that are sourced from whole foods. The synthetic vitamins and minerals in most supplements can inhibit the way the body absorbs nutrients. Cells have receptor sites that turn cellular functions on and off. These receptors can become “clogged” with lookalike vitamins or minerals. So when your dog first starts taking a synthetic supplement you may see some improvement. Bbut when the receptors become clogged with the inadequately functioning faux nutrients, they can’t function properly.

Powders (And Whole Foods) Are Best

Most powdered supplements are safer than tablets or capsules. Tableting, encapsulation, odor control, preservation and shelf life in tablets and capsules mean they have a number of excipients that are best to avoid. The best powders are produced at temperatures under 118°F and are considered raw. Buy organic supplements if you can.

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Let’s talk about some of the problems with capsules and tablets.


Capsules are made with animal or vegetable gelatin. Vegetable gelatin is made from a chemical biopolymer that comes from brown seaweed and it’s definitely preferable to animal gelatin. Animal gelatin comes from:

  • Tallow
  • Bone
  • Bone marrow
  • Animal tissue scraps including diseased
  • organs and tumors
  • Animals likely not well fed, containing
  • feed toxins and hormones (think of chickens fed
  • donuts and candy corn!)

You need to find out if the gelatin in your dog’s capsule is vegetable or animal. Never buy products that use animal gelatin. And remember, you get what you pay for, so beware cheap supplements and research the manufacturer’s reputation.


Tablets are worse than capsules for several reasons:

  • Coatings (even coatings from natural food sources) are bad. Believe it or not, most natural coatings are made from beetle wings and other bug parts!
  • Very high temperature processing, which depletes nutrients
  • Petroleum derived chemicals like ethyl cellulose (as a solvent) or the carcinogen methylene chloride (as a coating)
  • Synthetic dyes and flavorings like Red 40 and Yellow 5 – also carcinogens
  • Artificial sweeteners
  • BHA, BHT and TBHQ (chemical antioxidants used as coatings and dyes). These are known to cause behavioral problems in children. What about our pets? They’re almost certainly affected too.

Many of these ingredients in tablets can cause allergic reactions, fatigue, depression and insomnia in people … and it’s no different for pets.

Remember … these ingredients won’t be listed on the label so you must do your research! You’ll probably have to call the manufacturer to find out what’s really in the tablets. Most inactive ingredients aren’t good for your dog and some can even cause cancer.

Finally, even if you bought your supplements from a veterinarian (whether conventional or holistic), that doesn’t mean they’re safe or even effective. So do your own research into any product you give your dog.  Contact the manufacturer for a list of all ingredients and excipients and remember: you can often avoid excipients by choosing powders whenever you can.


Desai, PM et al. Review of Disintegrants and the Disintegration Phenomena. Journal of Pharmaceutical Sciences, 105 (2016) 2545e2555

Tebbey PW, Buttke TM. Molecular basis for the immunosuppressive action of stearic acid on T cells. Immunology. 1990 Jul;70(3):379-84. Erratum in: Immunology 1990 Oct;71(2):306. 

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