Dog Supplement Ingredients to Avoid: What's Really in Your Dog's Chews?

Last Updated: February 2026 · Reviewed by Vets Verified

Walk into any pet store and you'll find an entire aisle of soft, chewy dog supplements that look and smell like treats. Colorful packaging, bold claims, and happy dogs on the label. But flip the bag over and read the ingredient list — really read it — and you'll find something most brands don't want you to notice.

The therapeutic ingredients you're paying for? They're often buried beneath a long list of fillers, binders, and artificial additives that are there for one reason: to hold a chew together and make your dog willing to eat it.

This guide breaks down the most common dog supplement ingredients to avoid, explains what they do (and don't do), and shows you what a clean-label supplement actually looks like.

Why the Format of a Supplement Matters More Than You Think

Before we get to specific ingredients, it's worth understanding why soft chews inherently require fillers while powders generally don't.

A soft chew is, at its core, a food product. To create a chew that holds its shape, stays shelf-stable, tastes good to dogs, and doesn't crumble in the bag, manufacturers need:

• Binders — to hold everything together (glycerin, rice flour, maltodextrin)
• Preservatives — to prevent mold and extend shelf life (mixed tocopherols, rosemary extract, or synthetic options)
• Palatants — to make your dog actually eat it (artificial chicken flavor, liver flavor, natural flavors)
• Fillers — to create the chew's texture and body (brewer's dried yeast, dried peas, oat flour)

None of those add any health benefit. They're manufacturing necessities. And they take up significant space in the supplement's formula — space that could otherwise go to active, therapeutic ingredients.

Powder-based supplements skip most of this. The active ingredients are the formula. There's no chew to bind, no texture to maintain, and no palatability tricks needed — the powder is mixed into food.

The 7 Dog Supplement Ingredients to Avoid (or Question)

1. Maltodextrin

What it is: A processed carbohydrate derived from corn, wheat, or rice starch. It's used as a filler and binder in soft chews.

Why it's a red flag: Maltodextrin has a high glycemic index — higher than table sugar — meaning it causes a rapid spike in blood glucose. For dogs with diabetes, insulin resistance, or weight management challenges, this is particularly problematic. It also feeds harmful gut bacteria, which is ironic in a probiotic supplement.

The bigger issue: Maltodextrin is often listed near the top of ingredient lists in "probiotic" chews, meaning it's present in significant quantities. You're paying for gut health support, and the filler is actively undermining it.

Red flag brands: Several major soft chew probiotics list maltodextrin in their first 5 ingredients.

2. Artificial Chicken Flavor / "Natural Flavors"

What it is: A palatability additive used to make the chew taste appealing to dogs. "Natural flavors" is a catch-all term that can include a wide range of animal or plant-derived flavor compounds.

Why it's a red flag: The term "natural flavors" is almost meaningless on a pet supplement label. It could be a concentrated spray of animal digest (rendered chicken parts, primarily), or it could be a synthetic-adjacent compound that qualifies as "natural" under loose industry definitions. You simply don't know what's in it.

More importantly, dogs with food sensitivities or allergies may react to hidden protein sources in "natural flavors" — without the owner ever connecting the dots.

3. Glycerin (Vegetable Glycerin)

What it is: A thick, syrupy liquid used to keep soft chews moist and prevent them from hardening. It's a byproduct of biodiesel production or soap manufacturing.

Why it's a concern: Glycerin isn't toxic to dogs, but it's a sugar alcohol that contributes to caloric density without nutritional benefit. High amounts can cause digestive upset in some dogs. Its primary purpose is to give the chew a soft, moist texture — which is entirely for palatability and shelf appeal, not your dog's health.

4. Brewer's Dried Yeast (as a filler)

What it is: A common bulking agent in dog supplements and treats. It's a byproduct of the brewing industry.

Why it's nuanced: Brewer's yeast isn't inherently bad — it contains B vitamins and trace minerals. But when listed as a primary ingredient in a probiotic supplement, it's functioning primarily as a flavor enhancer and filler, not as a meaningful nutritional contribution. Dogs can also develop yeast sensitivities, which is particularly problematic in a supplement meant to support gut balance.

Watch for brewer's dried yeast appearing before or alongside the active probiotic strains in the ingredient list — that's a sign the formula is filler-heavy.

5. Oat Flour / Rice Flour / Pea Flour

What it is: Carbohydrate flours used as binders and bulking agents to give soft chews their doughy, holdable texture.

Why it's a concern: These are pure binder ingredients. They dilute the active ingredient concentration. For dogs with grain sensitivities or those on low-carbohydrate diets, flour-based binders can trigger digestive issues. And for dogs with inflammatory conditions, additional carbohydrate load is the last thing they need from a supplement intended to reduce inflammation.

6. Titanium Dioxide / Artificial Colors

What it is: Artificial colorants used to make supplements look more visually appealing (to you, the buyer — dogs don't care about color).

Why it's a red flag: Titanium dioxide is classified as a possible carcinogen in some countries' food safety frameworks. While research in dogs is limited, there's no therapeutic rationale for a supplement to contain colorants. If your dog's supplement contains artificial colors, ask yourself: who is that ingredient for?

7. Sucrose / Cane Molasses / Honey

What it is: Added sugars used to improve palatability.

Why it's a problem: Sugar feeds harmful gut bacteria and yeast. In a probiotic supplement — a product explicitly designed to improve gut bacterial balance — added sugars directly undermine the goal. Sucrose and cane molasses are particularly problematic for dogs with yeast overgrowth, which often manifests as chronic ear infections, paw licking, or skin irritation.

What a Clean Supplement Label Actually Looks Like

A clean-label dog supplement should have:

The Powder vs. Chew Difference: Active Ingredient Density

Here's a practical illustration. A typical soft chew dog probiotic weighing 4–5 grams might contain:

• ~2.5–3g of fillers, binders, and flavoring agents
• ~0.5–1g of actual active ingredients (probiotics, enzymes, vitamins)
• ~0.5g of moisture content

That means 50–60% or more of what your dog consumes is filler.

A powder sachet of the same weight can be almost entirely active ingredients — no binders needed, no moisture-retention agents, no texture creation. The powder mixes directly into food, and your dog absorbs it through normal digestion.

This is why powder-based supplements like Plentum can pack a Canine Oral Health Postbiotic (COHP), prebiotics, probiotics, colostrum, L-Glutamine, and joint support into a single daily sachet without the formula being diluted by chew-manufacturing requirements.

How to Read a Dog Supplement Label in 60 Seconds

Follow this quick checklist when evaluating any dog supplement:

Step 1: Find the Guaranteed Analysis. This tells you the minimum levels of active ingredients. Compare across brands on a per-serving basis, not per-package.

Step 2: Read the first 5 ingredients. In a proper supplement, these should be the therapeutic ingredients — probiotic strains, specific enzymes, named botanical extracts. If you see maltodextrin, oat flour, or glycerin in the top 5, the formula is filler-heavy.

Step 3: Check for specific probiotic strain names. "Probiotic blend (2 billion CFU)" tells you almost nothing. A quality supplement names specific strains: Lactobacillus acidophilus, Bifidobacterium animalis, Bacillus coagulans. These have actual clinical research behind them.

Step 4: Look for third-party quality certifications. NASC (National Animal Supplement Council) membership with their quality seal, cGMP certification, and NSF or USP testing are the gold standards. These mean independent auditors have verified label accuracy and manufacturing quality.

Step 5: Google any clinical claims. "Clinically tested" means nothing without a citation. A legitimate clinical study will have a PubMed or PMC reference number. For example, Plentum's COHP is backed by a peer-reviewed randomized controlled trial (PMC12153626), showing a 44% reduction in bad-breath bacteria markers.

The Bottom Line: Your Dog Deserves Better Than Filler

Soft chews dominate the dog supplement market because they're easy to sell. Dogs like treats. Owners feel good about giving treats. Brands can price them at a premium while using cheap filler ingredients to keep manufacturing costs low.

But your dog doesn't need a treat — they need therapeutic nutrition. And therapeutic nutrition requires active ingredient density, clinical validation, and honest labeling.

Before you buy any dog supplement, take two minutes to read the ingredient list. Know the red flags. And ask the hard question: am I paying for filler, or am I paying for results?

References

• National Animal Supplement Council (NASC). Quality Seal Program Guidelines. nasc.cc
• Case LP, et al. Canine and Feline Nutrition, 3rd ed. Mosby Elsevier, 2011.
• Swanson KS, et al. "Gut microbiome of dogs and cats." Journal of Animal Science, 2020.
• PMC12153626: Randomized controlled trial on COHP and volatile sulfur compound reduction in dogs.
• FDA Center for Veterinary Medicine. Animal Feed Safety. fda.gov/animal-veterinary

Support your dog's health with Advanced K9 Microbiome Care — the postbiotic supplement trusted by 5,185+ dog parents. One sachet a day.

Plentum supplements are not intended to diagnose, treat, cure, or prevent any disease. Consult your veterinarian before starting any new supplement regimen.

Related reading: What Can Dogs Eat? Complete Guide