January 13, 2026

Fillers and Binders in Dog Supplements: What to Avoid

Q: What are fillers in dog supplements?

Fillers are inactive ingredients added to supplements to increase volume, improve manufacturing, or reduce costs. They include bulking agents (maltodextrin, rice flour, cellulose), binders (starch, gums), flow agents (magnesium stearate, silicon dioxide), and coatings. Some fillers serve legitimate manufacturing purposes (making tablets hold together), while others are just cheap bulk to make products look larger. Fillers provide no nutritional value and can dilute the concentration of active ingredients, meaning you're paying for inactive material instead of nutrients.

Q: Are fillers in dog supplements bad?

It depends on the filler and the amount. Some fillers are benign and necessary for manufacturing (small amounts of silicon dioxide prevent clumping). Others are problematic: maltodextrin spikes blood sugar, artificial colors provide no benefit and may cause reactions, and excessive fillers dilute active ingredients. The main issue is that fillers replace real nutrition—supplements with 50%+ filler content deliver less of what you're paying for. High-quality supplements minimize fillers and use whole-food ingredients instead of synthetic isolates padded with cheap bulk.

Q: What is maltodextrin in dog supplements?

Maltodextrin is a highly processed carbohydrate made from corn, rice, or potato starch. It's used as a cheap filler and bulking agent in supplements. Maltodextrin has a high glycemic index (spikes blood sugar quickly), provides no nutritional value, and is often GMO-derived. In powdered supplements, maltodextrin can make up 50-80% of the product weight—meaning most of what you're buying is cheap sugar filler, not active ingredients. Dogs don't need maltodextrin, and it's particularly problematic for overweight or diabetic dogs.

Q: Is magnesium stearate safe for dogs?

Magnesium stearate is generally considered safe in small amounts. It's a flow agent that prevents ingredients from sticking to manufacturing equipment during tablet/capsule production. However, some concerns exist: it may reduce nutrient absorption, can cause digestive upset in sensitive dogs, and is often derived from hydrogenated oils (cottonseed or palm oil). Small amounts (<1-2% of formula) are acceptable and sometimes necessary for manufacturing, but high-quality supplements minimize or avoid it by using whole-food ingredients that don't require flow agents.

Q: Why do dog supplements have so many fillers?

Manufacturers use fillers for three main reasons: (1) Cost reduction—fillers like maltodextrin and rice flour are cheaper than active ingredients, allowing higher profit margins. (2) Manufacturing ease—flow agents and binders help tablets/capsules form consistently and prevent machinery clogging. (3) Volume creation—fillers make products look larger and more substantial, even when active ingredients are minimal. Budget supplements often contain 50-70% fillers to cut costs. Premium supplements minimize fillers by using concentrated whole-food ingredients that naturally bind and flow well.

Q: What are the worst fillers in dog supplements?

The most problematic fillers are: (1) Maltodextrin—high glycemic index, no nutrition, often 50%+ of product. (2) Artificial colors (FD&C dyes)—purely cosmetic, potential allergens. (3) Excessive rice flour/starch—cheap bulk with minimal nutrition. (4) Propylene glycol—used in soft chews, potential toxicity concerns. (5) BHA/BHT preservatives—synthetic antioxidants with health concerns. (6) Titanium dioxide—whitening agent, unnecessary and questioned for safety. Look for supplements that list fillers low on the ingredient list or avoid them entirely with whole-food formulations.

Q: How can you tell if a dog supplement has too many fillers?

Check the ingredient list: (1) If maltodextrin, rice flour, or starch appears in the first 5 ingredients, fillers dominate. (2) If the label lists 15+ ingredients but serving sizes are tiny (1-2 grams), it's mostly filler. (3) If 'active' ingredients have tiny amounts (50mg in a 2000mg serving), the rest is filler. (4) If the powder is pure white and flows like sugar, it's likely maltodextrin-heavy. (5) Compare price per active ingredient—cheap supplements use fillers to appear affordable. Quality supplements have short ingredient lists with whole foods or concentrated extracts, not long lists of inactive additives.

Q: Are natural fillers better than synthetic fillers?

Natural fillers are generally better, but the best option is minimal fillers period. Natural fillers like rice flour, tapioca starch, or cellulose are less concerning than synthetic ones like maltodextrin or propylene glycol—they're less processed and less likely to cause reactions. However, they still dilute active ingredients and add no nutritional value. The optimal approach is whole-food formulations where ingredients naturally bind without requiring separate fillers. For example, air-dried organ meat holds together naturally without needing binders, flow agents, or bulking agents.

Q: What should I look for in a clean dog supplement?

A clean supplement has: (1) Short ingredient list—only active ingredients and minimal processing aids. (2) Whole-food sources—beef liver, fish, kelp instead of synthetic isolates. (3) No maltodextrin, artificial colors, or excessive starches. (4) Transparent sourcing—specifies where ingredients come from. (5) High concentration of actives—serving size reflects real food, not filler bulk. (6) Minimal processing—freeze-dried or air-dried instead of high-heat rendered. (7) Third-party testing for purity. Look for supplements where you recognize every ingredient as actual food, not chemical additives.

Q: Can fillers cause allergies or sensitivities in dogs?

Yes, some fillers can trigger reactions in sensitive dogs. Common culprits include: (1) Corn-derived maltodextrin (dogs with corn sensitivities). (2) Soy lecithin (dogs with soy allergies). (3) Wheat or rice flour (grain sensitivities). (4) Artificial colors (potential allergens and behavioral reactions). (5) Preservatives like BHA/BHT (digestive upset or skin reactions). (6) Gums and starches (digestive issues in some dogs). If your dog has food sensitivities, choose supplements with minimal ingredients and avoid common allergen fillers. Whole-food supplements without fillers reduce reaction risk.

Pick up a popular dog supplement and check the ingredient list. Chances are, the first few ingredients aren't vitamins or minerals—they're fillers like maltodextrin, rice flour, or cellulose. These inactive ingredients don't support your dog's health. So why are they there, and should you avoid them?

⚠️ Common Fillers and Binders: Quick Reference

Ingredient	Purpose	Concern Level
Maltodextrin	Cheap bulking filler	High - Avoid
Artificial colors	Cosmetic only	High - Unnecessary
Propylene glycol	Moisture retention	High - Toxic concerns
Rice flour/starch	Bulking, binding	Moderate - Check amount
Magnesium stearate	Flow agent	Moderate - OK in small amounts
Silicon dioxide	Anti-caking	Low - Generally safe
Cellulose	Bulking, binding	Low - Inert fiber

Best option: Supplements with no fillers—just whole-food ingredients that naturally bind

This guide explains what fillers and binders are, why manufacturers use them, which ones to avoid, and how to find clean supplements for your dog.

What Are Fillers, Binders, and Flow Agents?

Supplements contain two types of ingredients: active ingredients (vitamins, minerals, nutrients that benefit health) and inactive ingredients (fillers, binders, and flow agents that serve manufacturing purposes).

Fillers (Bulking Agents):

Fillers add volume to make products look larger without increasing active ingredients. Common examples:

Maltodextrin — Highly processed carbohydrate from corn/rice/potato starch
Rice flour — Finely ground rice used as cheap bulk
Dextrose — Simple sugar filler
Cellulose — Plant fiber with no nutritional value

Fillers are the worst offenders because they dilute active ingredients. A supplement that's 60% maltodextrin means you're paying for 60% sugar filler instead of nutrients.

Binders:

Binders hold tablets and capsules together so they don't crumble. Common binders:

Starch (potato, tapioca, corn)
Gums (guar gum, xanthan gum, acacia gum)
Gelatin (animal-derived, acceptable binder)

Small amounts of binders are sometimes necessary for tablet manufacturing. The question is whether they're minimized or excessive.

Flow Agents (Anti-Caking Agents):

Flow agents prevent ingredients from clumping and help them move smoothly through manufacturing equipment. Common examples:

Magnesium stearate — Most common flow agent
Silicon dioxide — Prevents clumping in powders
Stearic acid — Similar to magnesium stearate

Flow agents are used in tiny amounts (usually <2% of formula) and are less concerning than fillers, though some manufacturers avoid them entirely.

The Worst Fillers in Dog Supplements

Not all fillers are equally problematic. Here are the ones to avoid:

1. Maltodextrin: The Biggest Offender

Maltodextrin is a highly processed carbohydrate made by breaking down corn, rice, or potato starch with enzymes and acids. It's used as a cheap filler because it's:

Inexpensive — Costs a fraction of real nutrients
White and powdery — Makes products look "clean" and professional
Easy to work with — Blends smoothly and doesn't clump

Why Maltodextrin Is Problematic:

High glycemic index — Spikes blood sugar quickly (GI of 105-130, higher than table sugar)
No nutritional value — Pure empty calories
Often GMO — Usually derived from GMO corn
Can dominate formulas — Many supplements are 50-80% maltodextrin by weight

Example: A popular powdered multivitamin for dogs lists maltodextrin as the #1 ingredient. The 2,000mg serving contains maybe 200-300mg of active vitamins and minerals—the rest is maltodextrin. You're paying for 85% cheap filler.

Maltodextrin is particularly concerning for overweight or diabetic dogs. It provides no benefit and actively harms metabolic health.

2. Artificial Colors (FD&C Dyes)

Artificial colors like Red 40, Yellow 5, Blue 1 serve one purpose: making products visually appealing to humans. Dogs don't care what color their supplements are.

Why they're problematic:

Zero benefit — Purely cosmetic
Potential allergens — Can cause reactions in sensitive dogs
Behavioral concerns — Some studies link artificial dyes to hyperactivity (more research in humans than dogs, but concerning)

If a supplement contains artificial colors, it signals the manufacturer prioritizes appearance over health.

3. Propylene Glycol

Propylene glycol is used in soft chews and semi-moist treats to retain moisture and prevent hardening.

The problem:

Toxic to cats — Causes Heinz body anemia
Questionable safety for dogs — Generally recognized as safe (GRAS) in small amounts, but unnecessary
No nutritional value — Just a moisture-retaining agent

While propylene glycol won't kill dogs in the amounts used in treats, there's no reason to include it when safer alternatives exist.

4. BHA and BHT (Synthetic Preservatives)

BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene) are synthetic antioxidants used to prevent fat oxidation and extend shelf life.

Concerns:

Potential carcinogens — Some animal studies link BHA to cancer
Unnecessary — Natural preservatives (vitamin E/tocopherols, vitamin C) work well
Digestive issues — Can cause upset stomach in sensitive dogs

Many manufacturers have phased out BHA/BHT in favor of natural alternatives.

5. Titanium Dioxide

Titanium dioxide is a whitening agent used to make tablets and powders look brighter and more uniform.

Why avoid it:

Purely cosmetic — No functional benefit
Safety questions — Banned in Europe as a food additive (2022), though still allowed in US
Potential inflammatory — Some research suggests it may cause gut inflammation

Fillers That Are Less Concerning (But Still Not Ideal)

Some fillers are problematic mainly because they dilute active ingredients, not because they're harmful:

Rice Flour and Starches

Rice flour, potato starch, and tapioca starch are natural fillers used for bulking and binding.

The issue: They're not harmful, but they're nutritionally empty. A supplement that's 40% rice flour means 40% of what you're buying provides zero benefit.

When they're acceptable: Small amounts (<10% of formula) for binding tablets are fine. Large amounts as primary fillers are not.

Cellulose (Plant Fiber)

Cellulose is insoluble fiber derived from plant cell walls. It's used as a bulking agent and binder.

The reality: Cellulose passes through dogs undigested—it's inert. It's not harmful but provides no nutrition. Excessive cellulose means you're paying for wood pulp instead of active ingredients.

Gums (Guar Gum, Xanthan Gum)

Gums are used to bind and thicken. In small amounts, they're generally safe.

Potential issue: Some dogs experience digestive upset (gas, loose stools) from gums. If your dog is sensitive, avoid supplements with multiple gums listed.

Flow Agents: Necessary or Avoidable?

Flow agents like magnesium stearate and silicon dioxide are used in tiny amounts (usually 1-2% of formula) to help manufacturing.

Magnesium Stearate

Magnesium stearate prevents ingredients from sticking to machinery during tablet production.

The debate:

Pro: Used in minuscule amounts, generally recognized as safe, and sometimes necessary for consistent tablet production
Con: May reduce nutrient absorption, often derived from hydrogenated oils (cottonseed or palm), and can cause digestive upset in sensitive dogs

Conclusion: Magnesium stearate in small amounts (<1-2%) is acceptable if needed for manufacturing. High-quality supplements minimize it or avoid it by using whole-food ingredients that naturally bind.

Silicon Dioxide

Silicon dioxide (silica) prevents clumping in powdered supplements.

Safety: Generally considered safe in the tiny amounts used (<1%). It's inert and passes through the digestive system without being absorbed.

When it's a problem: If silicon dioxide appears high on the ingredient list (top 5), it indicates excessive use.

Why Do Manufacturers Use So Many Fillers?

If fillers provide no benefit, why are they so common? Three reasons:

1. Cost Cutting

Fillers are far cheaper than active ingredients. A supplement company can:

Buy $5 worth of vitamins and minerals
Mix with $1 worth of maltodextrin and rice flour
Sell the resulting 100 tablets for $30

The fillers make the product look substantial and allow higher profit margins.

2. Manufacturing Convenience

Tablets and capsules require consistent flow through machinery. Fillers and flow agents help materials move smoothly, preventing clumping and uneven distribution.

This is a legitimate reason—some processing aids are necessary for large-scale manufacturing. The question is whether manufacturers minimize them or abuse them.

3. Perception Management

Consumers perceive larger products as more valuable. A 2,000mg tablet looks more substantial than a 300mg tablet—even if the 2,000mg tablet is 85% filler.

Manufacturers use fillers to create bulk that doesn't deliver nutrition, but consumers don't read labels carefully enough to notice.

How to Identify High-Filler Supplements

Here's how to spot supplements loaded with fillers:

1. Check the Ingredient List Order

Ingredients are listed by weight, descending. If fillers appear in the first 5 ingredients, they dominate the formula.

Red flag examples:

"Maltodextrin, rice flour, dicalcium phosphate, magnesium stearate, vitamin C..."
"Cellulose, starch, silicon dioxide, beef liver powder..."

Better examples:

"Beef liver, beef kidney, beef heart..." (whole foods first, minimal additives)
"Fish oil, vitamin E..." (concentrated actives, short list)

2. Compare Serving Size to Active Ingredients

If a 2,000mg serving contains only 200mg of listed active ingredients, the remaining 1,800mg is filler.

Example of high-filler supplement:

Serving size: 2,000mg
Vitamin C: 50mg
Vitamin E: 30mg
Glucosamine: 100mg
Total actives: 180mg
Filler percentage: 91%

3. Look for Pure White or Brightly Colored Powders

If a powdered supplement is pure white and flows like sugar, it's likely maltodextrin-heavy. Whole-food supplements are usually tan, brown, or greenish because real food has color.

4. Check for Long Lists of Tiny Amounts

Supplements that list 25+ ingredients but have small serving sizes (1-2 grams) are using "pixie dust" amounts of actives padded with fillers.

Example: A supplement listing 30 herbs, vitamins, and minerals at 0.5mg each in a 2,000mg serving means 985mg (49%) is filler.

What Clean Supplements Look Like

High-quality supplements with minimal fillers share these characteristics:

1. Short Ingredient Lists

Clean supplements list only active ingredients and minimal processing aids (if any).

Example: "Grass-fed beef liver, beef kidney, beef heart, gelatin capsule" — That's it. Four ingredients, three of which are whole foods.

2. Whole-Food Sources

Whole foods naturally contain vitamins, minerals, and co-factors in their most bioavailable forms—no need for synthetic isolates padded with fillers.

Examples of whole-food supplements:

Freeze-dried organ meats (liver, kidney, heart)
Whole fish (sardines, anchovies)
Green-lipped mussel
Bone broth powder (real dehydrated broth, not flavor powder)

Learn more about why whole-food nutrients are superior to synthetic isolates.

3. Transparent Sourcing

Quality brands clearly state where ingredients come from:

"Grass-fed New Zealand beef liver"
"Wild-caught Alaskan salmon"
"Organic kelp from Iceland"

Vague labels like "fish oil" or "liver powder" without sourcing details are red flags.

4. High Concentration of Actives

Clean supplements have high ratios of active ingredients to total weight. A 500mg capsule of freeze-dried beef liver is 500mg of actual liver—100% active.

5. No Artificial Additives

No artificial colors, flavors, sweeteners, or synthetic preservatives. If preservation is needed, natural vitamin E (tocopherols) is used.

Are Natural Fillers Better Than Synthetic?

Natural fillers (rice flour, tapioca starch, cellulose) are less concerning than synthetic ones (maltodextrin, propylene glycol, artificial colors), but they're still fillers—they dilute active ingredients without providing nutrition.

The hierarchy:

Best: No fillers—whole-food ingredients that naturally bind (freeze-dried organs, whole fish)
Acceptable: Minimal natural fillers for manufacturing (small amounts of rice flour or starch for binding tablets)
Problematic: Excessive natural fillers that dominate formulas (40%+ rice flour just for bulk)
Worst: Synthetic fillers with no redeeming qualities (maltodextrin, artificial colors, propylene glycol)

The Watts Approach: Zero Fillers, Just Real Food

At Watts, we don't use fillers, binders, or flow agents. Our ingredient list is simple:

Grass-fed beef liver
Grass-fed beef kidney
Grass-fed beef heart

That's it. No maltodextrin, no rice flour, no magnesium stearate. Just whole-food organs that naturally provide vitamins, minerals, and co-factors in their most bioavailable forms.

Why we can skip fillers:

Air-drying preserves nutrients — No high-heat processing that requires synthetic fortification
Whole foods bind naturally — Organ meats hold together without needing binders
Small-batch production — No need for flow agents to run massive machinery
Transparent pricing — You pay for actual nutrition, not cheap bulk

Every gram of Watts is active nutrition. No filler, no fluff.

The Bottom Line: How to Avoid Fillers

When choosing dog supplements:

✅ Do:

Read ingredient lists carefully — Check what comes first
Calculate filler percentage — Compare serving size to active ingredient totals
Prioritize whole-food supplements — Freeze-dried organs, whole fish, green-lipped mussel
Look for short ingredient lists — 3-5 ingredients is ideal
Check for transparent sourcing — Where ingredients come from matters

❌ Avoid:

Maltodextrin in the first 5 ingredients — Indicates filler-heavy formula
Artificial colors — Purely cosmetic, no benefit
Propylene glycol — Unnecessary chemical additive
Long lists of trace ingredients — "Pixie dusting" with fillers
Pure white powders — Likely maltodextrin-dominated

The best supplements don't need fillers because they use concentrated, whole-food ingredients that deliver real nutrition in small doses. If you're buying supplements with 70% filler content, you're wasting money on inactive bulk instead of supporting your dog's health.

For more on how to evaluate supplement quality, see How to Read Dog Supplement Labels.

How to Read Dog Supplement Labels

Understanding ingredient quality and sourcing transparency

Whole Food vs. Synthetic Nutrients

Why bioavailability matters more than ingredient lists

What is Meat Meal in Dog Food?

Understanding processed proteins and manufacturing additives

Do Joint Supplements Actually Work?

Evidence-based guide to supplements that work vs filler-heavy formulas

Frequently Asked Questions

What are fillers in dog supplements?

Fillers are inactive ingredients added to supplements to increase volume, improve manufacturing, or reduce costs. They include bulking agents (maltodextrin, rice flour, cellulose), binders (starch, gums), flow agents (magnesium stearate, silicon dioxide), and coatings. Some fillers serve legitimate manufacturing purposes (making tablets hold together), while others are just cheap bulk to make products look larger. Fillers provide no nutritional value and can dilute the concentration of active ingredients, meaning you're paying for inactive material instead of nutrients.

Are fillers in dog supplements bad?

It depends on the filler and the amount. Some fillers are benign and necessary for manufacturing (small amounts of silicon dioxide prevent clumping). Others are problematic: maltodextrin spikes blood sugar, artificial colors provide no benefit and may cause reactions, and excessive fillers dilute active ingredients. The main issue is that fillers replace real nutrition—supplements with 50%+ filler content deliver less of what you're paying for. High-quality supplements minimize fillers and use whole-food ingredients instead of synthetic isolates padded with cheap bulk.

What is maltodextrin in dog supplements?

Maltodextrin is a highly processed carbohydrate made from corn, rice, or potato starch. It's used as a cheap filler and bulking agent in supplements. Maltodextrin has a high glycemic index (spikes blood sugar quickly), provides no nutritional value, and is often GMO-derived. In powdered supplements, maltodextrin can make up 50-80% of the product weight—meaning most of what you're buying is cheap sugar filler, not active ingredients. Dogs don't need maltodextrin, and it's particularly problematic for overweight or diabetic dogs.

Is magnesium stearate safe for dogs?

Magnesium stearate is generally considered safe in small amounts. It's a flow agent that prevents ingredients from sticking to manufacturing equipment during tablet/capsule production. However, some concerns exist: it may reduce nutrient absorption, can cause digestive upset in sensitive dogs, and is often derived from hydrogenated oils (cottonseed or palm oil). Small amounts (<1-2% of formula) are acceptable and sometimes necessary for manufacturing, but high-quality supplements minimize or avoid it by using whole-food ingredients that don't require flow agents.

Why do dog supplements have so many fillers?

Manufacturers use fillers for three main reasons: (1) Cost reduction—fillers like maltodextrin and rice flour are cheaper than active ingredients, allowing higher profit margins. (2) Manufacturing ease—flow agents and binders help tablets/capsules form consistently and prevent machinery clogging. (3) Volume creation—fillers make products look larger and more substantial, even when active ingredients are minimal. Budget supplements often contain 50-70% fillers to cut costs. Premium supplements minimize fillers by using concentrated whole-food ingredients that naturally bind and flow well.

What are the worst fillers in dog supplements?

The most problematic fillers are: (1) Maltodextrin—high glycemic index, no nutrition, often 50%+ of product. (2) Artificial colors (FD&C dyes)—purely cosmetic, potential allergens. (3) Excessive rice flour/starch—cheap bulk with minimal nutrition. (4) Propylene glycol—used in soft chews, potential toxicity concerns. (5) BHA/BHT preservatives—synthetic antioxidants with health concerns. (6) Titanium dioxide—whitening agent, unnecessary and questioned for safety. Look for supplements that list fillers low on the ingredient list or avoid them entirely with whole-food formulations.

How can you tell if a dog supplement has too many fillers?

Check the ingredient list: (1) If maltodextrin, rice flour, or starch appears in the first 5 ingredients, fillers dominate. (2) If the label lists 15+ ingredients but serving sizes are tiny (1-2 grams), it's mostly filler. (3) If "active" ingredients have tiny amounts (50mg in a 2000mg serving), the rest is filler. (4) If the powder is pure white and flows like sugar, it's likely maltodextrin-heavy. (5) Compare price per active ingredient—cheap supplements use fillers to appear affordable. Quality supplements have short ingredient lists with whole foods or concentrated extracts, not long lists of inactive additives.

Are natural fillers better than synthetic fillers?

Natural fillers are generally better, but the best option is minimal fillers period. Natural fillers like rice flour, tapioca starch, or cellulose are less concerning than synthetic ones like maltodextrin or propylene glycol—they're less processed and less likely to cause reactions. However, they still dilute active ingredients and add no nutritional value. The optimal approach is whole-food formulations where ingredients naturally bind without requiring separate fillers. For example, air-dried organ meat holds together naturally without needing binders, flow agents, or bulking agents.

What should I look for in a clean dog supplement?

A clean supplement has: (1) Short ingredient list—only active ingredients and minimal processing aids. (2) Whole-food sources—beef liver, fish, kelp instead of synthetic isolates. (3) No maltodextrin, artificial colors, or excessive starches. (4) Transparent sourcing—specifies where ingredients come from. (5) High concentration of actives—serving size reflects real food, not filler bulk. (6) Minimal processing—freeze-dried or air-dried instead of high-heat rendered. (7) Third-party testing for purity. Look for supplements where you recognize every ingredient as actual food, not chemical additives.

Can fillers cause allergies or sensitivities in dogs?

Yes, some fillers can trigger reactions in sensitive dogs. Common culprits include: (1) Corn-derived maltodextrin (dogs with corn sensitivities). (2) Soy lecithin (dogs with soy allergies). (3) Wheat or rice flour (grain sensitivities). (4) Artificial colors (potential allergens and behavioral reactions). (5) Preservatives like BHA/BHT (digestive upset or skin reactions). (6) Gums and starches (digestive issues in some dogs). If your dog has food sensitivities, choose supplements with minimal ingredients and avoid common allergen fillers. Whole-food supplements without fillers reduce reaction risk.