The Supplement Ratings
2026-03-28

The Most Common Fillers in Dietary Supplements

Every supplement has two ingredient lists: the Supplement Facts (active ingredients) and the Other Ingredients (inactive fillers, binders, flow agents). We analyzed the "Other Ingredients" of 116,409 supplements to understand what's really in your pills beyond the active ingredients.

Top 10 Most Common Inactive Ingredients

Based on our analysis of 116,409 product labels from the NIH DSLD:

  1. Gelatin — capsule material, generally recognized as safe (GRAS)
  2. Cellulose / Microcrystalline Cellulose — plant-based filler, GRAS
  3. Silicon Dioxide / Silica (36,591 products, 31%) — anti-caking agent. Generally safe at supplement levels but unnecessary.
  4. Magnesium Stearate (29,943 products, 26%) — lubricant for manufacturing. Debated but FDA considers safe.
  5. Stearic Acid — related to magnesium stearate, used as flow agent
  6. Glycerin — softgel component, safe
  7. Water / Purified Water — liquid formulations
  8. Citric Acid — pH adjuster, preservative, safe
  9. Rice Flour — filler, generally safe
  10. Sucralose (8,043 products, 7%) — artificial sweetener. Controversial — some studies raise concerns about gut microbiome effects.

Which Fillers Should You Actually Avoid?

Not all fillers are equal. Our scoring system classifies them into three tiers:

Avoid if possible (Tier 1): Titanium dioxide (banned in EU food), artificial colors (Red 40, Blue 1, Yellow 5), artificial sweeteners (sucralose, acesulfame K, aspartame), high fructose corn syrup, hydrogenated oils.

Questionable but common (Tier 2): Magnesium stearate, silicon dioxide, maltodextrin, soy lecithin, talc, carrageenan. These are FDA-approved but unnecessary — cleaner alternatives exist.

Acceptable (necessary for formulation): Cellulose, gelatin, glycerin, water, rice flour, citric acid, hypromellose. These are required to make capsules, tablets, and liquids.

How to Find Cleaner Supplements

Use our supplement search filtered by score 80+ — these products have the highest formulation cleanliness scores. Or browse our best-of rankings by category, which prioritize label quality.

Data source: NIH Dietary Supplement Label Database (DSLD). Analysis covers 116,409 products. See full methodology.