A clear glass bowl containing capsules filled with tan and brown powders. It is surrounded by different nutraceutical ingredients, liquids, oils, and powders.

What Are the Best Nutraceutical Ingredients for Empty Capsules?

Capsules remain one of the most popular supplement delivery systems due to their enhanced absorption, convenience, customizable dosing, and more.1 Not every nutraceutical ingredient is easy to encapsulate, though. Ingredients with poor flowability, high moisture sensitivity, or unusual particle sizes can cause challenges during manufacturing. These could create potential risks such as inconsistent capsule weights, production delays, or even compromised product quality.

This article offers a summary of nutraceutical ingredients that are well-known for their compatibility with empty capsules, consistent performance, and widespread use in the supplement industry to assist manufacturers in choosing ingredients that complement capsules. We’ll also discuss ingredients that might experience trouble during encapsulation and how producers might deal with typical capsule production issues.

What Makes a Nutraceutical Ingredient “Capsule-Ready”?

Choosing ingredients suitable for capsules involves more than just considering their nutritional benefits. Manufacturers need ingredients that fill consistently, maintain stability, and meet quality standards. Here are some important factors to keep in mind:

Good Flow Properties

Flowability, which is how easily a powder moves during manufacturing, is critical for successful encapsulation.2 Ingredients with good flow properties help ensure consistent capsule weights and dosing accuracy. Poor-flowing powders can clump or even clog capsule-filling equipment, causing production delays and inconsistent doses. Ingredients often benefit from excipients like magnesium stearate or silicon dioxide to improve flow and reduce sticking.

Uniform Particle Size

To increase the rate of each capsule having the correct amount of active ingredients, powder formulations need uniformly sized particles so powders can flow evenly into capsules.3 Irregular particle sizes can result in uneven filling, which ultimately affects dosage accuracy and amount. Finely milled or granulated ingredients with consistent particle distributions can mean smoother encapsulation.

Low Moisture Content

Particularly when manufacturing with hygroscopic ingredients, low moisture content in the encapsulation formulation is essential.4 Powders that absorb moisture easily can clump, degrade, or negatively interact with capsules themselves, affecting both the integrity and shelf life of the product. Dry ingredients ensure better stability and consistent filling performance.

Compatible with Gelatin or Vegetarian Materials

Ingredients used with vegetarian substitutes like HPMC capsules and pullulan capsules, or even with the animal-derived gelatin capsules, must be chemically and physically compatible. While HPMC capsules provide more stability for sensitive substances, gelatin capsules have higher moisture levels and might not be suitable for ingredients that are sensitive to moisture.5 Reactions like softening, brittleness, and cross-linking can be avoided by selecting the appropriate capsule material that works with the supplement formulation.

Meets Regulatory and Documentation Requirements

Like with any nutraceutical product, compliance with quality standards is of the utmost importance. Reputable bulk ingredient suppliers usually prioritize quality assurance, providing clear documentation, such as Certificates of Analysis (COAs), specifications, and statements verifying they meet regulatory standards. Proper documentation helps manufacturers stay compliant, ensures consistent quality, and streamlines regulatory audits.

A top view of a bowl of capsules filled with white, tan, and brown powder. The bowl is surrounded by other bowls, filled with nutraceutical ingredients such as seeds, oil, leaves, and powder.

Nutraceutical Ingredients That Work Well in Empty Capsules

Selecting ingredients specifically known for excellent capsule compatibility makes production efficient and reliable. Here are top choices:

  • Magnesium Citrate: A highly bioavailable source of magnesium, magnesium citrate is commonly utilized for bone, muscle, and digestive health products.6 What makes it ideal for encapsulation is that it flows smoothly, helping to ensure consistent dosing and reducing downtime.7
  • BCAA 2:1:1: Branch-chained amino acids (BCAA 2:1:1) are popular in sports nutrition and recovery products due to their support in muscle growth and repair. BCAAs in the 2:1:1 ratio of leucine, isoleucine, and valine are commonly encapsulated for precise dosing.
  • 5-HTP: Widely recognized for mood support, sleep, and stress relief supplements, 5-HTP is usually dosed in smaller, precise amounts, which is perfect for capsules.8
  • Magnesium Glycinate: Magnesium glycinate is known for its high bioavailability and gentle effect on the stomach.9 Its chemical stability along with compatibility with capsule materials make it a good choice for encapsulation.10
  • Magnesium Oxide: Providing a high concentration of elemental magnesium, magnesium oxide is commonly used to support digestive health.11 Magnesium oxide’s powder properties typically allow for efficient encapsulation, though attention to particle size and flow characteristics is important to ensure uniformity.

Nutraceutical Ingredients That May Require Extra Attention for Encapsulation

Certain nutraceutical ingredients have significant health benefits but can be challenging to work with during encapsulation. With solutions such as adjustments to the production environment and the addition of excipients to the formulation, these ingredients can still be encapsulated effectively:

Hygroscopic Ingredients (Moisture-Sensitive)

Hygroscopic ingredients that absorb moisture from the environment can lead to clumping, sticking, or degradation of the active ingredient. Without the correct measures, these issues can slow down production or affect overall product quality.

  • Calcium Ascorbate (Buffered Vitamin C): A non-acidic, gentle form of vitamin C usually used for immune support supplements,12 calcium ascorbate is sensitive to moisture, which can cause powder clumping and capsule filling issues.13 Be sure to maintain a low-humidity environment during production to help mitigate this.
  • Sodium Citrate: Sodium citrate supports hydration and electrolyte balance in supplements and sports formulations.14 This ingredient is also hygroscopic and absorbs moisture which can cause powder clumping.15 Controlling the production environment or adding flow-enhancing excipients such as silicon dioxide or microcrystalline cellulose should help.16
White capsules scattered against a white background.

High-Dose Ingredients

These ingredients are commonly used in larger quantities, which can exceed the fill limits of standard capsules. Formulators must consider capsule size and dosage per serving when working with these ingredients and capsules.

  • Magnesium Carbonate: Magnesium carbonate is typically employed as a digestive aid and general magnesium supplement. It can help provide support for digestion and bone health.17 If a supplement contains a large dosage of magnesium carbonate, standard capsule sizes may not work. Manufacturers can use larger capsule sizes or split the dosage into multiple capsules.
  • Creatine Monohydrate: With its well-established position in the fitness nutraceutical markets, creatine monohydrate supports energy production and muscular endurance. Effective dosages of creatine monohydrate may exceed standard capsule capacities.18 Smaller doses can be contained in multiple capsules, giving consumers the flexibility for their preferred intake.

Electrostatic or Handling Challenges

Some powders develop static or have physical traits that make them difficult to control during encapsulation. These issues can lead to powder sticking to machinery, inconsistent fills, or cross-contamination between runs.

  • Caffeine Powder: Caffeine powder is a fast-acting stimulant commonly used in energy, focus, and weight-management supplements. Its fine particle size and electrostatic charge can cause sticking, uneven flow, or dusting during capsule filling.19 Prevent static building by properly grounding equipment or blend the caffeine with flow agents like microcrystalline cellulose or magnesium stearate.
  • Glutamine Powder: Popular in sports and wellness supplements, glutamine supports muscle recovery, gut health, and more.20 Usually micronized, it is a very fine powder which can lead to clumping or poor flow.21 Consider using silicon dioxide in the formulation, or granulate the glutamine to facilitate proper filling in capsules.

Supporting Capsule Performance with Excipients

Excipients are inactive ingredients that have a significant effect on how effectively a formulation works during capsule filling.22 When used correctly, they can help solve common problems like poor flow, uneven fill weights, sticking, and clumping. These issues can impact production, and using the right excipients can help towards avoiding downtime.

  • Magnesium Stearate: A lubricant and flow enhancer, magnesium stearate reduces friction between powder particles and the capsule filling machine. This reduces instances of powder sticking and optimizes the formulation’s movement throughout the capsule filling process. It is particularly useful for sticky or electrostatic ingredients, and it enables smoother, faster capsule production.23
  • Microcrystalline Cellulose: Microcrystalline cellulose acts as a filler, binder, and flow aid.24 With encapsulated ingredients, it can add bulk so that each capsule is fully filled, especially when only a small amount of active ingredient is used. It is also used in encapsulation formulas to prevent ingredient segregation in blends with fine or light powders.
  • Silicon Dioxide: With its function as a glidant and anti-caking agent, silicon dioxide helps absorb surface moisture and coats particles, improving flowability and minimizing the risk of clumping or sticking.25 It is typically used in hygroscopic or sticky powders, such as amino acids. Silicon dioxide helps maintain consistency in capsule weights and addresses blockages or inconsistent flow, which can lead to downtime.

Incorporating these excipients helps manufacturers achieve consistent capsule weights, minimize downtime, and reduce product variability, leading to higher quality and efficiency.

Clear capsules filled with green powdered nutraceutical ingredients, next to a wooden bowl filled with the green nutraceutical ingredient powder.

What to Keep in Mind When Using Nutraceutical Ingredients in Capsules

If you are working with nutraceutical ingredients, empty capsules are a popular and effective delivery system. However, not every ingredient functions the same way, and even small differences can have an influence on your fill process, product quality, and productivity.

Here are a few things to keep in mind:

  • Flow isn’t always predictable. Even common ingredients like amino acids or botanicals can vary in their flow properties. Determine whether your formulation might need a flow aid or filler to help with capsule weight consistency.  
  • Some ingredients don’t work well with gelatin. Moisture-sensitive ingredients such as probiotics may degrade when used with gelatin capsules. A different type of capsule material, such as HPMC or pullulan, would work better.
  • Dosage size can be a limiting factor. If you’re using a high-dose ingredient like creatine or magnesium carbonate, plan for a larger capsule or multi-capsule serving—and adjust your labeling accordingly.
  • Consistency matters for manufacturing. Using nutraceutical ingredients with reliable specs and full documentation helps keep your production process smooth. It also reduces rework and supports compliance.

Encapsulating nutraceutical ingredients isn’t one-size-fits-all. Flowability, dosage size, and compatibility with capsule shells all affect how well an ingredient performs in production. But with the right planning and the right materials, capsules remain one of the most efficient and effective delivery forms for supplements.

Vivion supplies a wide range of nutraceutical ingredients and excipients, including empty gelatin, HPMC, and pullulan capsules, to support your full capsule formulation process. With consistent quality, dependable stock, and complete documentation, we help you keep production running smoothly. Contact us today to get a quote or request samples.

  1. https://www.spins.com/resources/blog/vitamins-supplements-and-sports-nutrition-key-trends-shaping-2024/ ↩︎
  2. https://pubmed.ncbi.nlm.nih.gov/23902366/ ↩︎
  3. ttps://encyclopedia.che.engin.umich.edu/2-capsules/ ↩︎
  4. https://www.ondrugdelivery.com/formulation-solution-for-moisture-sensitive-drugs/ ↩︎
  5. https://www.sciencepublishinggroup.com/article/10.11648/j.pst.20210502.14 ↩︎
  6. https://www.webmd.com/diet/health-benefits-magnesium-citrate ↩︎
  7. https://en.wikipedia.org/wiki/Glidant ↩︎
  8. https://www.webmd.com/vitamins/ai/ingredientmono-794/5-htp ↩︎
  9. https://www.healthline.com/health/magnesium-glycinate ↩︎
  10. https://consensus.app/home/blog/everything-you-should-know-about-magnesium-glycinate/ ↩︎
  11. https://drmicozzi.com/never-take-these-three-forms-of-magnesium ↩︎
  12. https://pubchem.ncbi.nlm.nih.gov/compound/Calcium-ascorbate ↩︎
  13. https://www.tandfonline.com/doi/full/10.1080/10942911003650338 ↩︎
  14. https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-citrate ↩︎
  15. https://go.drugbank.com/salts/DBSALT002410 ↩︎
  16. https://www.sciencedirect.com/science/article/pii/S2405844023037052 ↩︎
  17. https://www.drugs.com/international/magnesium-carbonate.html ↩︎
  18. https://www.health.harvard.edu/exercise-and-fitness/what-is-creatine-potential-benefits-and-risks-of-this-popular-supplement ↩︎
  19. https://pubmed.ncbi.nlm.nih.gov/18855912/ ↩︎
  20. https://my.clevelandclinic.org/health/articles/glutamine ↩︎
  21. https://www.sciencedirect.com/science/article/abs/pii/S0032591020300796 ↩︎
  22. https://en.wikipedia.org/wiki/Excipient ↩︎
  23. https://en.wikipedia.org/wiki/Magnesium_stearate ↩︎
  24. https://www.drugs.com/inactive/microcrystalline-cellulose-48.html ↩︎
  25. https://www.drugs.com/inactive/silicon-dioxide-170.html ↩︎

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