The Science Behind It: Why is Glycerin Added to Supplements?

November 22, 2025 •

4 min read

Glycerin, also known as glycerol, is a versatile, sweet-tasting liquid that has been safely used in food, cosmetics, and pharmaceuticals for centuries. This multifunctionality is why glycerin is added to supplements, where it plays crucial roles from ensuring product quality to enhancing athletic performance.

Quick Summary

This article details why glycerin is a common and vital ingredient in many dietary supplements, highlighting its function as a stabilizer, solvent, moisture-retaining humectant, and flavor enhancer. It also explores its use by athletes for improving hydration and performance.

Key Points

Moisture Retention: Glycerin acts as a humectant, preventing supplements like gummies and protein bars from drying out and hardening.
Enhanced Stability: As a solvent, glycerin ensures active ingredients are uniformly distributed and remain stable in liquid formulas.
Improved Hydration: Endurance athletes use glycerin to induce hyperhydration, which increases total body water and can improve performance in hot conditions.
Better Taste: Glycerin provides a mild, low-glycemic sweetness, improving the flavor of supplements without relying on sugar.
Versatile Ingredient: It serves multiple functions across different supplement types, including softening softgels and thickening liquid products.
Safety Profile: Glycerin is generally considered safe for consumption, though excessive intake can cause mild side effects like bloating or headaches.

The Multipurpose Ingredient in Modern Supplement Formulations

Beyond just active ingredients, supplements rely on excipients, or inactive substances, to hold them together and ensure effectiveness. Glycerin is one of the most widely used of these excipients due to its unique chemical properties as a polyol or sugar alcohol. A clear, viscous, and odorless liquid, glycerin is highly soluble in water and is generally recognized as safe (GRAS) by the FDA. Its inclusion is a strategic decision for manufacturers seeking to improve product quality, stability, and consumer experience.

Glycerin as a Humectant and Stabilizer

One of glycerin's primary functions in supplements is its powerful humectant property, meaning it attracts and retains moisture. This is critical for several types of supplements:

Prevents drying and hardening: In softgel capsules and protein bars, glycerin helps prevent the product from drying out and becoming hard or brittle over time, ensuring a consistent and palatable texture.
Maintains moisture balance: For gummies and chewable supplements, glycerin's moisture-retaining ability keeps them soft and chewy, preventing crystallization and preserving freshness throughout the shelf-life.
Extends shelf-life: By maintaining proper moisture levels, glycerin inhibits microbial growth, acting as a preservative that extends the product's viability.

Glycerin as a Solvent and Carrier

Many active supplement ingredients, particularly botanical extracts and certain vitamins, are not easily dissolved in water or oil alone. Glycerin serves as an excellent solvent for these compounds. This is particularly important for liquid supplements and tinctures, as it ensures that the active ingredients are evenly dispersed and remain suspended in the solution. This uniform distribution is vital for delivering an accurate dose with every serving, enhancing the supplement's overall efficacy. As a carrier, glycerin helps stabilize these delicate ingredients and can improve their bioavailability, allowing for better absorption by the body.

A Low-Calorie Sweetener and Flavor Enhancer

Glycerin has a mildly sweet taste with a lower glycemic index than sugar. This makes it an ideal sugar alternative for sweetening liquid supplements, chewables, and protein bars without contributing to high sugar content or adding significant calories. This benefit is especially appealing to health-conscious consumers and those managing their sugar intake. Its ability to mask the bitter or unpleasant tastes of certain compounds also makes supplements more palatable and pleasant to consume.

Glycerin's Role in Athletic Performance Supplements

Athletes, particularly endurance athletes, have long used glycerin for its unique ergogenic properties. Glycerin's ability to draw and retain water in the body leads to a state known as hyperhydration.

Hyperhydration: When ingested with a large volume of fluids, glycerin increases the body's fluid retention by reducing urinary output. This expanded fluid volume helps regulate body temperature, reduce cardiovascular strain, and delay the onset of dehydration, which can significantly impair performance in hot conditions or during prolonged exercise. Some studies have shown that hyperhydration with glycerin can increase endurance time by up to 24%.
Enhanced "Pump": In the bodybuilding community, glycerin is often included in pre-workout supplements for its ability to draw extra water into muscle cells. This creates a more pronounced 'pump' or muscle fullness. While the link between the pump and long-term muscle growth is debated, the effect is a desirable aesthetic for many strength trainers.

A Comparison of Glycerin in Different Supplement Formats


Supplement Type	Glycerin's Primary Role(s)	Key Benefits for the Consumer
Liquid Supplements	Solvent, Stabilizer, Sweetener, Thickener	Ensures active ingredients are evenly mixed; provides a smooth, syrupy texture; improves taste without added sugar.
Softgel Capsules	Plasticizer, Stabilizer	Keeps the gelatin shell soft and flexible, preventing it from becoming brittle and cracking.
Gummies/Chewables	Humectant, Sweetener, Stabilizer	Preserves a soft, chewy texture; prevents hardening; enhances flavor without high sugar content.
Protein/Energy Bars	Humectant, Preservative	Retains moisture, preventing bars from drying out and becoming unpalatable over time.
Pre-Workout Powders	Performance Aid (Hyperhydration)	Increases fluid retention and total body water, delaying dehydration and potentially improving endurance.

Safety and Usage Considerations

While glycerin is widely considered safe for consumption, some precautions are necessary. The World Anti-Doping Agency (WADA) removed glycerin from its prohibited list in 2018, opening its use to competitive athletes again. However, individuals should be aware of potential side effects, especially at high doses. These may include headaches, dizziness, bloating, and gastrointestinal discomfort due to its mild laxative effect. As with any supplement, consulting a healthcare professional before use is recommended, particularly for specific medical conditions.

Conclusion: The Multifaceted Value of Glycerin

In conclusion, the addition of glycerin to supplements is a well-established practice driven by its diverse and beneficial properties. It is not merely a filler but a highly functional ingredient that contributes significantly to a product's overall quality, stability, and consumer appeal. Whether it's ensuring a smooth texture in a liquid tincture, keeping a protein bar moist, or providing endurance athletes with a hydration advantage, glycerin's role is far-reaching. Its ability to improve product attributes while offering potential performance benefits cements its status as a cornerstone of the modern nutraceutical industry. Given its GRAS status and versatile application, glycerin is set to remain a key component in supplement manufacturing for the foreseeable future. A further look into its use can be found in studies discussing glycerol use in athletic hydration, such as this one on PubMed: Guidelines for glycerol use in hyperhydration and rehydration associated with exercise.

Frequently Asked Questions

Chemically, they are the same compound. However, 'glycerin' is the commercial term used for the slightly less pure, commercial-grade product, while 'glycerol' refers to the pure chemical compound.

Yes, for endurance athletes, glycerin helps with hyperhydration by enabling the body to retain more fluid, which can improve thermoregulation and endurance, especially in hot environments. For strength trainers, it is sometimes used to enhance the 'muscle pump' effect.

In softgels, glycerin acts as a plasticizer, preventing the gelatin shell from becoming brittle and cracking over time. This helps maintain the capsule's integrity and ensures the contents remain potent.

The chemical properties are similar. However, vegetable glycerin, derived from plant oils, is often preferred by consumers seeking plant-based or naturally-sourced products.

Yes. Glycerin has a mild, sweet taste and a low glycemic index, making it a useful sugar alternative for improving the taste of supplements without adding high sugar content or calories.

Glycerin is generally safe, but excessive consumption may cause side effects such as headaches, bloating, nausea, or a laxative effect. These effects are typically dose-dependent.

In liquid formulas, glycerin functions as both a solvent and a stabilizer. It helps dissolve active ingredients evenly and provides a smooth, syrupy texture, preventing ingredients from separating over time.