L-Proline

L-proline reference formula with an example 2,000 mg per serving, developed as a powder or a capsule, with the final amount set by the brand.

L-Proline is a reference formula for brands building a single-ingredient amino acid product, with L-proline declared by weight. The example serving carries 2,000 mg of L-proline, and the brand sets the final amount, the grade and the format for its market.

A powder carries the example amount, and capsules are the format with the most reference labels, usually at several capsules per serving. The development work centers on the purity and optical form of the amino acid, the handling of a hygroscopic crystalline powder, and the capsule count needed for a gram-level dose.

Ingredient Composition

IngredientPer ServingRaw Material FormAlternative Form (same amount of active)
L-Proline2000 mg (example amount)L-proline free-form crystalline powder (fermentation grade); specification 2,000 mg per serving, with assay, optical rotation and moisture set with the supplierL-proline hydrochloride at the weight that gives the same free L-proline, with the basis stated

The amount is the weight of L-proline as declared on the label, so the assay and the form are part of the specification and are not inferred from the weight. The label names the ingredient as L-proline; a salt form, if used, is declared on a stated basis.

Intended Benefits & Formula Rationale

This formula is designed for products positioned around amino acid nutrition and connective tissue ingredients. L-proline is included as the single active so that the grade, the moisture control and the format can be set around one ingredient.

Intended Benefit DirectionKey IngredientsFormulation Rationale
Amino acid nutritionL-ProlineProline plays roles in protein synthesis and structure, in metabolism including the synthesis of arginine, polyamines and glutamate, and in wound healing, antioxidative reactions and immune responses; the review considers it a functional amino acid and calls for further research on dietary supplementation with proline in humans [1]. Evidence: Referenced
Cell-level antioxidant roleL-ProlineIn a laboratory study on sperm samples from 30 healthy men, 2 mmol/L L-proline added to the incubation medium maintained sperm motility, viability and total antioxidant capacity over 24 hours; the study is an in vitro study and not a supplement trial [2]. Evidence: Referenced (in vitro)

The example amount is the first trial dose; the brand fixes the final amount and the format for its market.

Available Formats

The reference formula is built for a powder version and a capsule version; counts per serving are design choices that the brand can adjust.

FormatUnitPer ServingPack SizeOther Ingredients (typical)Suitability
Powder1 scoop2000 mg L-proline30 servings per tubNatural flavor, sweetener, flow agentCarries the example amount; mixes into water
Capsule4 capsules2000 mg L-proline120 or 240 capsulesCapsule shell, flow agentCapsule version at 500 mg per capsule

Raw Material Input & Fill (Design Estimate)

Design estimates. L-proline is assumed at 100% of the declared weight and a bulk density of 0.7 g/mL, so a size 00 capsule holds about 500 mg of amino acid with a small flow agent allowance.

FormatRaw Material Input per UnitDesign FillBalance for ExcipientsVerification Before Scale-Up
Powder2000 mg per scoopAbout 3 g scoopAbout 1 g flavor, sweetener and flow agentSolubility, taste, caking, moisture, assay
Capsule500 mg per capsuleAbout 510 mg in a size 00 capsuleAbout 10 mg flow agentBulk density and flow, fill weight variation, assay, moisture

Tablet and liquid versions are separate projects, because a gram-level amino acid dose needs its own compression or solubility study in those formats.

Formulation Considerations

Hygroscopic powder. L-proline is very soluble in water and takes up moisture from the air, which can cake a powder or soften a capsule fill. Low-humidity filling, a desiccant in the bottle and a moisture limit are specified.
Taste. Proline has a sweet, slightly savory note at gram doses. A flavor system is tested at the full serving in the powder.
Capsule count. A 2,000 mg serving needs four capsules at 500 mg each. A smaller serving needs fewer capsules, and the brand sets the dose.
Evidence and claims. The cited review concerns proline as a functional amino acid and mainly reports animal work, and the second study is in vitro [1][2], so claims on a finished product are reviewed for each sales market before a product is developed.

Customization Options

Brands adjust the amount, the form and the format.

ParameterRangeNote
L-proline per serving410 to 3000 mg across the reference labelsGram doses need several capsules or a scoop
FormFree form or hydrochlorideBasis stated on the label
FormatPowder or capsuleTablet and liquid are separate projects
Flavor systemUnflavored, citrusUsed in the powder
Add-onsL-lysine, vitamin CEach add-on changes the blend and the label

The pilot run confirms the powder flow and moisture, the capsule fill weight and the assay of the first fills.

Flavor Options

FormatSuggested FlavorsWhy
PowderUnflavored, citrusCitrus notes suit an amino acid drink

Technical Status & Data Sources

ItemStatusDetails
Reference formulaNIH DSLDThe ingredient and amount come from a labeled product in the NIH DSLD (2000 mg on the label of CF004018; example DSLD labels 23147, 251949, 252818). The label names the ingredient as L-proline.
SpecificationSet in formulationL-proline, 2,000 mg per serving; assay, optical rotation, moisture, heavy metal and microbial limits and methods are fixed with the supplier. Unit size, fill weight and stability are set in formulation.
Data sourceNIH DSLDDSLD v9.4.0, downloaded 2026-01-10: 50,824 reference formulas merged from on-market labels with complete ingredient amounts. Counts show how labels are distributed.
Market reviewPer marketDose limits, labeling and claims are reviewed for each sales market before a finished product is developed.
ReferencesSources[1] Wu G, Bazer FW, Burghardt RC, et al. Proline and hydroxyproline metabolism: implications for animal and human nutrition. Amino Acids. 2011;40(4):1053-1063. DOI · PubMed<br>[2] Moradi M, Moradi B, Hashemian AH, et al. Beneficial effect of L-Proline supplementation on the quality of human spermatozoa. Andrologia. 2022;54(8):e14486. DOI · PubMed

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