Milk Thistle Extract

Single-ingredient milk thistle extract reference formula at 250 mg per serving, developed as a capsule or softgel.

Milk Thistle is a reference formula for brands building a single-ingredient botanical extract product at a default amount of 250 mg of milk thistle extract per serving. The extract is the only active ingredient, so the development work centers on the standardization of the extract (silymarin content), the fill weight of a botanical powder, and the capsule or softgel system that carries it.

Capsule is the lead format because a 250 mg extract blends into a standard fill, while the softgel suspends the extract in an oil base. Reference labels also include whole seed powders at gram-level amounts, and these are a different raw material from a standardized extract, so the page is built around the extract.

Ingredient Composition

IngredientPer ServingRaw Material FormAlternative Form (same amount of active)
Milk Thistle250 mg (default amount)Milk thistle fruit extract standardized to silymarin, for example the Milk Thistle Extract 70–80% Silymarin grade; specification 250 mg extract per serving, silymarin content set with the supplierGeneral Milk Thistle Extract Powder with a different silymarin content, with the input recalculated so that the silymarin amount per serving is kept

Amounts are stated as mg of milk thistle extract, not of silymarin. Silymarin is a mixture of flavonolignans in which silybin is the main component [2], so the silymarin amount per serving equals the extract weight multiplied by its assay. A 250 mg serving of a 70–80% extract carries about 175 to 200 mg of silymarin, and a grade with a different assay changes that number and the input weight.

Intended Benefits & Formula Rationale

This formula is designed for products positioned around botanical liver nutrition. Milk thistle extract is included as the single active so that the standardization, the amount and the excipient system can be set without interaction with other actives.

Intended Benefit DirectionKey IngredientsFormulation Rationale
Traditional botanical nutritionMilk ThistleIncluded as a therapeutic herb with a 2,000-year history of use, whose fruits contain the flavonolignan mixture known as silymarin [2]. Evidence: Referenced
Liver nutritionMilk ThistleA review of the clinical potential in alcoholic and nonalcoholic fatty liver disease, viral hepatitis and drug-induced liver injury concluded that, despite encouraging preclinical data, further well-designed randomized trials are needed to substantiate the value of milk thistle preparations [2]. Evidence: Mixed

The extract weight stays fixed while the silymarin grade moves. A safety review reports that silymarin is safe in humans at therapeutic doses and is well tolerated at 700 mg three times a day for 24 weeks, with some nausea and diarrhea [1], so the amount, the claims and the target market are brand decisions reviewed per market.

Available Formats

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

FormatUnitPer ServingPack SizeOther Ingredients (typical)Suitability
Capsule1 capsule250 mg extract60 or 120 capsulesRice powder, flow agent, gelatin or vegetable capsule shellLead format; extract in a standard fill
Softgel1 softgel250 mg extract60 or 90 softgelsVegetable oil, suspending agent, gelatin or plant-based shell, glycerinExtract suspended in an oil base

Raw Material Input & Fill (Design Estimate)

Design estimates. The input is the labeled extract weight at an assumed 100% assay of the extract as purchased, so 250 mg of extract per serving is used as the input; the silymarin content follows from the extract grade and is set in the specification.

FormatRaw Material Input per UnitDesign FillBalance for ExcipientsVerification Before Scale-Up
Capsule250 mg extract330 mg per capsule80 mgFlow, fill weight variation, silymarin assay, moisture
Softgel250 mg extract600 mg fill350 mgSuspension homogeneity, shell compatibility, silymarin assay

Powder and liquid versions are separate projects, because whole-seed powders at gram amounts and liquid extracts in milliliters are different raw materials with their own specifications.

Formulation Considerations

Standardization drives the input. The same 250 mg of extract carries a different silymarin amount from each grade. The page therefore fixes the extract weight and leaves silymarin content to the specification, and any change of grade changes the labeled silymarin amount.
Botanical powder handling. A dry botanical extract is hygroscopic and can be cohesive, so moisture, flow and bulk density are checked on the received lot before a fill weight is set. The balance of excipients in the capsule is sized for the density of the chosen grade.
Softgel suspension. In an oil base the extract is suspended, not dissolved. Particle size and the suspending agent decide whether each softgel carries the same extract weight, and settling is checked during fill and storage.
Safety and market review. The safety review in [1] advises caution in pregnancy and with drugs that have a narrow therapeutic window. Label statements follow the rules of each sales market and are reviewed before a product is developed.

Customization Options

Brands adjust the extract weight, the silymarin standardization, the format and the add-ons.

ParameterRangeNote
Extract per serving175, 200, 250 or 450 mgOptions for the brand; capsule fill weight scales with the tier
StandardizationSilymarin grade set with the supplierChanges the silymarin amount per serving and the input weight
FormatCapsule or softgelPowder and liquid are separate projects
Pack size30 to 120 unitsSet by the brand
Add-onsDandelion, turmeric, artichokeA second botanical changes the fill weight and the specification

The pilot run confirms flow and fill weight of the extract blend, suspension homogeneity in the softgel, and the silymarin assay of the first units against the specification.

Technical Status & Data Sources

ItemStatusDetails
Reference formulaNIH DSLDThe ingredient and amount come from a labeled product in the NIH DSLD (250 mg on the label of CF008218; example DSLD labels 62149, 72499, 228398). The label names the ingredient as milk thistle extract; a silymarin-standardized fruit extract is set as the form.
SpecificationSet in formulationMilk thistle fruit extract, 250 mg per serving, standardized to silymarin; silymarin assay, solvent residue, pesticide and heavy-metal limits and method 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] Soleimani V, Delghandi PS, Moallem SA, et al. Safety and toxicity of silymarin, the major constituent of milk thistle extract: An updated review. Phytother Res. 2019;33(6):1627-1638. DOI · PubMed<br>[2] Abenavoli L, Izzo AA, Milić N, et al. Milk thistle (Silybum marianum): A concise overview on its chemistry, pharmacological, and nutraceutical uses in liver diseases. Phytother Res. 2018;32(11):2202-2213. DOI · PubMed

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