Milk thistle (Silybum marianum) is one of the best-known botanical ingredients associated with the liver, and brands abroad regularly ask for a Japan-made milk thistle product built around its main active compound complex, silymarin.
This guide is for brand owners planning a milk thistle product made in Japan. It sets out what the clinical trial evidence actually shows, why the results vary by study and condition, Japan’s food status for the ingredient, and what to fix before asking for a quotation.
Health supplements are foods, not medicines, and are not a substitute for medical treatment. Nothing here is a claim that any product prevents, treats or cures a disease.
💬 Planning a milk thistle product made in Japan? We check the full formula against Japanese food law first. See Japan-made supplement OEM.
What the research shows
Silymarin’s effect on liver enzyme levels is inconsistent across studies and conditions, positive in some research settings and absent in others.
| Study | Design/What was analysed | Reported result |
|---|---|---|
| Systematic review, Cureus 2023 (PMID 38021897) | 29 randomised controlled trials, 3,846 participants across a range of clinical research populations, silymarin doses 140–420 mg | 65.5% of studies reported reduced liver enzyme levels, 20.7% no significant change, 13.8% higher liver enzymes; the authors described the effect as context-dependent, varying by condition, dose and comorbidities |
| Randomised, double-blind, placebo-controlled trial, JAMA 2012 (PMID 22797645) | 154 participants with chronic hepatitis C previously unsuccessful with interferon-based therapy; 420 mg or 700 mg silymarin or placebo, 3 times daily for 24 weeks | No significant difference between silymarin and placebo in the primary liver enzyme outcome, viral load, or quality of life; adverse events were comparable to placebo |
| Meta-analysis, Canadian Journal of Gastroenterology and Hepatology 2019 (PMID 30733935) | 5 randomised controlled trials, 1,198 participants receiving anti-tuberculosis drugs, silymarin versus placebo | Silymarin was associated with a lower rate of drug-induced liver injury at week 4 (RR 0.33) and with improvements in ALT, AST and ALP versus placebo; adverse events were similar between groups |
Three points worth keeping in view:
- Context dependence. The 2023 systematic review itself concluded that silymarin’s effect on liver enzymes varies with the condition being studied, the dose and other patient characteristics — it is not a uniform effect.
- A negative, well-controlled trial exists. The 2012 JAMA trial, run at four US medical centres with higher-than-customary doses, found no benefit over placebo in a specific clinical research population.
- Research populations. All three studies enrolled people in clinical research settings connected to a health condition. That is a fact about the research design, and it is not a basis for a disease-related claim about a supplement product sold to the general public.
Checked against the published abstracts on 25 September 2026.
What Japanese products say
Milk thistle sits on the Japanese list of ingredients not judged to be medicines unless a medicinal claim is made, which is why it is sold in Japan as a general food ingredient.
Japan’s food-drug classification system (食薬区分) maintains a list of substances treated exclusively as medicines and a separate list of substances not judged to be medicines provided the product does not claim a medicinal effect. Milk thistle (マリアアザミ, also known as オオアザミ), whole plant, sits on the non-medicinal list. That status supports its long-standing sale in Japan as a general food ingredient in capsules, tablets and extracts, through ordinary food retail channels rather than as a licensed medicine.
Being food-usable is a separate question from carrying a notified function. A Japanese company wishing to state a specific function for a milk thistle product under the Foods with Function Claims system would need its own notification and its own supporting evidence for that exact product.
💬 Need an evidence summary for your regulatory adviser that reflects the mixed research picture accurately? We prepare it with the manufacturing documents. Tell us your market.
Wording that stays on safe ground
Describe milk thistle by what has been studied, and be explicit that results vary — never attach it to a liver disease or condition.
| Safer wording | Wording to avoid |
|---|---|
| ”Contains milk thistle extract standardised to silymarin content” | Any liver-disease name, or “detox”, “repairs” or “cleanses” the liver |
| ”Studied in clinical research; results vary by study" | "Clinically proven” without naming which study, and its result |
| Naming the standardisation percentage and amount per serving | Implying a guaranteed effect on liver enzyme levels |
How milk thistle is formulated
Silymarin is poorly water-soluble, so most Japanese products use a standardised dry extract in capsule or tablet form rather than a raw powder.
| Dosage form | Why brands choose it | What to weigh up |
|---|---|---|
| Hard capsule | Simple, masks bitterness | Fits a standardised extract powder well |
| Tablet | Familiar format, stable | Binder and coating choice for a dense extract |
| Soft capsule | Can pair with an oil-based delivery system | Formulation work needed for a poorly water-soluble extract |
Decisions that shape the specification:
- Standardisation. Milk thistle extracts are conventionally standardised to a silymarin content (commonly expressed as a percentage). Ask the supplier for the standardisation method and the guaranteed percentage.
- Amount per serving. Match the amount to a specific study if you plan to cite one — trial doses above ranged from 140 mg to 700 mg of silymarin per dose.
- Companion ingredients. Milk thistle is often combined with other “healthy ageing” botanicals. Each companion ingredient needs its own check against Japanese food law.
- Your market’s status for milk thistle. Confirm its status as a food or supplement ingredient in each market you plan to sell in before committing to a formula.
The check that comes first
Every ingredient must be permitted in foods in Japan, or a Japanese factory cannot make the product.
Milk thistle itself is established in Japanese foods. Companion botanicals in combination “healthy ageing” or “detox” formulas are where a check most often turns up a problem. See the Japan-made supplement OEM page, and compare with our reishi mushroom and curcumin guides.
Before you ask for a quotation
A factory can quote accurately once the extract standardisation, the amount, the form and the companions are fixed.
- Milk thistle extract source and silymarin standardisation percentage
- Amount per serving and servings per pack
- Dosage form
- Companion ingredients and their amounts
- Countries you will sell in, and first order and annual volume
💬 Ready to design a Japan-made milk thistle product? Send us the concept — extract standardisation, amount, form and the countries you will sell in.
Frequently asked questions
1. Does milk thistle work for the liver?
Results vary. A 2023 systematic review of 29 trials found reduced liver enzyme levels in about two-thirds of studies, no change in about a fifth, and higher enzymes in the rest, describing the effect as context-dependent. A well-controlled 2012 JAMA trial found no benefit over placebo in one specific research population.
2. Why do the results differ so much between studies?
The 2023 systematic review attributed the variation to differences in the condition studied, the dose used and other patient characteristics, rather than a single consistent effect of silymarin itself.
3. Is milk thistle legal to sell as a food in Japan?
Yes. Milk thistle sits on Japan’s list of ingredients not judged to be medicines unless a medicinal claim is made, which is why it is sold there as a general food ingredient.
4. What dose was used in the studies above?
Doses ranged from 140 mg to 700 mg of silymarin per dose across the three studies cited here, given from once to three times daily depending on the trial.
5. Can I say my milk thistle product supports liver health?
Avoid disease-linked or organ-repair language. Describe the extract, its standardisation and the amount per serving, and reference the mixed research picture rather than implying a guaranteed effect.
Sources: “Impact of Silymarin Supplements on Liver Enzyme Levels: A Systematic Review”, Cureus 2023 (PMID 38021897); “Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy: a randomized controlled trial”, JAMA 2012 (PMID 22797645); “Prophylactic Therapy of Silymarin (Milk Thistle) on Antituberculosis Drug-Induced Liver Injury: A Meta-Analysis of Randomized Controlled Trials”, Canadian Journal of Gastroenterology and Hepatology 2019 (PMID 30733935); Japan Ministry of Health, Labour and Welfare 食薬区分における成分本質（原材料）の取扱いの例示. Checked on 25 September 2026.