Milk thistle

What is milk thistle (silymarin)?

According to NCCIH, milk thistle is a tall plant native to Europe with large purple flowers; it was brought to North America by early colonists. The main component of its extract is silymarin, a mixture of compounds. It has been used historically for liver diseases and to increase breast milk; today it is marketed as a supplement for liver diseases, diabetes, and other conditions. ^[1] In the Ministry of Agriculture and Forestry Plant List, Silybum marianum is cited as “Meryem Ana dikeni, devedikeni” (milk thistle) with its fruit, seed, leaf, and aerial parts. ^[8]

Silymarin is not a single substance but a mixture; the Restricted Substances List in Türkiye likewise defines separate rows for silymarin and “silibinin.” ^[9] A “silymarin” dose in a study may therefore not be the same as “silibinin” or the total extract amount on a label.

Role in the body and purpose of use

Milk thistle is not a nutrient; it has no required function in the body and no deficiency. Its purpose of use is to “protect” the liver; however, NCCIH reports that there is not enough high-quality evidence to reach firm conclusions about its effects in humans. ^[1] In the sections below, the claims are separated by disease type; for people with liver disease, this information is not a treatment recommendation.

Does milk thistle work in hepatitis C?

The JAMA study by Fried and colleagues is a double-blind, placebo-controlled RCT conducted at 4 centers in the US. 154 people with chronic HCV, who had previously failed interferon-based treatment and had an ALT level of 65 U/L or above, were randomized into three groups: two different high silymarin doses and placebo; duration was 24 weeks. Only 2 people in each group reached the primary endpoint (ALT falling to normal or decreasing by at least 50%) (placebo 3.8%, low dose 4.0%, high dose 3.8%; P ≥ 0.99). The mean fall in ALT did not differ significantly between groups (P = 0.75); there was also no difference in HCV RNA and quality-of-life measures; the adverse event profile was similar to placebo. The study was NIH-funded. ^[2]

The meta-analysis by Yang and colleagues pooled 5 RCTs (222 silymarin, 167 placebo) comparing silymarin (or intravenous silibinin) with placebo in people with chronic HCV. In those taking oral silymarin, the change in HCV RNA did not differ from placebo (P = 0.19), nor did the effect on ALT (P = 0.45); quality-of-life improvement was similar in the two groups. The authors state that oral silymarin was tolerated but that no evidence of benefit was reported for intermediate endpoints (ALT, HCV RNA). They add that more studies are needed for intravenous administration. ^[3]

Is milk thistle effective for fatty liver (NAFLD/NASH)?

The study by Navarro and colleagues is an exploratory, double-blind, placebo-controlled phase II RCT conducted at 5 centers in the US. NASH patients without cirrhosis were given a standardized silymarin preparation (two different high doses) or placebo for 48 weeks. 116 people were screened, and 78 were randomized. The primary endpoint (histologic improvement of at least 2 points in NAS) was reached by 4/27 (15%) at the 700 mg dose, 5/26 (19%) at the 420 mg dose, and 3/25 (12%) in the placebo group (p = 0.79); the authors stated there was no benefit in the intention-to-treat analysis. On central pathologist review, 49 participants (63%) were reported not to meet the histologic entry criteria, and fibrosis improved most in the placebo group (without a significant difference); for these reasons, the authors judged the effect of silymarin in NASH to be inconclusive. There was no significant between-group difference in adverse events. ^[4] The article’s correction concerns only one author’s name (PLoS One 2019;14:e0223915).

The 2024 meta-analysis by Li and colleagues pooled 26 RCTs (2,375 patients) in NAFLD/NASH. Silymarin significantly lowered total cholesterol (SMD −0.85; 95% CI −1.23 to −0.47), triglycerides (−0.62; −1.14 to −0.10), LDL-C (−0.81; −1.31 to −0.31), and fasting insulin (−0.59; −0.91 to −0.28) and raised HDL-C (0.46; 0.03–0.89); for HOMA-IR, the summary counts this reduction as significant too, but the reported confidence interval includes 0 (SMD −0.37; −0.77 to 0.04). ALT and AST were found to be lower, and steatosis improved on liver histology (OR 3.25; 95% CI 1.80–5.87). The authors stated that the effects need to be confirmed by further research. ^[5] Read side by side, the two results look like this: the laboratory and histology improvements in the meta-analysis do not agree with the “no difference” result for the primary endpoint of the NIH-funded phase II RCT; the two results answer the same question with different study types. NCCIH describes the results for NAFLD as conflicting or too limited to reach a conclusion. ^[1]

Does milk thistle prevent liver injury from tuberculosis drugs?

The meta-analysis by Tao and colleagues (search through November 30, 2018) included 5 RCTs (1,198 patients; 585 silymarin, 613 placebo) comparing silymarin with placebo for preventing antituberculosis drug–induced liver injury (DILI). Silymarin significantly reduced the occurrence of DILI at week 4 (RR 0.33; 95% CI 0.15–0.75); there were also small reductions in ALT, AST, and ALP levels (SMD −0.15, −0.14, and −0.12). Adverse events were similar to placebo (OR 1.09; 95% CI 0.86–1.39). ^[6] This is a single meta-analysis; this information does not provide a basis for changing the drug regimen of a person undergoing tuberculosis treatment.

Does milk thistle lower blood sugar in diabetes?

The meta-analysis by Voroneanu and colleagues covered 5 RCTs (270 patients) in type 2 diabetes: fasting blood glucose fell by 26.86 mg/dL (95% CI −35.42 to −18.30) and HbA1c by 1.07 (95% CI −1.73 to −0.40), with no effect on the lipid profile. The authors stated that no recommendation can be made because of the low quality of the evidence and high heterogeneity. ^[7] NCCIH likewise reports that a small number of studies show milk thistle extracts may help control blood sugar in type 2 diabetes, but that most of the research was done in Middle Eastern countries and it is uncertain whether the same results would be seen elsewhere in the world. ^[1]

The 2025 meta-analysis by Yin and colleagues focused on insulin resistance and sensitivity: 6 studies (673 participants) from Iran, Egypt, and Italy were included, all at low risk of bias. HOMA-IR fell compared with placebo (mean difference −2.29; 95% CI −4.55 to −0.03; p = 0.047), while fasting insulin did not change (−2.56; 95% CI −7.60 to 2.48). In subgroups, HOMA-IR improvement was seen in type 2 diabetes and in diabetics with alcoholic cirrhosis, but not in NAFLD patients. The authors state that the evidence is limited and that these parameters did not improve significantly overall. ^[10]

Does milk thistle affect breast milk and other conditions?

NCCIH reports that it is uncertain whether milk thistle affects breast milk production and that it is unknown whether it is helpful in other conditions. ^[1] For conditions such as alcohol-related liver disease, hepatitis B, and chemotherapy-related liver problems, NCCIH states that results are conflicting or too limited to reach a conclusion; the NIH-funded hepatitis C and NASH studies showed no benefit from silymarin extract. ^[1]

Is milk thistle safe, and are there quality problems?

According to NCCIH, when taken orally, milk thistle is generally well tolerated; the most common side effects are digestive symptoms such as bloating, nausea, and gas. Allergic reactions may occur, particularly in people allergic to related plants such as ragweed, chrysanthemum, marigold, and daisy. Little is known about its safety in pregnancy and breastfeeding. ^[1]

NCCIH also reports that concerns have been raised about the chemical and microbiological quality of milk thistle supplements: in some products the amount of silymarin was found to differ substantially from the amount on the label, and in some, contamination with pesticides, microorganisms, or mycotoxins (mold toxins) was detected. ^[1] A result measured in studies therefore cannot be automatically transferred to any product on the market.

What is milk thistle’s status in Türkiye?

In the July 16, 2026 update of the Ministry of Agriculture and Forestry Plant List, Silybum marianum (fruit, seed, leaf, aerial parts) is listed as positive (P). ^[8] In the September 21, 2026 version of the Dietary Supplements Restricted Substances List, there are two separate rows: 900 mg/day for “Silymarin (from Silybum marianum extract)” (published June 27, 2016) and 450 mg/day for “Silibinin (from Silybum marianum extract)” (published March 9, 2017); both are in the ages 11 and over maximum column, and the ages 4–10 columns are empty. ^[9] These limits are marker compound amounts and separate units; they are not in the same unit as the total extract weight used in studies. Dietary supplements are also covered on the Supplement regulation in Türkiye page. This guide does not recommend products or suppliers and does not set personal doses.

Evidence table: claim, population, and limits