What is milk thistle?
Milk thistle is a thistle (daisy family) native to the Mediterranean, and its seed extract, silymarin, is the main active ingredient. It has long been a folk remedy for liver disease in Europe and is one of the best-selling "liver supplements" in Korea.
Korea's MFDS approves milk thistle extract for "may help liver health" at 130 mg of silymarin a day. On the label, look for "silymarin ___ mg," not "milk thistle extract ___ mg"; the extract weight and the silymarin content are different.
When are checkup liver results too high?
Korean health checkups grade liver tests as below under the national checkup standards (units: U/L). Lab reference ranges can differ slightly, so also check the range printed on your report.
| Test | Normal A | Normal B (borderline) | Suspected disease |
|---|---|---|---|
| AST | 40 or below | 41–50 | 51 or above |
| ALT | 35 or below | 36–45 | 46 or above |
| GGT (men) | 11–63 | 64–77 | 78 or above |
| GGT (women) | 8–35 | 36–45 | 46 or above |
Common causes of raised liver enzymes are fatty liver (linked to obesity and diabetes), alcohol, medications or supplements, and hepatitis B or C. Hard exercise the day before can also raise AST from muscle. Because the response depends entirely on the cause, find the cause before choosing a supplement.
What does the research show?
| Condition | Findings | Strength of evidence |
|---|---|---|
| Alcohol-related liver disease, hepatitis B or C | A Cochrane review (2007; 13 trials, 915 people) found no statistically significant difference from placebo in deaths, liver complications or liver tissue. Looking only at rigorous trials, liver-related deaths did not clearly fall either. | No effect shown |
| Non-alcoholic (metabolic) fatty liver | A meta-analysis (2017; 8 trials, 587 people) found lower AST and ALT with silymarin. The trials were small and varied in dose and length, and improvements in actual outcomes such as liver fibrosis were not shown. | Possible, uncertain |
| "Protecting" a healthy liver | No human study shows it prevents liver disease in people without liver disease. | No evidence |
The US NCCIH likewise concludes that whether milk thistle helps liver disease remains unresolved. It may modestly lower enzyme levels, but it cannot replace managing the root causes of fatty liver: weight, alcohol and blood sugar.
Milk thistle myths: true or false?
| Claim | What the evidence shows so far |
|---|---|
| Take it before drinking and you will not get a hangover | There is no human clinical evidence that it reduces hangovers, and it showed no benefit even in people with alcohol-related liver disease. |
| High liver enzymes? Start with milk thistle | It is the other way round: check first for hepatitis viruses, medications or fatty liver, each of which has its own treatment. |
| Natural means safe for the liver | In the US Drug-Induced Liver Injury Network, the share of liver injury caused by herbal and dietary supplements rose from about 7% to 20%. Stacking several "liver" products can itself burden the liver. |
| More is better | The Korean standard is 130 mg of silymarin a day; there is no evidence that more works better. |
Be careful with milk thistle if you
- Are allergic to plants in the daisy family (ragweed, chrysanthemum, daisy); allergic reactions can occur.
- Notice digestive side effects such as diarrhea, bloating or nausea, the most common ones.
- Take diabetes medication: It may lower blood sugar, so watch your glucose.
- Are being treated for liver disease or take several medications; talk to your doctor or pharmacist first.
See a doctor before reaching for a supplement if
- Your checkup shows AST or ALT in the "suspected disease" range, or borderline results year after year
- The whites of your eyes or your skin turn yellow, or your urine turns cola-dark
- You carry hepatitis B or C, or drink heavily and often
- Fatigue, nausea or itching started after a new medication or supplement
Please keep in mind
- This article is based on information checked as of the date shown at the top. New research or changes in official guidelines may change the details, so please use it as a reference rather than taking it as definitive.
- For an accurate diagnosis and advice about your health, please see a doctor in person.