Milk Thistle and 'Liver Detox' Supplements: What the Evidence Shows

If a blood test showed high liver enzymes or a scan mentioned fatty liver, a “liver support” supplement can look like an easy fix. Milk thistle, a purple-flowered plant whose extract is called silymarin, is the best-known ingredient.¹ Here is what federal researchers say.

What the evidence shows

The National Center for Complementary and Integrative Health (NCCIH)¹ says there isn’t enough high-quality evidence to draw firm conclusions about milk thistle.¹

• Liver disease: trials in alcohol-related liver disease, hepatitis B and C, fatty liver disease and liver damage from chemotherapy or toxins have been conflicting or too limited.¹
• Two NCCIH-funded studies, one in hepatitis C and one in an advanced form of fatty liver disease, found no benefit from silymarin.¹
• Blood sugar: a few small studies, mostly from Middle Eastern countries, suggest it may help control blood sugar in type 2 diabetes, but it’s unclear whether results apply elsewhere.¹

About “detox” claims

NCCIH found no compelling research that detox programs remove toxins from the body.² The FDA and FTC have acted against some detox products for hidden ingredients or false claims.² Our article on colon hydrotherapy covers another detox trend.

Safety and quality

• Milk thistle is usually well tolerated. Side effects include bloating, nausea and gas.¹
• Quality varies. Some products contained much more or less silymarin than the label said, or were contaminated with pesticides, microbes or mold toxins.¹
• Allergies are possible, especially if you react to ragweed, chrysanthemums, marigolds or daisies.¹
• Medicine interactions are possible, so check with your pharmacist.¹

What helps a fatty liver

If you’ve been told you have fatty liver, ask your clinician about the plan for your weight, blood sugar, cholesterol and alcohol use, and how they’ll monitor your liver. A supplement isn’t a substitute for that follow-up.

Before you buy

1. Tell your clinician about any liver supplement, especially before blood tests.
2. Choose a single-ingredient product with third-party quality testing if you decide to try one.
3. Skip “detox” blends with long ingredient lists.
4. Watch for warning signs such as yellow eyes, dark urine or pale stools.

Try: “My liver tests were a little high and I’ve been taking milk thistle. Is it safe with my medicines, and what should we do to find and treat the cause?”

Bloated by Dinner includes a Belly Clock log and a Test-It list with a visit script. Use them to list supplements, symptoms and test results for your appointment. See the book.