Best milk thistle supplement: how to read the label and what it can do
We research products from makers' specs and health sources; we do not run hands-on tests. Links to Amazon may earn us a commission at no cost to you. How this works.
- Standardized milk thistle extract, 80% silymarin. Best for: Adults who want a labeled silymarin amount. See options on Amazon
- Milk thistle with turmeric. Best for: People who want milk thistle and turmeric in one product. See options on Amazon
- Single-ingredient milk thistle capsules. Best for: People who want milk thistle without other herbs. See options on Amazon
What milk thistle is
Milk thistle (Silybum marianum) is a tall plant with large purple flowers, native to Europe and brought to North America by early colonists. The National Center for Complementary and Integrative Health (NCCIH) says the main constituent of milk thistle extract is silymarin, a mixture of compounds.
Historically it was used for liver disorders and to increase breast milk. Today it is promoted for liver disorders, diabetes and other conditions.
What the research shows
| Use | What NCCIH reports |
|---|---|
| Liver disease | Conflicting or too limited |
| Hepatitis C | No benefit in an NIH-funded trial |
| Fatty liver inflammation (NASH) | No benefit in an NIH-funded trial |
| Type 2 diabetes | May help blood sugar in small studies |
| Breast milk supply | Unclear |
NCCIH notes the diabetes studies were mostly done in Middle Eastern countries, and it is unclear whether results would be the same elsewhere. Trials for alcohol-related liver disease, hepatitis B, and liver problems from chemotherapy, low oxygen or toxins have been conflicting or too limited.
Milk thistle is not a treatment for liver disease. If you have a liver condition, work with your doctor.
The quality problem
This is a major buying issue. NCCIH says concerns have been raised about poor chemical and microbiological quality of milk thistle supplements in the United States and other countries. Some products have contained silymarin amounts substantially different from the label, or were contaminated with pesticides, microorganisms or mycotoxins (harmful substances made by molds or fungi).
Because of this, look for products that state a standardized silymarin amount in mg, and choose established brands that test their products.
Safety
- Generally well tolerated. The most common side effects are digestive: bloating, nausea and gas.
- Allergy. Milk thistle may cause allergic reactions, especially in people allergic to ragweed, chrysanthemum, marigold or daisy.
- Medicines. Talk with your health care provider before using it if you take any medicine.
- Pregnancy and breastfeeding. Little is known about safety. One NOW Foods milk thistle product is labeled not for pregnant or nursing women.
- Gallbladder. NOW Foods advises consulting a physician if you have gallbladder dysfunction.
Read the label: added herbs are common
Many milk thistle products are blends. NOW Foods' own products show how much they vary:
- Milk Thistle Extract 150 mg: per 2-capsule serving, 300 mg milk thistle extract standardized to 240 mg silymarin (80%), plus 700 mg turmeric root.
- Milk Thistle Extract Double Strength: per capsule, 300 mg extract with 240 mg silymarin, plus 100 mg dandelion root and 50 mg artichoke extract.
If you want milk thistle alone, check the full Supplement Facts panel. Added turmeric, dandelion or artichoke bring their own effects and cautions.
How to choose a milk thistle supplement
- Silymarin in mg. Look for a standardized extract that states silymarin, such as 80% silymarin flavonoids.
- Single herb vs blend. Decide whether you want added herbs.
- Quality signals. Choose products with clear standardization and from brands that test for contaminants.
- Dose. Follow the label; NOW Foods' directions range from 1 capsule once daily to 2 capsules three times daily, depending on the product.
- Form. Capsules and softgels are common; organic extracts are also sold.
What to look for when you buy
Standardized milk thistle extract, 80% silymarin
Best for: Adults who want a labeled silymarin amount
NOW Foods' Double Strength lists 300 mg extract standardized to 240 mg silymarin per capsule.
Watch out: Also contains dandelion and artichoke. Talk to your doctor if you have gallbladder problems or take medicines.
See options on AmazonMilk thistle with turmeric
Best for: People who want milk thistle and turmeric in one product
NOW Foods' 150 mg formula gives 240 mg silymarin and 700 mg turmeric root per 2-capsule serving.
Watch out: Labeled not for pregnant or nursing women. Turmeric has its own cautions, including liver concerns with high-absorption forms.
See options on AmazonSingle-ingredient milk thistle capsules
Best for: People who want milk thistle without other herbs
Avoids the added ingredients common in liver blends, so you know what you are taking.
Watch out: Check that silymarin is stated in mg, given quality concerns NCCIH describes.
See options on AmazonQuestions people ask
- What is the best milk thistle supplement?
- One that states a standardized silymarin amount in mg, lists all ingredients clearly, and comes from a brand that tests for contaminants. Decide whether you want added herbs.
- Does milk thistle help the liver?
- Evidence is conflicting or limited. Two NIH-funded trials found no benefit for hepatitis C or fatty liver inflammation.
- When is the best time to take milk thistle?
- Follow the label. Some products say to take it with food. Research has not set a best time.
- Is milk thistle safe?
- It appears well tolerated, with bloating, nausea and gas as the most common side effects. People allergic to ragweed or daisies may react.
- Can milk thistle lower blood sugar?
- Small studies suggest it may help in type 2 diabetes. Talk with your doctor first, especially if you take diabetes medicine.
Sources
- Milk Thistle: Usefulness and Safety (nccih.nih.gov), National Center for Complementary and Integrative Health
- Milk Thistle Extract 150 mg Silymarin (120 mg) Veg Capsules (www.nowfoods.com/products/supplements/milk-thistle-extract-150-mg-silymarin-120-mg-veg-capsules), NOW Foods
- Milk Thistle Extract, Double Strength 300 mg Veg Capsules (www.nowfoods.com/products/supplements/milk-thistle-extract-double-strength-300-mg-veg-capsules), NOW Foods