Milk thistle: what is it, what does it contain, and what should you look out for?

Short answer: Milk thistle (Silybum marianum) is a thistle native to the Mediterranean region. Supplements contain an extract of the seeds, and the best-known compounds in it are collectively called silymarin. If you’re pregnant, breastfeeding or allergic to plants in the daisy family, milk thistle isn’t for you.

Last updated: November 2, 2026 · Written by Florian Fermin

Milk thistle is one of the oldest herbs you’ll find in supplements, and yet we keep getting the same questions about it in chat. What’s in it, how much should you take, and can you combine it with medication? In this article, I’ll lay it all out, including what’s on our own label.

What is milk thistle?

Milk thistle is a type of thistle with purple flowers and large, green-and-white marbled leaves. The plant belongs to the daisy family (Asteraceae), like artichokes, chamomile and dandelions, and is native to the Mediterranean region. Milk thistle has been used for around 2,000 years (Abenavoli et al., 2018).

The name comes from an old legend: the white veins on the leaves are said to have come from drops of Mary’s milk. In English, the plant is called milk thistle; in German, Mariendistel; and in French, chardon-marie.

The seeds are used in supplements. Botanically, these are small fruits, which is why research often uses “fruits” or “fructus” instead of seeds.

What is silymarin?

Silymarin is the collective name for a group of compounds found in milk thistle seeds, known as flavonolignans. The main component is called silybin, also known as silibinin. So silymarin is not a single ingredient, but a mixture (Abenavoli et al., 2018).

The amount of silymarin in a supplement varies greatly from product to product. Some extracts are standardized to a fixed percentage of silymarin, while others list only an extraction ratio, such as 10:1. With a 10:1 ratio, 10 grams of seeds are reduced to 1 gram of extract. This tells you something about the concentration, but not how much silymarin it contains.

What does research say about milk thistle?

A lot of research has been done on silymarin, mainly in the lab and on animals. Studies in humans usually involve standardized extracts in a medical setting, with doses and groups that can’t be compared with an ordinary dietary supplement (Gillessen & Schmidt, 2020). The researchers themselves also note that more well-designed studies are needed (Abenavoli et al., 2018).

That’s why at GOYU, we don’t make promises about what milk thistle will do for you. No health claims for milk thistle have been definitively approved in the EU yet. The claims we use are still “on hold” with the European Commission. You can tell by the asterisk.

Who should not take milk thistle?

Our label states that milk thistle is intended for adults only and is not recommended during pregnancy or breastfeeding. It’s also unsuitable if you’re allergic to plants in the daisy family. So do not use milk thistle if you:

• are pregnant or breastfeeding
• are allergic to plants in the daisy family (Asteraceae), such as chamomile or artichoke
• are under 18

If you take blood thinners or other medications, consult your doctor or pharmacist first. A review of supplements and bleeding risk mentions milk thistle in relation to people taking blood thinners (Hatfield et al., 2022). If you have surgery coming up, also let them know that you take supplements.

How do you use milk thistle?

Our packaging says to take 1 capsule daily with water. We recommend taking it during or just after a meal. More isn’t better, so stick to one capsule a day. If you’re taking several products containing milk thistle, add up the amounts.

What should you look for when buying milk thistle?

Choose a milk thistle supplement based on the plant part, the content, and how thoroughly it’s been tested. The name on the front tells you little; the back tells you much more.

• Plant part: seed or fruit, because that’s where the silymarin is found.
• Content: a percentage of silymarin tells you more than a ratio such as 10:1 alone.
• Dosage: the amount of extract you get per day should be clearly stated on the label.
• Ingredients list: the shorter, the better. Check whether it contains fillers.
• Certificate of Analysis: a CoA for each batch shows that it has been tested for things including heavy metals and microbiology. Here’s how to read a CoA.

What’s on the packaging of our milk thistle?

Each capsule of our Milk Thistle Extract 500 mg capsules contains 500 mg of 10:1 milk thistle seed extract in a plant-based hypromellose capsule. That’s all: no fillers or colorants. Each pack contains 60 capsules, so at 1 capsule a day, it will last 60 days. As of November 2, 2026, a pack costs €15.95, which is about €0.27 per day.

To be honest: our label doesn’t state the silymarin content, only the extract ratio. If you’re specifically looking for an extract with a stated percentage of silymarin, we’re not the best choice. You can request a Certificate of Analysis (CoA) for your batch via support@getgoyu.com.

The following claims apply to our milk thistle:

• Milk thistle supports liver health*
• Milk thistle helps maintain liver function*
• Milk thistle contributes to the cleansing function of the liver*

Summary in 3 points

• Milk thistle is a thistle from the Mediterranean region. Supplements contain an extract of its seeds, with silymarin as the best-known group of compounds.
• Human studies mainly concern standardized extracts in a medical setting. No health claims for milk thistle have yet been definitively approved in the EU.
• Not suitable during pregnancy or breastfeeding, or if you have an allergy to the daisy family. If you take medication, consult your doctor or pharmacist first.

Frequently asked questions

Is milk thistle the same as silymarin?

No. Milk thistle is the plant; silymarin is a group of compounds from the plant's seeds.

When should you take milk thistle?

We recommend taking your capsule during or immediately after a meal. Taking it at the same time each day makes it easier not to forget.

Can you combine milk thistle with other supplements?

You can, but follow the dosage on each product's packaging. If you take medication, consult your doctor or pharmacist first.

How long does a package of milk thistle last?

Our package contains 60 capsules. At 1 capsule per day, that is 60 days.

Is milk thistle vegan?

Our capsules are. Both the extract and the hypromellose capsule shell are plant-based.

Sources

1. Abenavoli L, Izzo AA, Milić N, Cicala C, Santini A, Capasso R. Milk thistle (Silybum marianum): A concise overview on its chemistry, pharmacological, and nutraceutical uses in liver diseases. Phytother Res. 2018;32(11):2202-2213. doi:10.1002/ptr.6171
2. Gillessen A, Schmidt HH. Silymarin as Supportive Treatment in Liver Diseases: A Narrative Review. Adv Ther. 2020;37(4):1279-1301. doi:10.1007/s12325-020-01251-y
3. Hatfield J, Saad S, Housewright C. Dietary supplements and bleeding. Proc (Bayl Univ Med Cent). 2022;35(6):802-807. doi:10.1080/08998280.2022.2121575
4. Packaging text and GOYU Milk Thistle Extract 500 mg capsules product page, price checked on November 2, 2026.

You can find our milk thistle in the supplements for metabolism & liver collection.

*Health claim pending approval by the European Commission.

This article is for informational purposes only and is not medical advice. Dietary supplements are not a substitute for a varied and balanced diet and a healthy lifestyle. If in doubt, pregnant, or taking medication, consult your doctor or pharmacist.