Milk Thistle: What It Is and What Silymarin Means

Milk thistle is one of the oldest herbs in European gardens and one of the most marketed herbal supplements today, often with a lot of "detox" language attached. This guide sets the marketing aside and explains the facts: what the plant is, which part is used, what silymarin means on a label, how people take it and who should speak to a doctor or pharmacist first.

What is milk thistle?

Milk thistle (Silybum marianum) is a tall, prickly plant in the daisy family (Asteraceae), the same family as artichokes, dandelions and sunflowers. It has large purple flower heads and glossy green leaves marked with distinctive white veins. Folklore says the white marks came from drops of the Virgin Mary's milk, which is where the names milk thistle, Mary thistle and the species name marianum come from.

Milk thistle is not a vitamin or a mineral, and no health claims are authorised for milk thistle or silymarin in Great Britain. The word "detox" has no defined meaning in UK food law, and we do not use it on our labels.

Where does it come from?

Milk thistle is native to the Mediterranean and has spread across Europe, including parts of the UK, as well as North Africa, the Middle East and beyond. It was grown for centuries in monastery and cottage gardens. Historically, the young leaves were eaten like spinach, the flower heads were cooked like small artichokes and the roasted seeds were used as a coffee substitute.

Which part is used in supplements?

Supplements are made from the seeds, which botanically are small dry fruits. The seeds are pressed or defatted, then extracted, and the extract is concentrated and standardised.

What is silymarin?

Silymarin is the name for a group of natural compounds in milk thistle seeds called flavonolignans. The main ones are:

• Silybin (also spelled silibinin), usually the largest part
• Isosilybin
• Silychristin
• Silydianin

Silymarin and silybin are therefore not the same thing: silybin is one part of silymarin.

What "standardised to 80% silymarin" means

It means 80% of the extract weight is silymarin. In a 300 mg capsule, that is 240 mg of silymarin. The standardisation figure is the most useful number when comparing milk thistle products, because whole seed powder contains far less silymarin than a concentrated extract.

Our Milk Thistle capsules

Our Milk Thistle 300mg Vegan Capsules contain:

• 300 mg milk thistle extract (Silybum marianum) per capsule
• Standardised to 80% silymarin, with isosilybin approx. 2.5%, silychristin approx. 10% and silydianin approx. 7.5% as declared on the label
• Vegan HPMC capsule, no fillers or binders, made in the UK
• Suggested use: 1 to 2 capsules daily with a large glass of water
• Packs of 60, 120 and 180 capsules

You can compare it with our other single-herb products in the Herbal Singles collection.

How people take milk thistle

• Follow the serving on your label and do not exceed the recommended daily dose.
• Take it with a large glass of water, at a consistent time of day.
• Check whether milk thistle also appears in any blend you take, so you do not double up.

Who should not take milk thistle, or check first

• Daisy family allergy. Do not take it if you are allergic to plants in the daisy family, such as ragweed, chrysanthemums, marigolds or daisies.
• Pregnancy and breastfeeding. Not suitable.
• Under 18. Our products are not intended for anyone under 18.
• Medication. Speak to your doctor or pharmacist first if you take medicines for blood sugar or any prescription medicine, because milk thistle may affect how some medicines are processed.
• Hormone-sensitive conditions. Speak to your doctor first.
• Liver. If you have any concern about your liver, speak to your GP. A food supplement is not a substitute for medical advice.

Frequently asked questions

Is silymarin the same as milk thistle?

No. Milk thistle is the plant. Silymarin is a group of compounds found in its seeds, and it is what extracts are standardised to.

Is milk thistle the same as the thistles in my garden?

No. Many plants are called thistles. Milk thistle is a specific species, recognisable by its white-veined leaves.

Does milk thistle have an authorised health claim?

No. No health claims are authorised for milk thistle in Great Britain, which is why we describe our product by what is in it.

Is milk thistle vegan?

The plant is. Our capsules use plant-derived HPMC shells and are suitable for vegans.

This article is general information and is not medical advice. Food supplements should not replace a varied, balanced diet and a healthy lifestyle.