What is milk thistle – and does it have any health benefits?

29th March, 2021 • 4 min read

Historically, people have used milk thistle to treat liver and gallbladder problems. It’s also used as a supplement to help with conditions like hepatitis, cirrhosis, jaundice, diabetes and indigestion.

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But how effective is milk thistle really, and is there enough evidence to back up its health claims?

What is milk thistle?

Milk thistle is a flowering plant from the same plant family as daisy and ragweed. It has purple flowers and white veins, and the stem and leaves of the plant are sometimes eaten in salads.

The seeds of milk thistle and the parts of the plant that live above the ground can be used to make a type of herbal remedy called milk thistle extract. This extract is high in a group of plant compounds known as silymarin, which is reported to have antioxidant and anti-inflammatory properties.

What are the possible benefits of milk thistle?

Some research suggests milk thistle might be helpful with the following:

Liver damage and disease

The silymarin found in milk thistle may protect liver cells from damage caused by toxic chemicals and drugs.

The evidence on whether taking milk thistle can help with liver disease in people who drink alcohol is conflicting, and more research needs to be done into this potential benefit.


Research suggests that milk thistle can improve diabetes when taken along with diabetes medication. There is some evidence that milk thistle can help lower blood sugar levels in people with type 2 diabetes, but there isn’t enough evidence to draw definite conclusions about its effectiveness.

Side effects of cancer treatment

A small number of studies have investigated how silymarin might reduce the side effects of cancer treatment. The findings suggest that silymarin may:

  • reduce liver damage caused by chemotherapy in children with acute lymphoblastic leukaemia
  • reduce mucositis (painful inflammation of the digestive tract) caused by radiation in patients with head and neck cancer
  • prevent skin rashes (when used as a cream) in people with breast cancer who have had radiation therapy

How much milk thistle should you take?

There is no defined milk thistle dosage, as this varies from product to product and depends on things like the quality of the supplement and the active ingredients used to make it.

Ask your doctor or pharmacist for advice on how to use milk thistle – and always follow the dosage instructions.

What are the risks and side effects of taking milk thistle?

Milk thistle seems to have few side effects, but some people may experience:

  • nausea
  • diarrhoea
  • skin itching
  • bloating
  • fullness
  • loss of appetite
  • headache

If you decide to take milk thistle, there are some important things to be aware of:

  • milk thistle can cause allergic reactions, especially if you’re allergic to plants in the same family, like ragweed, chrysanthemum, marigold and daisy
  • it’s unknown if milk thistle is safe if you’re pregnant or breastfeeding, so ask your doctor before using it if you’re pregnant or breastfeeding
  • milk thistle is not recommended for children
  • milk thistle can interact with some medications including those for high cholesterol (statins), oestrogen medication or pills and other medications – speak to your doctor if you’re taking medication
  • milk thistle can act like oestrogen in the body – if you have or are at risk of a hormone-related condition, including breast cancer, uterine cancer, ovarian cancer, endometriosis or uterine fibroids, speak to your doctor before using milk thistle

Key points

  • milk thistle is a plant that’s traditionally been used to treat liver and gallbladder problems
  • the group of plant compounds found in milk thistle is known as silymarin
  • some research suggests silymarin may be helpful in treating diabetes and liver disease
  • silymarin may help reduce the side effects of some cancer treatment
  • milk thistle can interact with some medications – speak to your doctor if you’re unsure about taking milk thistle

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.