Milk thistle: benefits, dosage & side-effects


What is milk thistle and what does it do?

Milk thistle – also known as Silybum marianum – is a bright pink flowering plant that grows wild in southern Europe, northern Africa and the Middle East. Traditionally, it’s been used for more than 2000 years to support the liver and spleen.1 Nowadays, milk thistle is used as a herbal remedy to soothe indigestion and for its liver-protective effects.2 It is available as capsules, tablets or a tea.

Benefits of milk thistle

What does milk thistle do in the body?

In the 1960s, scientists extracted silymarin, a trio of active ingredients in milk thistle.3 Silymarin can protect the liver and help it to regenerate, while acting as a natural detoxifier for the liver too, according to a 2014 study published in World Journal of Hepatology.4 More research is needed to find out how exactly silymarin works inside the body, but a 2002 study published in Clinical Drug Investigation found it can:5
  • scavenge damaging free radicals
  • protect cell membranes, for example preventing toxins from entering liver cells
  • help regenerate damaged cells
  • neutralise toxins that can damage the liver, such as alcohol
Silymarin also helps reduce inflammation in cells and activates their repair, according to a 2015 study by University of Washington.6 However, other studies on milk thistle and its liver-protective effects have been mixed.7

If you’re interested in taking milk thistle, talk to your GP or a healthcare professional first.


How much milk thistle is safe to take?

The European Medicines Agency recommends taking 300mg-600mg of milk thistle, two or three times a day.8 These people should avoid taking milk thistle extract:9,10
  • pregnant or breastfeeding women – there is no data on its safety
  • people with diabetes – it may reduce blood glucose levels in people with this disease, putting you at risk of low blood sugar
  • women with breast cancer, uterine cancer, ovarian cancer, uterine fibroids or endometriosis – it’s thought milk thistle may have oestrogenic effects
  • people who are allergic to plants in the asteracea family e.g. ragweed, chrysanthemum and artichoke – there is a risk of an allergic reaction


What are the side-effects of taking milk thistle?

Side-effects aren’t common but include:11,12
  • itchiness
  • headaches
  • diarrhoea
  • nausea

Allergic reactions, including anaphylaxis, are rare but have been reported.

[Shop Remedies] 
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.


1. Milk Thistle

2. European Medicines Agency. European Union herbal monograph on Silybum marianum (L.) Gaertn., fructus 

3. As Source 1 

4. Vargas-Mendoza N, et al. Hepatoprotective effect of silymarin

5. Lovelace ES, et al. Silymarin Supresses Cellular Inflammation by Inducing Reparative Stress Signaling

6. Frashchini F, Demartini G, Esposti D. Pharmacology of Silymarin

7. Helen West. Healthline. 7 Science-Based Benefits of Milk Thistle 

8. As Source 2

9. As Source 2

10. Mayo Clinic. Milk Thistle

11. As Source 6

12. As Source 11

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