Written by Julia Green, Alexander Kalisch and the CAM-Cancer Consortium.
Updated January 29, 2015

Milk thistle (Silybum marianum)

Does it work?

Systematic reviews, meta-analyses

Systematic reviews of the effectiveness of milk thistle have been published but are limited to its use in the treatment of liver disorders, and on pharmacokinetics 17,29.

Narrative reviews

A narrative review of milk thistle published in 2007 summarises clinical trials on pharmacokinetics, liver diseases and cancer: the studies are included below under either clinical trials or safety if they were investigating pharmacokinetics 30.

Clinical trials

In a randomised double blind placebo controlled trial of fifty children with acute lymphoblastic leukaemia (ALL) with hepatic toxicity, receiving chemotherapy, oral milk thistle administration, at 5.1mg/kg/day for 28 days was reported to result in a trend towards a reduction of hepatic toxicity at 56 days: (liver enzymes aspartate transaminase (AST) were significantly reduced, with alanine transaminase (ALT) showing a trend towards reduction) 31. In this multi-centred pilot trial, groups were well matched and all participants accounted for. The placebo was indistinguishable from milk thistle in appearance and odour.

Small trials using combination products including milk thistle have produced contradictory results on PSA levels in prostate cancer patients 32,33. One study investigated a combination cream including milk thistle as an adjunct to radiotherapy 34. Because these trials were of combination products, it is not possible to evaluate milk thistle’s individual action in these trials.

No studies were found investigating the effect of the chemo-preventive properties of milk thistle extract on humans.

Despite great scientific interest in the chemo-preventive and therapeutic actions of milk thistle extract in oncology, the number of clinical trials is very small. Currently the clinical evidence supporting milk thistle’s use in cancer is scant.

Pre-clinical studies

In animal experiments and in vitro studies an anti-carcinogenic effect was seen for skin cancer, breast cancer, lung cancer, colon cancer, urinary bladder cancer, prostate cancer, ovarian cancer, leukaemia and cervical cancer 3,20. In in-vitro studies a synergistic action with different chemotherapeutic agents has been seen 3,21,22. Tests of in vitro effects of silibin on the chemotherapeutic agents vincristine and L-asparaginase on an experimental acute lymphoblastic leukaemia cell line showed no inhibition of their chemotherapeutic effects at low concentrations and a synergistic effect at higher concentrations with vincristine but not L-asparaginase 31. In an animal experiment with nude mice exposed to UV-B rays topical cutaneous application of silymarin was investigated in skin carcinogenesis. A reduction in skin cancer incidence was seen 20.

Citation Julia Green, Alexander Kalisch, CAM-Cancer Consortium. Milk thistle (Silybum marianum) [online document]. http://ws.cam-cancer.org/The-Summaries/Herbal-products/Milk-thistle-Silybum-marianum. January 29, 2015.

References

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