milk thistle

Milk thistle is a tall plant with large purple flowers, native to Europe. Its extract's main constituent is silymarin, a mixture of plant compounds derived from the seeds. It is marketed as a dietary supplement, typically as capsules, tablets, or liquid extracts.

NCCIH states there isn't enough high-quality evidence to allow definite conclusions about the effects of milk thistle on health conditions in people. For liver diseases such as hepatitis B and C, non-alcoholic fatty liver disease, and alcohol-related liver disease, the research is conflicting or too limited to support conclusions. Notably, two NCCIH-funded studies, one on hepatitis C and one on non-alcoholic steatohepatitis (a progressive form of fatty liver disease), did not show benefits from the milk thistle extract silymarin. A small number of studies in people suggest milk thistle extracts may help control blood sugar in people with type 2 diabetes, but this evidence is limited and not sufficient to establish a benefit. Milk thistle is not proven to treat or cure any condition.

No standard dose has been established, and supplement products vary widely. NCCIH notes that some products have been found to contain amounts of silymarin substantially different from what is stated on the label. Because milk thistle is not proven to treat any condition and product quality varies, it is best to talk with a doctor or pharmacist before starting it, particularly if you have a health condition or take other medicines.

Taken orally, milk thistle is generally reported to be well tolerated. It may trigger allergic reactions, especially in people allergic to related plants in the daisy family, including ragweed, chrysanthemum, marigold, and daisy. Little is known about whether milk thistle is safe during pregnancy or while breastfeeding, so caution is advised in those situations. Product quality can also be a concern: beyond mislabeled silymarin content, some products have been found contaminated with pesticides, microorganisms, or mycotoxins (harmful substances produced by molds or other fungi).

The most commonly reported side effects involve the digestive system, such as bloating, nausea, and gas. Allergic reactions can also occur, particularly in people who are sensitive to ragweed and other plants in the daisy family.

NCCIH cautions that some herbs and medicines can interact in harmful ways, so anyone taking any kind of medication should consult their health care provider before using milk thistle or other herbal products. Because milk thistle may affect blood sugar, people with type 2 diabetes who take blood-sugar-lowering medication should be especially careful and discuss use with a clinician.