Research studies conducted in the laboratory have investigated the properties of silymarin or its isomer silybin using cell lines and animal models. Other substances in milk thistle have not been extensively studied.
Several research studies have investigated the effects of silymarin or silybin in a noncancer context. These studies have tested silymarin or silybin:
Coenzyme Q 10 is a compound that is made naturally in the body. The body uses it for cell growth and to protect cells from damage that could lead to cancer (see Question 1).
Animal studies have shown that coenzyme Q10 helps the immune system work better and makes the body better able to resist certain infections and types of cancer (see Question 5).
Clinical trials have shown that coenzyme Q10 helps protect the heart from the damaging side effects of doxorubicin, a drug used to treat cancer...
Silymarin or silybin has also been investigated in cancer models. The effects of silymarin and/or silybin have been investigated in prostate (DU 145, LNCaP, PC-3),[1,2,3,4,5,6]breast (MDA-MB 468, MCF-7),[7,8,9]hepatic (HepG2),[10,11] epidermoid (A431),colon (Caco-2),ovarian (OVCA 433, A2780),histiocytic lymphoma (U-937), and leukemia (HL-60) [15,16]cells. In animal tumor models, tonguecancer, skin cancer,[18,19,20,21,22,23]bladder cancer, and adenocarcinoma of the colon [25,26] and small intestine  have been investigated. These studies have tested the ability of silymarin or silibinin to:
Mitigate the toxicity associated with chemotherapy agents.
Enhance the efficacy of chemotherapy agents.
Inhibit the growth of cancer cell lines and inhibit tumor initiation or tumor promotion.
Although many of these studies have produced encouraging results, none of the findings have been replicated in human clinical trials.
Laboratory data suggest that silymarin and silybin protect the liver from damage induced by toxic chemicals. Animal studies have found that liver cells treated with silybin and then exposed to toxins do not incur cell damage or death at the same rate as liver cells that are not treated with silybin. This finding suggests that silybin can prevent toxins from entering the cell or effectively exports toxins out of the cell before damage ensues.[11,27,28,29,30,31] Alternatively, this may be related to the effect of silymarin on detoxification systems. In vitro data have shown silybin to stimulate and/or inhibit phase I detoxification pathways in silybin-treated human liver cells. However, this effect was found to be dose-dependent, and these levels are not physiologically attainable with the current manufacturer dose recommendations.[32,33]