The milk thistle is a thistle of the genus Silybum Adans., a flowering plant of the daisy family (Asteraceae). They are native to the Mediterranean regions of Europe, North Africa and the Middle East. The name "milk thistle" derives from two features of the leaves; they are mottled with splashes of white and they contain a milky sap.
Research is being undertaken on the physiological effects, potential therapeutic properties, and possible medical uses of milk thistle.
For many centuries extracts of milk thistle have been recognized as "liver tonics." Research into the biological activity of silymarin and its possible medical uses has been conducted in many countries since the 1970s, but the quality of the research has been uneven. Milk thistle has been reported to have protective effects on the liver and to greatly improve its function. It is typically used to treat liver cirrhosis, chronic hepatitis (liver inflammation), toxin-induced liver damage including the prevention of severe liver damage from Amanita phalloides ('death cap' mushroom poisoning), and gallbladder disorders.
Reviews of the literature covering clinical studies of silymarin vary in their conclusions. A review using only studies with both double-blind and placebo protocols concluded that milk thistle and its derivatives "does not seem to significantly influence the course of patients with alcoholic and/or hepatitis B or C liver diseases." A different review of the literature, performed for the U. S. Department of Health and Human Services, found that, while there is strong evidence of legitimate medical benefits, the studies done to date are of such uneven design and quality that no firm conclusions about degrees of effectiveness for specific conditions or appropriate dosage can yet be made.
Toxin-induced liver damage
Research suggests that milk thistle extracts both prevent and repair damage to the liver from toxic chemicals and medications. Workers who had been exposed to vapors from toxic chemicals (toluene and/or xylene) for 5–20 years were given either a standardized milk thistle extract (80% silymarin) or placebo for 30 days. The workers taking the milk thistle extract showed significant improvement in liver function tests (ALT and AST) and platelet counts vs. the placebo group.
The efficacy of silymarin in preventing drug-induced liver damage in patients taking psychotropic drugs long-term has been investigated. This class of drugs is known to cause liver damage from oxidation of lipids.[clarification needed]Patients taking silymarin in the study had less hepatic damage from the oxidation of lipids than patients taking the placebo.
A clinical trial in humans showed that silymarin (140 mg orally 3 times daily) was not effective when used for 1 year in combination with ursodeoxycholic acid (UDCA) for the treatment of primary biliary cirrhosis. A study in baboons indicated that continuous intragastric infusion of silymarin retarded the development of alcohol-induced hepatic fibrosis over a 3-year period. The authors suggested that the failure of silymarin to show beneficial effects in other clinical trials may have been due to poor compliance with treatment, resulting in insufficient dosing.
Amanita mushroom poisoning
The efficacy of thirty different treatments was analyzed in a retrospective study of 205 cases of Amanita phalloides (death cap) mushroom poisoning. Both penicillin and hyperbaric oxygen independently contributed to a higher rate of survival. When silybin [silibinin] was added to the penicillin treatment, survival was increased even more. In another 18 cases of death cap poisoning, a correlation was found between the time elapsed before initiation of silybin therapy, and the severity of the poisoning. The data indicates that severe liver damage in Amanita phalloides poisoning can be prevented effectively when administration of silybin begins within 48 hours of mushroom intake. In a recent 2007 event, a family of six was treated with milk thistle and a combination of other treatments to save them from ingested poisonous mushrooms. While five of the six made a full recovery, the grandmother showed liver recovery but was overcome by kidney failure related to the poisonous mushrooms.
Beside benefits for liver disease, other unproven treatment claims include:
- Lowering cholesterol levels
- Reducing insulin resistance in people with type 2 diabetes who also have cirrhosis,
- Reducing the growth of cancer cells in breast, cervical, and prostate cancers.
- Reducing liver damaging effects of chemotherapeutic drugs
- Clinical study has shown that liver function tests can be improved in active hepatitis patients.
- silymarin may have use, potentially, in the treatment of diabetic nephropathy.