Milk thistle may help to treat several health conditions, such as liver disease, diabetes, and cancer. This supplement contains silymarin, which is the medicinally active component of the plant. Although some preliminary studies have shown that milk thistle may be effective at treating some conditions, there is not enough evidence to confirm this. Although this substance is a "natural" product, side effects are still possible and may include nausea, gas, and diarrhea.
Milk thistle is a flowering plant used medicinally as an herbal supplement. Most often, the herb is claimed to be useful for treating or preventing liver diseases, although people use it for other uses as well.
(Click Milk Thistle Benefits for more information on what the supplement is used for.)
As a plant, milk thistle contains many different compounds. Of these compounds, it appears that silymarin (which is actually a mixture of four different flavonolignans) is the medicinally active component of milk thistle. Silymarin has many different effects in the body.
Silymarin may work for liver disease in several ways. It helps liver cells to regenerate and changes the outer membrane of liver cells to decrease the penetration of toxins. Silymarin may also decrease inflammation and fibrosis, and may also affect the immune system. It may also help prevent the liver from metabolizing certain substances into toxic byproducts.
In addition, silymarin appears to inhibit tumor necrosis factor (TNF), a compound that plays an important role in autoimmune diseases (such as rheumatoid arthritis or Crohn's disease) and cancer.
Silymarin also acts as an antioxidant, which may explain how milk thistle works for several different conditions, including diabetes. Because oxidative stress may damage the pancreas in people with diabetes, compounds with antioxidant activity may preserve the ability of the pancreas to produce insulin.
Certain parts of the milk thistle plant seem to have estrogenic effects, which might explain how it works for prostate cancer and various other conditions.