Herbs & Supplements

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Uses

Milk thistle contains several chemicals with possible medical effects. Most current research focuses on a mixture of them, collectively called silymarin, which may have specific protective effects on cells in the liver. In multiple human, animal, and laboratory studies, silymarin has shown differing degrees of effectiveness for protecting the liver from damage caused by alcohol, chemicals, drugs, diseases, and poisonous plants. It is used to treat both acute conditions (such as poisoning) and long-term diseases (such as hepatitis C). Silymarin and other chemicals in milk thistle are believed to protect liver cells in several different ways:

Silymarin has antioxidant properties. Oxidation is a natural process necessary to convert foods into components the body can use, but it also produces by-products known as oxygen free radicals, which may damage body cells. Antioxidants are thought to prevent or lessen damage.

Anti-inflammatory effects of silymarin help keep liver cells from swelling after being injured.

Silymarin seems to encourage the liver to grow new cells, while discouraging the formation of inactive fibrous tissue.

By changing the outside layer of liver cells, silymarin actually may keep certain harmful chemicals from getting into liver cells.

Milk thistle may also cause the immune system to be more active.

Silymarin has also been tested in multiple laboratory studies involving various types of human cancer cells. In general, chemicals in silymarin seem to interrupt cancer cell division, keep cancer cells from spreading, and shorten the time that cancer cells live. They may also stop or limit the formation of new blood vessels that supply tumors. Because silymarin attaches to places in cells where the sex hormones androgen and estrogen usually stick, most earlier research centered on hormone-dependent cancers, such as breast cancer and prostate cancer. Due to possible estrogen-like effects of milk thistle, however, certain types of breast cancer tumors actually increased in number and/or seriousness when milk thistle was given to female animals with existing breast tumors. Milk thistle has also been tested for treating other cancers such as leukemia. In addition, some chemicals from milk thistle may increase the effectiveness of current anticancer drugs or reduce the toxicity that some drugs cause to non-cancerous cells. Some of these anticancer effects are being studied in human trials, but none is confirmed, yet.

The application of one silymarin component, silibinin, to the skin of laboratory animals has protected the animals against the development of skin cancer--either before or immediately after exposure to damaging radiation. Silibinin may even help to restore damaged skin somewhat by mending DNA that has been harmed by ultraviolet (UV) rays. In a separate animal study, both topical and oral silymarin helped lessen the systemic effects of burns on the skin.

Milk thistle and chemicals derived from it are being studied for a number of additional possible effects. For example, in animal studies and one small study of humans, milk thistle produced modest reductions in cholesterol levels. A growing amount of information from laboratory, animal, and human studies suggests that milk thistle helps to lower blood sugar levels. Apparently, it works by making the body use insulin better and not by affecting the body's production of insulin. Results of separate laboratory studies show that milk thistle may help to protect the heart muscle from damage caused by certain drugs. However, these potential uses have not been well studied in humans nor have they been proved in animal or laboratories studies.