Milk thistle

Milk thistles are thistles of the genus Silybum Adans., flowering plants of the daisy family (Asteraceae). They are native to the Mediterranean regions of Europe, North Africa and the Middle East. Whilst health uses mostly for chronic liver disease have been traditionally claimed for the plant, increasing research is being undertaken on this and other possible medical uses.^[1]

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Description and classification

    Members of this genus grow as annual or biennial plants. The erect stem is tall, branched and furrowed but not spiny. The large, alternate leaves are waxy-lobed, toothed and thorny, as in other genera of thistle. The lower leaves are cauline (attached to the stem without petiole). The upper leaves have a clasping base. They have large, disc-shaped pink-to-purple, rarely white, solitary flower heads at the end of the stem. The flowers consist of tubular florets. The phyllaries under the flowers occur in many rows, with the outer row with spine-tipped lobes and apical spines. The fruit is a black achene with a white pappus.
Only two species are currently classified in this genus:

• Silybum eburneum Coss. & Dur., known as the Silver Milk Thistle, Elephant Thistle, or Ivory Thistle
  • Silybum eburneum Coss. & Dur. var. hispanicum
• Silybum marianum (L.) Gaertner, the Blessed Milk Thistle, which has a large number of other common names, such as Variegated Thistle.

The two species hybridise naturally, the hybrid being known as Silybum × gonzaloi Cantó , Sánchez Mata & Rivas Mart. (S. eburneum var. hispanicum x S. marianum)

A number of other plants have been classified in this genus in the past but have since been relocated elsewhere in the light of additional research.

S. marianum is by far the more widely known species. It is believed to give some remedy for liver diseases (e.g. viral hepatitis) and an extract, silymarin, is used in medicine. The adverse effect of the medicinal use of milk thistle is loose stools.

Health benefits

Milk thistle has been reported to have protective effects on the liver and to improve its function. It is typically used to treat liver cirrhosis, chronic hepatitis (liver inflammation), and gallbladder disorders. The active compound in Milk thistle is silymarin, a mixture of at least 4 closely related flavonolignans, 60% to 70% of which is a mixture of 2 diastereomers of silybin. Silymarin is typically administered in amount ranging from 200-500mg per day. Whether or not these dosages are optimal is not known; no scientific data on which to base effective dosage level guidelines is available.

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.^[1]

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."^[2]. 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. ^[3]

A review of studies of silymarin and liver disease which are available on the web shows an interesting pattern: studies which tested low dosages of silymarin concluded that silymarin was ineffective^[4] while studies which used significantly larger doses concluded that silymarin was biologically active and had theraputic effects.^[5]

Beside benefits for liver disease, 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.^[6]
• Milk thistle is also used in many products claiming to reduce the effects of a hangover.
• Milk thistle can also be found as an ingredient in some energy drinks like the AriZona Beverage Company Green Tea energy drink and Rockstar Energy Drink.

See also

• Blessed milk thistle
• Cnicus (Blessed thistle)

References

• Milk thistle (Silybum marianum (L.) Gaertn.) - information at the site of Washington State Noxious Weed Control Board
• K. Flora, M. Hahn, H. Rosen and K. Benner. Milk Thistle (Silybum marianum) for the Therapy of Liver Disease. Am. J. Gastroenterology 93, 139-143.
• Milk Thistle Summary Report - Information on uses, both historical and medical, with online discussion forum

• Hepatitis C Treatment Conclusions by various referenced studies on the potential use of milk thistle in treating Hepatitis C and other liver health issues.