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Additional recommended knowledge
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.
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.
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.
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. 
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 while studies which used significantly larger doses concluded that silymarin was biologically active and had theraputic effects.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Milk_thistle". A list of authors is available in Wikipedia.|