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Cancer Health Center

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Milk Thistle (PDQ®): Complementary and alternative medicine - Health Professional Information [NCI] - General Information

The botanical name for milk thistle is Silybum marianum (L.) Gaertn. Milk thistle is also referred to as holy thistle, Marian thistle, Mary thistle, Our Lady's thistle, St. Mary thistle, wild artichoke, Mariendistel (German), and Chardon-Marie (French). The plant is indigenous to Europe but can also be found in the United States and South America. Traditionally, the leaves have been used in salads, and the fruit of the flower has been roasted as a coffee substitute. The seeds of milk thistle are the medicinal parts of the plant.[1] The primary active constituent of milk thistle is silymarin, which is composed of the following isomers: silybin (consisting of silybins A and B), isosilybin (consisting of isosilybins A and B), silychristin, and silydianin. Most supplements are standardized according to their silybin content. Silybin and isosilybin are both mixtures of two diastereomers, silybins A and B and isosilybins A and B, respectively.[2,3] Special formulations of silybin have been developed to enhance the bioavailability of the herbal product; these forms are sold under the names Legalon, silipide, and Siliphos. Because of milk thistle's lipophilic nature, it is usually administered in capsule or tablet form rather than as an herbal tea. In Europe, silybin is administered intravenously as the only effective antidote for Amanita phalloides (Fr.) Link toxin.[4] Humans exposed to this mushroom toxin develop serious liver failure that ultimately progresses to death.

Several companies distribute milk thistle as a dietary supplement. In the United States, dietary supplements are regulated as foods, not drugs. Therefore, premarket evaluation and approval by the Food and Drug Administration (FDA) are not required unless specific disease prevention or treatment claims are made. Because dietary supplements are not formally reviewed for manufacturing consistency, ingredients may vary considerably from lot to lot; in addition, there is no guarantee that ingredients identified on product labels are present at all or are present in the specified amounts. It is important to note that the FDA has not approved the use of milk thistle as a treatment for cancer patients or patients with any other medical condition.

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