Blessed thistle (Cnicus benedictus, Carduus benedictus, Cardui benedicti) contains sesquiterpene lactones, triterpenoids, lignans, tannins, essential oils, flavonoids, and polyenes. Blessed thistle is a purported galactogogue,[1-6] and is included in some proprietary mixtures promoted to increase milk supply; however, no scientifically valid clinical trials support this use. Galactogogues should never replace evaluation and counseling on modifiable factors that affect milk production.[7,8] Blessed thistle is "generally recognized as safe" (GRAS) as a flavoring in alcoholic beverages (e.g., Benedictine) by the U.S. Food and Drug Administration. Because it is a member of the ragweed family, allergy is a concern and high doses reportedly cause stomach cramps, nausea and vomiting. Elevated liver enzymes occurred in a woman taking Mother's Milk Tea, which contains blessed thistle and other ingredients.[9]
Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.