Is Blessed Thistle safe while breastfeeding?

Summary of use during breastfeeding

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.

Effects on the breastfed infant

A small manufacturer-sponsored, double-blind, randomized study compared Mother's Milk tea (Traditional Medicinals, Sebastopol, CA) to lemon verbena tea in exclusively breastfeeding mothers with milk insufficiency. Each Mother's Milk tea bag contained 35 mg of blessed thistle herb as well as several other herbs. Mothers were instructed to drink 3 to 5 cups of tea daily. No differences were seen between groups in infant digestive, respiratory, dermatological, and other maternal-reported adverse events. No differences were seen in the growth parameters of the breastfed infants between the two groups.[10]

Effects on milk supply

In a survey of nursing mothers in Australia, 98 mothers were taking blessed thistle as a galactogogue. On average, mothers rated blessed thistle being between “slightly effective” and “moderately effective” on a Likert scale. Eight percent of mothers taking blessed thistle reported experiencing adverse reactions, most commonly nausea, stomach cramps, dry mouth and fatigue.[11]

Levels in milk

Maternal Levels. Relevant published information was not found as of the revision date.

Infant Levels. Relevant published information was not found as of the revision date.