Is Milk Thistle safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Milk Thistle. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
A study compared a commercial product containing silymarin 252 mg (BIO-C) to placebo every 12 hours in mothers of preterm ( 32 weeks) infants. No adverse effects were observed in any of the infants.[ 10 ] In a study of galactogogue containing 5 grams of a mixture of silymarin, phosphatidylserine and galega (goat's rue) in an unspecified proportion and from an unspecified source, none of the typical adverse effects of silymarin were noted in the breastfed infants.[ 14 ]
Effects on milk supply
No human data are available on the effect of milk thistle or its components on serum prolactin. A study in gilts (female domestic pigs) found that silymarin 4 grams twice daily during pregnancy and lactation found that serum prolactin levels were increased compared to gilts given placebo. The slight increase in prolactin had no effect on mammary gland development, nor on plasma progesterone or estradiol.[ 15 ] A study was performed on 50 medically normal postpartum mothers with milk production judged to be less than normal for patients in the hospital in Lima, Peru where the study was conducted. Mothers were divided non-randomly into 2 groups of 25 women who had identical ages, weights, number of children and newborn's age, although ages were not reported. The group that was given micronized silymarin (BIO-C brand) 420 mg daily for 63 days had a baseline milk production of 602 mL daily. The milk volumes and composition (water, fats, carbohydrate and protein) of the 2 groups were not significantly different on day 0. The group given an identical placebo had a baseline milk production of 530 mL daily. Milk production was measured on day 30 and day 63 by infant weighing before and after nursing followed by emptying the breasts with a breast pump. The composition of the milk was also determined. Statistically significant differences in average milk production were found on day 30 (990 grams in the silymarin group and 650 grams in the placebo group) and on day 63 (1119 grams in the silymarin group and 701 grams in the placebo group). Milk composition was not different between the groups at the two time points.[ 9 ] Deficiencies in this study include the lack of randomization, no investigator blinding, and no optimization of breastfeeding technique prior to study enrollment. Also, breastfeeding duration and long-term infant growth were not studied. In a randomized, double-blind study, a placebo (5 grams of lactose) or a commercial product (Pi latte Plus, Milte) containing
Levels in milk
Silibinin has low and variable bioavailability of 23 to 47% after oral administration and is rapidly converted into glucuronide conjugates that have longer half-lives in plasma than the unconjugated forms.[ 8 ] Maternal Levels. Five mothers who had decided to stop nursing because their infants were 9 months old were given 600 mg of micronized silymarin (BIO-C brand) orally 3 times daily. After 5 days of therapy, milk was collected at unspecified times for analysis by HPLC. Silymarin flavonolignans were undetectable ( 1 mcg/L) in milk samples; however, their conjugated forms might not have been detected by the assay method used.[ 9 ] Silymarin metabolites (silychristin, silydianin, silibyn A, silibyn B, isosilybin A and isosilybin B) were not detected ( 0.3 mg/kg) in breastmilk of any of 25 women studied on day 14 of treatment with micronized silymarin 252 mg (BIO-C) twice daily.[ 10 ] Quercetin can be found in breastmilk of mothers with normal diets.[ 11 ] Milk samples from 17 nursing mothers on uncontrolled diets were taken at 1, 4 and 13 weeks postpartum at times between 10 am and 1 pm. Average quercetin levels in breastmilk were 48 nmol/L at week 1, 60 nmol/L at week 4 and 51 nmol/L at week 13. Kaempferol concentrations ranged from 7.8 to 71.4 nmol/L, increasing from weeks 1 to 13 (and from weeks 4 to 13. Because of the uncontrolled diet and varying sampling times, the range of values among individuals was large.[ 12 ] Quercetin was measured in the milk of 11 mothers after they received an onion soup that contained either 0.8 or 1 mg/kg of quercetin glucosides. A baseline milk sample was obtained after a 5-day low-quercetin diet, and 7 milk samples were obtained over the 48 hours following soup ingestion. Baseline total (from conjugated and unconjugated) quercetin in breastmilk averaged 45 nmol/L. An average peak milk quercetin level of 68 nmol/L was attained at an average of 11.9 hours after the soup meal. The average half-life of quercetin in breastmilk was 50.
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.