Milk Thistle
HerbalAlso called · 7 names▾▴
Mary thistle, Holy thistle, Silybum marianum, Carduus marianus, Silymarin, Silibinin, Silybin
Herbal supplement (liver health and milk supply)
Herbs and supplements are not FDA-approved before sale. About these sources
- Other
Research strength: 1 / 5
According to NCCIH, little is known about milk thistle use during pregnancy. The EMA herbal monograph says pregnancy use is not recommended because data are insufficient. Farmer et al. (2014) found a prolactin rise in pigs but no benefit to mammary development; Barbosa et al. (2020) reported some adult behavior differences in mice. These animal studies cannot establish human outcomes. NCCIH and EMA provide no trimester-specific findings. Ask your provider about your situation.
Last reviewed: 2026-10-14
Research strength: 1 / 5
According to NCCIH, little is known about milk thistle use during pregnancy. The EMA herbal monograph says pregnancy use is not recommended because data are insufficient. Farmer et al. (2014) found a prolactin rise in pigs but no benefit to mammary development; Barbosa et al. (2020) reported some adult behavior differences in mice. These animal studies cannot establish human outcomes. NCCIH and EMA provide no trimester-specific findings. Ask your provider about your situation.
Last reviewed: 2026-10-14
Research strength: 1 / 5
According to NCCIH, little is known about milk thistle use during pregnancy. The EMA herbal monograph says pregnancy use is not recommended because data are insufficient. Farmer et al. (2014) found a prolactin rise in pigs but no benefit to mammary development; Barbosa et al. (2020) reported some adult behavior differences in mice. These animal studies cannot establish human outcomes. NCCIH and EMA provide no trimester-specific findings. Ask your provider about your situation.
Last reviewed: 2026-10-14
Milk Thistle — Breastfeeding
Research strength: 3 / 5
LactMed reports limited milk-level studies and says milk thistle is unlikely to harm a breastfed infant; the EMA says use during breastfeeding is not recommended because data are insufficient. Peila et al. (2015) studied 50 mothers of preterm infants and reported no adverse events in mothers or infants, with no silymarin detected in tested milk; LactMed notes that long-term infant outcomes are not known. LactMed says milk thistle is traditionally promoted to increase supply, but trials tested concentrated extracts or mixtures, not ordinary food amounts. A 2026 review found low-certainty day-7 evidence for a silymarin, phosphatidylserine, and goat's rue mixture, but very-low-certainty evidence did not show increased volume with micronized silymarin alone at day 28. Barbosa et al. (2020) reported no early developmental differences in mice exposed during pregnancy and breastfeeding, but some adult behavioral differences; this animal study cannot establish human infant effects. Sources disagree on whether use during breastfeeding should be avoided. Ask your provider about your situation.
Last reviewed: 2026-10-14
Sources
- LactMed: Milk ThistleUS government
- EMA: EU herbal monograph on Silybum marianum fruitEU agencyEuropean guidance
- Peila et al., Pediatric Medicine and Surgery 2015US government
- Cragg et al., European Journal of Clinical Nutrition 2026US government
- ABM Clinical Protocol #9: Galactogogues, second revision 2018Professional society
- Barbosa et al., Neurotoxicology 2020US government
Pregnancy
NCCIH says little is known about milk thistle during pregnancy, and MotherToBaby says most herbal products have not been well studied. The EMA's EU herbal monograph says pregnancy use is not recommended because sufficient data are lacking; an EMA review adopted in 2024 found no new scientific data that would trigger a monograph revision. The animal study described in the live entry was Farmer et al. (2014): 33 gestating gilts, 16 controls and 17 treated, received 4 g of silymarin twice daily from gestation day 90 through day 110. Prolactin increased, but the authors concluded that the increase did not produce a beneficial effect on mammary development in late gestation; progesterone and estradiol did not change. This pig study cannot establish effects in people or trimester-specific outcomes. Barbosa et al. (2020) also studied silymarin during pregnancy and lactation in mice. The abstract reports no differences in early sensory-motor development but some adult behavior differences; it cannot establish human fetal outcomes.
Breastfeeding
LactMed reports that five mothers who had stopped nursing because their infants were 9 months old took 600 mg micronized silymarin three times daily for 5 days; milk was collected at unspecified times, and flavonolignans were below 1 mcg/L, though the assay might not detect conjugated forms. LactMed also reports that metabolites were not detected in milk from 25 women on day 14 of treatment with micronized silymarin 252 mg twice daily. Peila et al. (2015) enrolled 50 mothers at 10±1 days postpartum after delivery of infants before 32 weeks; the study abstract reports no maternal or infant adverse events and no detectable silymarin or metabolites in tested milk. The full-text page reports financial support from the product manufacturer, Milte Italia S.r.l.; the 2026 Cragg review also notes that long-term infant outcomes were not measured. For milk supply, Di Pierro et al. (2008) studied 50 mothers given 420 mg/day micronized silymarin for 63 days and reported milk-volume increases of 85.94% versus 32.09% with placebo; LactMed notes nonrandom allocation, no investigator blinding, and no follow-up of breastfeeding duration or long-term infant growth. In a 2016 randomized trial, 100 mothers of preterm infants received either 5 g/day of a silymarin-phosphatidylserine-goat's rue mixture or placebo. The 2026 Cragg review found low-certainty evidence of a 105 mL difference in milk volume by day 7 for that mixture, but very-low-certainty evidence did not show increased milk volume with micronized silymarin alone at day 28 in one study of 48 participants. Barbosa et al. (2020) studied silymarin during pregnancy and breastfeeding in mice; it reported no early sensory-motor differences but some differences in adult behavior. This animal study cannot establish human infant effects. These products and findings do not establish that ordinary milk thistle food or tea increases milk supply.
NCCIH says milk thistle extract's main constituent is silymarin, a mixture of compounds. LactMed identifies silibinin, also called silybin, as the main component of silymarin. MotherToBaby distinguishes herbs used in food from herbal products and says herbs used in food in moderation are not expected to be of concern; this is general guidance, not a milk-thistle-specific dose finding. The clinical studies tested standardized silymarin extracts or combination products, not ordinary food amounts or every product sold as milk thistle.
What was tested
Pregnancy evidence: Farmer et al. (2014) tested silymarin in 33 gestating pigs, 16 controls and 17 treated, at 4 g twice daily from gestation days 90 to 110. Breastfeeding evidence: milk-level reports included five mothers taking 600 mg three times daily for 5 days and 25 women taking 252 mg twice daily, as summarized by LactMed. Peila et al. (2015) enrolled 50 mothers of infants born before 32 weeks; its abstract does not state the dose. Di Pierro et al. (2008) tested micronized silymarin 420 mg/day for 63 days in 50 mothers; LactMed notes the groups were not randomized and investigators were not blinded. Zecca et al. (2016) tested a 5 g/day mixture of silymarin, phosphatidylserine, and goat's rue against placebo in 100 mothers of preterm infants. The Cragg et al. (2026) systematic review included 10 trials of different herbal products in mothers of preterm babies; milk-volume results for silymarin were low or very low certainty. Barbosa et al. (2020) studied silymarin exposure during pregnancy and lactation in mice. ABM Protocol #9 lists milk-thistle seed tea as anecdotal and does not recommend a specific galactagogue. Ordinary food amounts and tea have not been shown to match these concentrated product trials.
Breastfeeding use and possible infant effects through milk
- Source A says
- LactMed says limited data found no measurable silymarin components in milk and, because oral absorption is poor, milk thistle is unlikely to adversely affect the breastfed infant. Peila et al. (2015) reported no adverse events in mothers or infants and no detectable silymarin or metabolites in tested milk. (LactMed: Milk Thistle, Peila et al., Pediatric Medicine and Surgery 2015)
- Source B says
- The EMA herbal monograph says use during breastfeeding is not recommended because sufficient data are lacking. NCCIH says little is known about breastfeeding use. (EMA: EU herbal monograph on Silybum marianum fruit, NCCIH: Milk Thistle)
- Why they differ
- LactMed weighs small milk-level studies and short-term infant reports. The EMA monograph uses a conservative regulatory standard when clinical data are insufficient. The EMA statement is precautionary and does not report established infant harm.
- Other sources
- ABM cannot recommend a specific galactagogue, and the Cochrane review describes natural galactagogue results as very uncertain with limited reporting of adverse effects. (ABM Clinical Protocol #9: Galactogogues, second revision 2018, Cochrane: Oral galactagogues for mothers of term infants)
- What the evidence shows overall
- Peila et al. (2015) studied a small group of mothers of preterm infants; the article page reports manufacturer financial support, and the study did not establish long-term infant outcomes. LactMed and the 2026 review describe different preparations and outcomes, while EMA's position reflects the lack of sufficient data. The evidence supports only a limited interpretation. The proposed breastfeeding rating is guidance, with 3 research stars rather than the live 2, pending a decision.
- ABM advises evaluating possible medical causes of low milk supply and improving effective milk removal before considering a galactagogue. ABM says it cannot recommend a specific galactagogue. (Academy of Breastfeeding Medicine)
- MotherToBaby says herbs used in food in moderation are not expected to be of concern. Its fact sheet is general herbal-product guidance and does not establish a milk-thistle supplement dose. (MotherToBaby)
General research, not specific to pregnancy.
NCCIH reports digestive symptoms and product-quality concerns for some milk thistle supplements. LactMed also lists mild side effects, possible medicine interactions, and rare severe allergies.
- NCCIH lists bloating, nausea, and gas as common side effects. LactMed lists diarrhea, headache, and skin reactions, and reports rare severe allergies. (NCCIH: Milk Thistle, LactMed: Milk Thistle)
- NCCIH says some supplements have contained silymarin amounts that differ substantially from their labels or contaminants such as pesticides, microorganisms, or mycotoxins. (NCCIH: Milk Thistle)
- LactMed says milk thistle might increase the metabolism of some medicines; NCCIH says some herbs and medicines interact. (LactMed: Milk Thistle, NCCIH: Milk Thistle)
- LactMed: Milk ThistleUS governmentSecondaryPage dated 2026-03-15
- NCCIH: Milk ThistleUS governmentSecondary
- MotherToBaby: Herbal ProductsTeratology serviceSecondaryPage dated 2025-04-01Independent check
- EMA: EU herbal monograph on Silybum marianum fruitEU agencySecondaryPage dated 2018-06-05Independent checkEuropean guidance
- EMA HMPC: Addendum to assessment report on Silybum marianumEU agencySecondaryPage dated 2024-01-31Independent checkEuropean guidance
- Farmer et al., Journal of Animal Science 2014US governmentPrimaryIndependent check
- Barbosa et al., Neurotoxicology 2020US governmentPrimary
- Peila et al., Pediatric Medicine and Surgery 2015US governmentPrimaryIndependent check
- Di Pierro et al., Acta Biomedica 2008US governmentPrimaryIndependent check
- Zecca et al., European Journal of Clinical Nutrition 2016US governmentPrimaryIndependent check
- Cragg et al., European Journal of Clinical Nutrition 2026US governmentPrimaryIndependent check
- ABM Clinical Protocol #9: Galactogogues, second revision 2018Professional societySecondaryIndependent check
- Cochrane: Oral galactagogues for mothers of term infantsResearch reviewPrimaryIndependent check
Last reviewed 2026-10-14
Independent check 2026-10-14
Not yet clinician-reviewed
Ask your provider about your situation.