Brewer's Yeast
Other supplementAlso called · 5 names▾▴
brewers yeast, brewer yeast, brewer’s yeast, Saccharomyces cerevisiae, beer yeast
Dietary supplement (milk supply)
Herbs and supplements are not FDA-approved before sale. About these sources
- Other
Research strength: 1 / 5
The sources reviewed did not include a brewer's-yeast-specific pregnancy study or recommendation. MotherToBaby's fact sheet covers herbal products generally and says many have not been evaluated in pregnancy; it does not discuss brewer's yeast. LactMed describes brewer's yeast for milk supply, but its record covers breastfeeding rather than pregnancy. These sources do not establish pregnancy effects. Evidence for the first trimester remains insufficient. Ask your provider about your situation.
Last reviewed: 2026-10-14
Research strength: 1 / 5
The sources reviewed did not include a brewer's-yeast-specific pregnancy study or recommendation. MotherToBaby's fact sheet covers herbal products generally and says many have not been evaluated in pregnancy; it does not discuss brewer's yeast. LactMed describes brewer's yeast for milk supply, but its record covers breastfeeding rather than pregnancy. These sources do not establish pregnancy effects. Evidence for the second trimester remains insufficient. Ask your provider about your situation.
Last reviewed: 2026-10-14
Research strength: 1 / 5
The sources reviewed did not include a brewer's-yeast-specific pregnancy study or recommendation. MotherToBaby's fact sheet covers herbal products generally and says many have not been evaluated in pregnancy; it does not discuss brewer's yeast. LactMed describes brewer's yeast for milk supply, but its record covers breastfeeding rather than pregnancy. These sources do not establish pregnancy effects. Evidence for the third trimester remains insufficient. Ask your provider about your situation.
Last reviewed: 2026-10-14
Brewer's Yeast — Breastfeeding
Research strength: 3 / 5
LactMed describes brewer's yeast as a supplement used to try to increase milk production, notes that product content varies, and reports mostly gastrointestinal side effects among nursing mothers. In a 2025 randomized trial, women taking 5 g/day of molasses-grown yeast for four weeks were more likely than placebo participants to perceive an increase in milk production (65% vs 35%), but the trial did not measure total milk volume. A 2026 randomized trial in mothers who gave birth before 34 weeks measured expressed milk and found no clear short-term effect, though the small sample could not rule out a clinically meaningful benefit. LactMed reports no published maternal or infant level data; the effect on milk volume and nursing infants remains uncertain. Ask your provider about your situation.
Last reviewed: 2026-10-14
Sources
- LactMed: Brewer’s YeastUS government
- McBride et al., Use and experiences of galactagogues while breastfeeding among Australian womenUS government
- Jia et al., Saccharomyces cerevisiae Yeast-Based Supplement and Breast Milk Supply (2025 RCT)
- Grzeskowiak et al., BLOOM randomized trialUS government
Pregnancy
Pregnancy-specific studies or recommendations for brewer's yeast were not located in the reviewed sources. MotherToBaby's fact sheet is about herbal products generally and does not discuss Saccharomyces cerevisiae, so it supports only the general point that many supplements have not been evaluated in pregnancy. LactMed is a lactation database and does not assess pregnancy outcomes for this item. No claim about miscarriage or birth defects is made; evidence remains insufficient for all trimesters.
Breastfeeding
In the 2021 Australian cross-sectional survey, 592 women reported using brewer's yeast; 65 (11%) reported at least one side effect and 12 (2%) reported more than one. The survey collected self-reported use and perceptions, not direct milk-volume measurements. The 2025 randomized trial tested 5 g/day of powdered brewer's yeast grown on molasses for four weeks among breastfeeding women with healthy singleton infants aged 1 to 7 months. Its abstract reports 68 women randomized, while the full text says 72 signed up and 68 completed; 65% of the yeast group versus 35% of placebo participants perceived an increase in milk production, but total milk volume was not measured. The 2026 BLOOM randomized trial enrolled 105 mothers who delivered before 34 weeks and compared brewer's yeast, beta-glucan, and placebo capsules for seven days; the adjusted yeast-placebo difference in daily expressed milk was +94 mL (95% CI -51 to 239), and authors found no clear effect but could not rule out a clinically meaningful benefit. LactMed reports that published maternal and infant level data were not found; the trials measured milk composition, maternal perceptions, or expressed volume, not yeast levels in milk or infant blood.
Brewer's yeast is an inactive form of Saccharomyces cerevisiae sold as a dietary supplement. A 2021 review describes tablets, powders, flakes, and liquids made from different sources, including brewing or fermentation and molasses; nutrient content can vary. The 2025 trial used powder grown on molasses, so its findings do not necessarily apply to products made from brewing. The trial did not report a tyramine assay for its test powder.
What was tested
Older human information was mainly surveys of use and self-reported perceptions, not milk-volume measurements. A 2025 randomized trial used 5 g/day of molasses-grown powder for four weeks and assessed milk oligosaccharides, perceptions, and other outcomes, but not total milk volume. The 2020 Cochrane review lists the same registration, ACTRN12619000704190, as an ongoing yeast-powder study with 40 estimated participants, nine capsules daily, and a stated 5 g per capsule for 28 days; the 2025 paper reports nine capsules containing 5 g/day total. The underlying registry record or any dose amendment was not verified, so the difference is unresolved. The 2026 BLOOM trial tested yeast, beta-glucan, or placebo capsules for seven days in mothers after births before 34 weeks and measured expressed milk volume on day 7.
What do human trials show about brewer's yeast and milk production?
- Source A says
- LactMed says no scientifically valid human studies have established an effect on milk supply, and its account of BLOOM reports no meaningful difference in milk output. (LactMed: Brewer’s Yeast)
- Source B says
- The 2025 randomized trial found that more participants taking molasses-grown yeast perceived an increase in milk production than placebo participants, but it did not measure total milk volume. The 2026 BLOOM trial found no clear short-term effect on expressed milk, while its confidence interval did not rule out a clinically meaningful benefit. (Jia et al., Saccharomyces cerevisiae Yeast-Based Supplement and Breast Milk Supply: A Randomised Placebo-Controlled Trial, Grzeskowiak et al., Effect of brewers' yeast or beta-glucan on breast milk supply following preterm birth: the BLOOM randomized trial)
- Why they differ
- The 2025 trial measured maternal perceptions and milk oligosaccharides in women with infants aged 1 to 7 months; BLOOM measured expressed milk for seven days in mothers after preterm birth. The populations, product preparations, duration, and endpoints differ, and both trials were small.
- Other sources
- ABM says current data are insufficient for definitive galactagogue recommendations. Cochrane says causes of low milk production should first be identified and corrected; its 2020 review lists this yeast trial registration as ongoing, not as an efficacy result. (Academy of Breastfeeding Medicine Clinical Protocol #9: Use of Galactogogues (Second Revision), Cochrane review: Oral galactagogues for increasing breast milk production in mothers of non-hospitalised term infants)
- What the evidence shows overall
- The evidence does not establish whether brewer's yeast increases milk volume. The 2025 trial found a difference in perception, not measured volume. BLOOM found no clear short-term effect, but its small sample could not rule out a meaningful increase. Keep the rating insufficient.
Does a tranylcypromine tyramine warning apply to brewer's yeast supplements?
- Source A says
- The 2025 trial excluded users of monoamine oxidase inhibitor medicines because the authors said SCYS may contain large amounts of tyramine. (Jia et al., Saccharomyces cerevisiae Yeast-Based Supplement and Breast Milk Supply: A Randomised Placebo-Controlled Trial)
- Source B says
- The tranylcypromine label lists concentrated yeast extract among foods high in tyramine, but lists brewer's yeast among foods with no or little tyramine. (DailyMed: Tranylcypromine tablets, prescribing information)
- Why they differ
- The trial raises a general concern about possible product content; the label distinguishes yeast extract from brewer's yeast for patients taking tranylcypromine. The trial did not report the tyramine content of its molasses-grown powder, and the label does not test every retail supplement.
- What the evidence shows overall
- This evidence does not support a blanket warning about all brewer's yeast products. The tyramine content of the trial product and other retail supplements remains unknown, so keep the product distinction and uncertainty explicit.
- Cochrane says every attempt should first be made to identify and correct the causes of low milk production before trying an oral milk booster. (Cochrane review: Oral galactagogues (2020))
- ABM says the feeding process should be thoroughly evaluated and milk removal maximized; it also says the current data are insufficient for definitive galactagogue recommendations. (Academy of Breastfeeding Medicine Clinical Protocol #9 (2018))
General research, not specific to pregnancy.
A 2025 trial excluded participants taking monoamine oxidase inhibitor (MAOI) medicines because the authors raised a possible tyramine concern. The tranylcypromine label separates concentrated yeast extract from brewer's yeast in its tyramine table. The test powder's tyramine content was not reported, so these sources do not establish the content of every supplement.
- Jia et al. say SCYS may contain large amounts of tyramine and excluded users of MAOI medicines. (Jia et al., Saccharomyces cerevisiae Yeast-Based Supplement and Breast Milk Supply: A Randomised Placebo-Controlled Trial)
- The tranylcypromine label lists concentrated yeast extract among tyramine-rich foods to avoid, and brewer's yeast among foods with no or little tyramine. (DailyMed: Tranylcypromine tablets, prescribing information)
- MotherToBaby: Herbal Products (general information)Teratology serviceSecondary
- LactMed: Brewer’s YeastUS governmentSecondaryPage dated 2026-09-15Independent check
- Academy of Breastfeeding Medicine Clinical Protocol #9: Use of Galactogogues (Second Revision)SecondaryIndependent check
- Cochrane review: Oral galactagogues for increasing breast milk production in mothers of non-hospitalised term infantsResearch reviewPrimaryPage dated 2020-05-18Independent check
- Jia et al., Saccharomyces cerevisiae Yeast-Based Supplementation as a Galactagogue (2021 review)US governmentPrimaryIndependent check
- McBride et al., Use and experiences of galactagogues while breastfeeding among Australian womenUS governmentPrimaryIndependent check
- Jia et al., Saccharomyces cerevisiae Yeast-Based Supplement and Breast Milk Supply: A Randomised Placebo-Controlled TrialPrimaryPage dated 2025-09-11
- Grzeskowiak et al., Effect of brewers' yeast or beta-glucan on breast milk supply following preterm birth: the BLOOM randomized trialUS governmentPrimaryPage dated 2026-09-01Independent check
- Grzeskowiak et al., BLOOM trial preprint funding disclosurePrimaryPage dated 2026-07-09
- DailyMed: Tranylcypromine tablets, prescribing informationDrug company labelTertiaryPage dated 2024-10-17Independent check
Last reviewed 2026-10-14
Independent check 2026-10-14
Not yet clinician-reviewed
Ask your provider about your situation.