Brewer's Yeast (Inactive)

Also called brewer's yeast, brewers yeast, debittered brewer's yeast, inactive yeast, Saccharomyces cerevisiae (inactive).

Best grade D across 5 graded outcomes Other Last checked

The short answer

From 8 sources

Brewer's yeast is inactive Saccharomyces cerevisiae, widely used to try to raise breast milk supply. In 105 mothers of preterm babies, it did not clearly change milk output, and lactation cookies containing it did no better than plain cookies. One 84-person trial found better fasting blood sugar and HbA1c in type 2 diabetes. Side effects are mostly gastrointestinal.

Quick pick

NOW Foods Brewer's Yeast Powder, 1 lb

from HerbsPro

Label: Dried, inactive, debittered brewer's yeast.

Best for trying one bottle: $11.86 one-time (checked Oct 15, 2026).

Shop at HerbsPro (paid link, opens in new tab)

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How we chose: Momentous is the partner brand we list first, so its product leads whenever the Where to buy list has one for this compound or a form in our Forms table. Otherwise, among partner brands that passed our vetting without conditions (others only when none sells it), the first product in that list whose name matches a form in our Forms table, else the first one listed. Not a claim that it works: check the amount per serving against the studied doses and limits.

Every graded outcome on this page

5 rows · line = participants
  1. Grade DFasting blood sugar and HbA1c in type 2 diabetesBlood sugarn 84
  2. Grade DBlood pressure and blood lipids in type 2 diabetesBlood pressuren 84
  3. Grade DPerceived milk supply and milk sugars in breastfeeding womenBreast milk supplyn 68
  4. No effectMilk production rate with lactation cookiesBreast milk supplyn 176
  5. No effectExpressed breast milk volume after preterm birthBreast milk supplyn 105
  6. 2 more graded outcomes, in the evidence chapter

Key facts

What it is
Dead (inactive) cells of the yeast Saccharomyces cerevisiae, used as a dietary supplement1
Milk output after preterm birth (105 mothers)
No clear effect at day 7: +94 mL/day vs placebo, 95% CI -51 to 239 mL/day2
Lactation cookies (176 parents)
No change in milk production rate vs ordinary cookies over 1 month4
Perceived supply (68 women)
65% vs 35% felt their milk supply rose on a yeast product; milk sugars (HMOs) did not change3
Type 2 diabetes (84 adults)
Fasting blood sugar and HbA1c improved vs placebo at 1,800 mg a day for 12 weeks5
Blood pressure (84 adults)
Systolic and diastolic pressure fell over 12 weeks at 1,800 mg a day in type 2 diabetes; blood lipids did not change7

What it is

Brewer's yeast is dried, inactive cells of the yeast Saccharomyces cerevisiae, sold as a powder or tablets and often used to try to raise breast milk supply.

How it works

Proposed

Brewer's yeast supplies B vitamins and chromium. The diabetes trial cites a proposed 'glucose tolerance factor' acting on insulin receptors, and LactMed attributes milk gains seen in ruminants to better nutrition rather than any specific effect on lactation.15

Forms, side by side

2 forms named in our sources. The rest show what our data holds, and say plainly where it holds nothing yet.

Brewer's Yeast (Inactive) forms compared

2 forms
Brewer's Yeast (Inactive) forms compared: 2 forms by 3 attributes. Empty cells are labelled No data yet, or Not graded in the evidence row.
2 formsDebittered brewer's yeast powder (dried, inactive)Brewer's yeast tablets or capsules
Absorption in peopleIn a 2026 isotope study (5 volunteers assessed), folate from brewer's yeast was 74% as bioavailable as a reference dose of 5-methyltetrahydrofolate; trials otherwise tracked milk volume, perceived supply and blood sugar.825Not measured.5
GI toleranceLactMed reports mostly gastrointestinal side effects in nursing mothers; in the BLOOM trial, side effects were similar to placebo.12No side-effect differences were reported in the BLOOM capsule trial.2
Studied forBreast milk supply (as a yeast product)Blood sugar in type 2 diabetes; milk supply after preterm birth
  1. Debittered brewer's yeast powder (dried, inactive)
    Absorption in people
    In a 2026 isotope study (5 volunteers assessed), folate from brewer's yeast was 74% as bioavailable as a reference dose of 5-methyltetrahydrofolate; trials otherwise tracked milk volume, perceived supply and blood sugar.825
    GI tolerance
    LactMed reports mostly gastrointestinal side effects in nursing mothers; in the BLOOM trial, side effects were similar to placebo.12
    Studied for
    Breast milk supply (as a yeast product)
  2. Brewer's yeast tablets or capsules
    Absorption in people
    Not measured.5
    GI tolerance
    No side-effect differences were reported in the BLOOM capsule trial.2
    Studied for
    Blood sugar in type 2 diabetes; milk supply after preterm birth
Every cell holds data from a cited page; citation numbers link to the page that holds them.Scroll the table for every column

What the human research says

Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.

Trial map

5 graded outcomes, largest study first

5 graded outcomes: 2 improved, 1 mixed, 2 no effect. The largest, a 2023 randomized trial of 176 people on milk production rate with lactation cookies, found no effect.

Bar: the ages a study enrolled (running to the edge when it states no upper or lower limit). Dot: only a mean age, counted as near your age within 5 years. Tick: the mean age inside a range.

1Milk production rate with lactation cookies: no effect, 18–45

3Blood pressure and blood lipids in type 2 diabetes: improved, mean age 46.3

4Fasting blood sugar and HbA1c in type 2 diabetes: improved, mean age 46.3

2Expressed breast milk volume after preterm birth: no effect, ages not stated

5Perceived milk supply and milk sugars in breastfeeding women: mixed, ages not stated

3. Blood pressure and blood lipids in type 2 diabetes: improved, 84 people34. Fasting blood sugar and HbA1c in type 2 diabetes: improved, 84 people4
5. Perceived milk supply and milk sugars in breastfeeding women: mixed, 68 people5
1. Milk production rate with lactation cookies: no effect, 176 people12. Expressed breast milk volume after preterm birth: no effect, 105 people2

1Milk production rate with lactation cookies

No effect · No-effect grade · RCT, 176 people, 2023

Exclusively lactating US parents of healthy 2-month-old infants

Dose, result and source
Every graded outcome on this page, largest study first
OutcomeFoundPeopleStudyWho was studied
Milk production rate with lactation cookiesNo effect176No-effect grade · RCT, 2023Exclusively lactating US parents of healthy 2-month-old infants
Expressed breast milk volume after preterm birthNo effect105No-effect grade · RCT, 2026Mothers in 3 Australian neonatal units who gave birth before 34 weeks (36 on brewer's yeast, 35 beta-glucan, 34 placebo)
Blood pressure and blood lipids in type 2 diabetesImproved84Grade D · RCT, 2013Adults with type 2 diabetes (Iran), alongside usual treatment; 90 randomised, 84 completed (same trial as the blood-sugar row)
Fasting blood sugar and HbA1c in type 2 diabetesImproved84Grade D · RCT, 2013Adults with type 2 diabetes (21 men, 63 women; mean age 46.3) in Iran, alongside usual treatment
Perceived milk supply and milk sugars in breastfeeding womenMixed68Grade D · RCT, 2025Breastfeeding women with a healthy infant aged 1 to 7 months (New Zealand)
Each circle is one graded outcome on this page, numbered from the largest study down, and placed by how many people it studied (log scale). By age shows the ages each study enrolled, where it states them. It shows who was studied and what was found, not advice about your dose.

Every graded row

5 rows

Showing 5 of 5 outcomes. Human trials only.

Grade DFasting blood sugar and HbA1c in type 2 diabetesBlood sugarBetter fasting sugar and HbA1cRCT
n 84 · 2013

Improved Changes in fasting blood sugar (P < 0.001), HbA1c (P < 0.001) and insulin sensitivity (P = 0.02) differed from placebo; BMI and insulin resistance did not change.

Design
RCT, n = 84, 2013
Population
Adults with type 2 diabetes (21 men, 63 women; mean age 46.3) in Iran, alongside usual treatment
Form
Brewer's yeast tablets
Dose
1,800 mg a day (six 300 mg tablets)
Duration
12 weeks
Source
Reference 5 · PubMed 24319552 (opens PubMed)
Grade DBlood pressure and blood lipids in type 2 diabetesBlood pressureLower BP; lipids unchangedRCT
n 84 · 2013

Improved Systolic and diastolic blood pressure fell in the brewer's yeast group (P = 0.007 and P = 0.001); LDL, HDL, triglycerides and total cholesterol did not change significantly.

Design
RCT, n = 84, 2013
Population
Adults with type 2 diabetes (Iran), alongside usual treatment; 90 randomised, 84 completed (same trial as the blood-sugar row)
Form
Brewer's yeast tablets
Dose
1,800 mg a day
Duration
12 weeks
Source
Reference 7 · PubMed 23967428 (opens PubMed)
Grade DPerceived milk supply and milk sugars in breastfeeding womenBreast milk supplyFelt more milk; milk sugars unchangedRCT
n 68 · 2025

Mixed Human milk oligosaccharides (the primary outcome) did not change; 65% vs 35% on placebo perceived more milk (p < 0.05), and formula use at 6 months was 4% vs 27% (p < 0.05).

Design
RCT, n = 68, 2025
Population
Breastfeeding women with a healthy infant aged 1 to 7 months (New Zealand)
Form
Saccharomyces cerevisiae yeast-based supplement (product not named in the abstract)
Dose
5 g a day
Duration
4 weeks
Source
Reference 3 · PubMed 40932299 (opens PubMed)
No effectMilk production rate with lactation cookiesBreast milk supplyNo better than plain cookiesRCT
n 176 · 2023

No effect Milk production rate rose 5.5 mL/h with lactation cookies and 5.8 mL/h with ordinary cookies (difference P = 0.948); perceived insufficient milk and self-efficacy also did not differ.

Design
RCT, n = 176, 2023
Population
Exclusively lactating US parents of healthy 2-month-old infants
Form
Cookies with oatmeal, brewer's yeast, flax seeds and fenugreek
Dose
56.5 g of cookies a day
Duration
1 month
Source
Reference 4 · PubMed 36921902 (opens PubMed)
No effectExpressed breast milk volume after preterm birthBreast milk supplyNo clear change in milk volumeRCT
n 105 · 2026

No effect Daily expressed milk on day 7 was 94 mL/day higher than placebo, but the 95% CI ran from -51 to 239 mL/day, so there was no clear effect; side effects were similar across groups.

Design
RCT, n = 105, 2026
Population
Mothers in 3 Australian neonatal units who gave birth before 34 weeks (36 on brewer's yeast, 35 beta-glucan, 34 placebo)
Form
Brewer's yeast capsules
Dose
Capsules daily (dose not stated in the abstract)
Duration
7 days
Source
Reference 2 · PubMed 42680572 (opens PubMed)

What the numbers add up to

Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.

Felt more milk, measured no more

In 68 women, more on a yeast product felt their supply rose (65% vs 35%), but in BLOOM and the cookie trial, measured milk output did not differ from placebo.324

How we got this: Comparison of self-reported and measured milk outcomes across the three lactation trials

Blood-sugar evidence is one trial

Only one 84-person, 12-week trial tested brewer's yeast for blood sugar, and its abstract reports P values but not the size of the change.5

How we got this: Evidence rows on this page

Studied doses

Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.

Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Doses studied in human trials

Doses studied in human trials ranged from 1,800 mg a day of brewer's yeast tablets for 12 weeks in type 2 diabetes to 5 g a day of a yeast-based product for 4 weeks in breastfeeding women; the BLOOM capsules were given for 7 days.532

When trials measured an effect

2 outcomes
How long trials ran before effects were measured
OutcomeMeasured atBasis
Fasting blood sugar, HbA1c and blood pressure in type 2 diabetes12 weeks (end of trial)1,800 mg a day vs placebo; measured only at baseline and week 1257
Perceived milk supplyWithin the 4-week trial5 g a day of a yeast-based product; measured milk sugars did not change3
When each outcome was assessed in the cited trials. It is not a promise of when anyone will notice a change.

Interactions and safety

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

What Brewer's Yeast meets

0 cited rows 2 tested together

Medicines 0

No medicine rows in our sources.

Brewer's Yeast0 medicines · 2 supplements

Supplements and foods 2

  • Tested together in a graded trial
Also cited: 2 tested together

  1. FenugreekFenugreek page

  2. FlaxseedFlaxseed page

Rows as our evidence profiles cite them; links stay on this site. Line weight shows what backs a row, not how serious an interaction is. No line means none was found in our sources, not that a combination is safe. Not medical advice: ask your pharmacist.

Interactions

0 agents

None found in our sources.

Check with what you take

Kept on this device only

Add what you take. We list every interaction our evidence profiles cite between Brewer's Yeast and your picks, and between your picks.

Most cited:

Add a supplement or medicine you take to check it against Brewer's Yeast.

Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.

Not medical advice, and no dosing advice. An empty result means no row we cite names that pair, by name or through a drug class we can link the medicine to, not that a combination is safe. Where our sources name only a group of medicines we cannot match, the cabinet says so. Ask your pharmacist before you combine supplements and medicines.

Who should be careful

5 groups
Breastfeeding
LactMed finds no scientifically valid human studies showing an effect on milk supply, and a multicentre trial found no meaningful difference in milk output from placebo. In an Australian survey of 592 mothers using it, 11% reported an adverse reaction, most often weight gain, stomach cramps, dry mouth and nausea; one of 108 South African mothers reported cramps in her infant.1
Product variability
LactMed notes wide variation in the content of brewer's yeast products.1
Diabetes medicines
In an 84-person trial, brewer's yeast taken alongside usual diabetes treatment lowered fasting blood sugar and HbA1c more than placebo, so anyone on glucose-lowering medicine should keep their clinician informed.5
Medicines and surgery
NCCIH advises that supplements may interact with medications or pose risks before surgery, and to tell your health care providers about everything you use.6
Pregnancy, breastfeeding and children
NCCIH notes that many dietary supplements have not been tested in pregnant women, nursing mothers or children.6
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.

How to read the label

What to check on the Supplement Facts panel.

How to read the label

2 checks
Dead yeast, not a live probiotic

LactMed describes brewer's yeast as dead Saccharomyces cerevisiae cells, so it is not the same as live probiotic yeast strains.1

Tablets vs powder

The diabetes trial used six 300 mg tablets a day (1,800 mg); powders list servings in grams, so compare by weight of yeast.5

Have the bottle? Photograph its Supplement Facts panel and see each line, brewer's yeast (inactive) included, beside the doses and forms the trials used in Label X-Ray.

Where to buy Brewer's Yeast (Inactive)

Products from brands we partner with that contain Brewer's Yeast (Inactive). Check the amount per serving against the doses studied above, and the label for other ingredients.

Brewer's Yeast (Inactive) products from partner brands

1 product
  • Quick pickHerbsProNOW Foods Brewer's Yeast Powder, 1 lb

    Dried, inactive, debittered brewer's yeast; label: 2 tablespoons (16 g) per serving with 7 g protein and 5 g fiber. The diabetes trial used 1,800 mg a day in tablets

    $11.86one-timeChecked Oct 15, 2026
    Shop at HerbsPro (paid link, opens in new tab)

Listing a product is not a claim that it works; check the amount per serving against the doses studied, and the label for other ingredients.Prices and labels are from each brand’s own site on the date shown; confirm before you buy.

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Frequently asked questions

Short answers to common questions; the numbers link to the sources below.

Common questions

7 answers
Does brewer's yeast increase breast milk supply?

Measured milk did not clearly change: in 105 mothers of preterm babies, the difference from placebo at day 7 was +94 mL/day with a 95% CI of -51 to 239. Lactation cookies with brewer's yeast did no better than plain cookies in 176 parents.24

Does brewer's yeast lower blood sugar?

One 84-person trial in type 2 diabetes found better fasting blood sugar and HbA1c vs placebo with 1,800 mg a day for 12 weeks, alongside usual treatment. No other trial on this page tested it.5

Does brewer's yeast interact with medicines?

No specific interaction is documented in LactMed or NCCIH guidance. Because one trial found lower fasting blood sugar and HbA1c alongside usual diabetes treatment, people on glucose-lowering medicine should keep their clinician informed.165

Is brewer's yeast safe while breastfeeding?

LactMed reports mostly gastrointestinal side effects in mothers and one report of infant cramps; in a survey of 592 Australian mothers using it, 11% reported a reaction such as weight gain or stomach cramps. In BLOOM, side effects matched placebo. LactMed also notes wide variation between products.12

Is brewer's yeast the same as probiotic yeast?

No. LactMed describes brewer's yeast supplements as dead (inactive) Saccharomyces cerevisiae cells, so they are not a live probiotic.1

Why do so many mothers say it works?

In 68 breastfeeding women, 65% on a yeast product vs 35% on placebo felt their supply rose, but milk sugars did not change, and trials that measured volume found no clear effect.32

How much brewer's yeast was studied?

1,800 mg a day of tablets in the diabetes trial and 5 g a day of a yeast-based product in breastfeeding women; the BLOOM abstract does not give its capsule dose.532

Sources

8 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.

Sources cited on this page

8 sources
  1. 1Brewer's Yeast. Drugs and Lactation Database (LactMed)Database National Institute of Child Health and Human Development, via NCBI Bookshelf, 2026 · ncbi.nlm.nih.gov
  2. 2Effect of brewers' yeast or beta-glucan derived from Saccharomyces cerevisiae on breast milk supply following preterm birth: the BLOOM randomised controlled trial.RCT Arch Dis Child Fetal Neonatal Ed, 2026 · PMID 42680572
  3. 3Saccharomyces cerevisiae Yeast-Based Supplement and Breast Milk Supply: A Randomised Placebo-Controlled Trial.RCT Matern Child Nutr, 2025 · PMID 40932299
  4. 4Effectiveness of lactation cookies on human milk production rates: a randomized controlled trial.RCT Am J Clin Nutr, 2023 · PMID 36921902
  5. 5Brewer's Yeast Improves Glycemic Indices in Type 2 Diabetes Mellitus.RCT Int J Prev Med, 2013 · PMID 24319552
  6. 6Using Dietary Supplements WiselyFact sheet National Center for Complementary and Integrative Health (NCCIH), 2019 · nccih.nih.gov
  7. 7Brewer's Yeast Improves Blood Pressure in Type 2 Diabetes Mellitus.RCT Iran J Public Health, 2013 · PMID 23967428
  8. 8Determination of Folate Bioavailability From Brewer's Yeast in a Dual Isotope Randomized Human Intervention Study.PK study Mol Nutr Food Res, 2026 · PMID 41954190

What changed

Every dated change to this page: what changed, who made it and why.

Change log

2 entries
Dated changes to this page
DateChangeWho and why
evidence, key facts, forms, who should avoid, FAQ, questions, time to effect, relatedAdded the blood-pressure report of the 84-person type 2 diabetes trial (lower blood pressure, lipids unchanged; grade D; between-group P values from full text), a 2026 isotope study on folate bioavailability (74% of a reference dose, in forms), a diabetes-medicine caution, time-to-effect rows, page questions, two FAQ answers (probiotic vs inactive yeast; interactions) and a goal-hub link. Breastfeeding note updated from LactMed (revised 2026-09-15: infant cramps report, BLOOM null). Interactions checked: LactMed lists none, LiverTox, NCCIH and MedlinePlus have no brewer's yeast entry, and PubMed holds only 1960s reports on yeast extract (a different product) with MAO inhibitors, so the interaction list stays empty. PubMed searched to 2026: BLOOM (2026) remains the newest milk-supply trial; no meta-analysis of brewer's yeast found.Writer: Kymata Health EditorialTrigger: A–Z audit against docs/supplements/AUDIT-STANDARD.md
allInitial editorial evidence review. Every PMID checked against NCBI E-utilities esummary (title, year, journal; none retracted) and each cited abstract read; numbers taken from the abstracts. Funding disclosed per study: Leiber GmbH donated BLOOM products and supported one author's institution; other abstracts name no funder (disclosed as not stated). Nulls shown: BLOOM 2026 and lactation cookies 2023; 2025 yeast-product trial shown as mixed (primary outcome null). Lactation rows sit under the healthy-aging goal. Safety from LactMed (NBK572248, revised 2026-09-15) plus NCCIH general guidance. Where to buy: NOW Foods Brewer's Yeast Powder (checked 2026-10-15).Writer: Kymata Health EditorialTrigger: new page

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