Supplement Forms/Alternate Names

  • Dried Yeast Fermentate; Faex; Faex Medicinalis; Levure De Biere; Medicinal Yeast; Saccharomyces cerevisiae ; Saccharomyces boulardii

Principal Proposed Uses

  • Protein Supplement; Treatment for Various Forms of Diarrhea , including Traveler’s Diarrhea, Antibiotic-associated Diarrhea, and Acute Diarrhea

Brewer’s yeast, also known as Saccharomyces cerevisiae , is commonly used in baking and the fermentation of beer; hence, the common name. Brewer’s yeast is rich in nutrients like chromium , B vitamins, protein, selenium , potassium , iron , zinc , and magnesium . It is the byproduct of beer brewing and can be grown on hops. Hops are the dried flowers that give beer its bitter taste. The yeast is separated from the beer after fermentation and processed. Aside from hops, the yeast can also be cultivated on other plants, like sugar beets.

Brewer’s yeast, along with its close cousin Saccharomyces boulardii , is considered a probiotic. Probiotics are foods or dietary supplements that contain organisms, like bacteria or yeast, which provide health benefits for humans. Along with brewer’s yeast, another example of a probiotic is yogurt with live and active bacteria cultures.

Bacteria and yeasts naturally live in our bodies, mainly in the digestive tract. Probiotics contain “good” bacteria or yeasts that keep our digestive tract functioning properly, as well as keeping the population of harmful or “bad” organisms low. 1 The probiotic activity of S. boulardii in particular has been studied in the treatment of a number of conditions including: 2,3,8

In addition to its probiotic benefits, Brewer’s yeast has been used as a protein supplement and is promoted as an energy and immunity enhancer.

This article covers both S. cerevisiae and S boulardii .


Brewer’s yeast is usually sold in the form of a powder, flakes, liquid, or tablets. It can also be found as part of other food products, like fermented milks. 7

Therapeutic Dosages

For adults, brewer’s yeast can be taken at a dose of 1-2 tablespoons per day. The powder form can be added to food or mixed with water or juice. 7

Probiotics, in general, should have several billion microorganisms per dose. This makes it more likely that the bacteria or yeasts will grow in the gut. 3

A standard dose of S. boulardii1 is 500 mg (milligrams) twice a day. This provides around 3 x 10 10-colony-forming units per gram. If taken to prevent antibiotic-associated diarrhea, for example, the yeast should be taken before and a few days after using antibiotics. The same is true for traveler’s diarrhea. 1

Therapeutic Uses

The strongest evidence supporting the benefits of brewer’s yeast is for diarrhea . Some studies have shown brewer’s yeast to be effective in preventing antibiotic-associated diarrhea, as well as relapsing colitis caused by the bacterium Clostridium difficile . S. boulardii may fight this form of diarrhea by making enzymes that counteract the effect of toxins produced by C. difficile . 2,3

Since brewer’s yeast is a rich source of the mineral chromium, it has been studied for its ability to improve blood sugar control in patients with diabetes. 6

There has also been interest in studying the effectiveness of brewer’s yeast for losing weight , lowering cholesterol , and preventing colds and flu . However, it is still uncertain whether it is effective in these situations. 2,4,7

What Is the Scientific Evidence for Brewer’s Yeast?

Determining the effectiveness of brewer’s yeast, as well as other probiotics, is hampered by the fact that many studies use combinations of differing bacterial and yeast strains. This makes it difficult to know whether only one or all of the components are needed for a beneficial effect. Nevertheless, a number of studies focusing only on S. boulardii or S. cerevisiae have shown beneficial effects.


Numerous studies have investigated the benefits of S. boulardii5,12,13 in antibiotic-associated diarrhea and traveler's diarrhea in adults.

A mathematical analysis of ten randomized, controlled studies found S. boulardii5 to be effective for the prevention of antibiotic-associated diarrhea.

In a controlled, double-blind study involving 3,000 Austrian tourists traveling through hot climates, researchers found that S. boulardii13 started five days before departure and continued through the duration of travel significantly reduced the incidence of traveler’s diarrhea compared to placebo. The effectiveness was dependent on the dose given and its preparation.

A systematic review of studies focusing on the effectiveness of S. boulardii in preventing C. difficile infection (the bacteria that causes antibiotic-associated diarrhea), found that the yeast may be effective in protecting against reoccurring infections, but not necessarily first-time infections. 11

Other studies have also shown that S. boulardii9,10 may reduce the duration of diarrhea in children.

Helicobacter Pylori

Helicobacter pylori , a common bacterium present in the stomach and upper intestines of some people, is associated with an increased risk of peptic ulcers. Treatment for H. pylori usually involves more than one antibiotic to suppress the bacteria. While there is little evidence that S. boulardii can help treat H. pylori , it may effectively reduce the side effects associated with standard treatment for this condition.

One clinical trial, for example, compared two groups of children aged 3-18 years infected with the H. pylori bacteria. One group was given medicines to treat the infection plus S. boulardii . The other group was given medicines plus a placebo. The group who took S. boulardii with their medicines had fewer side effects compared to the placebo group. 14 Side effects included bloating, taste problems, and nausea.

Cold and Flu

A large, randomized trial found a positive effect for brewer’s yeast in preventing colds and seasonal influenza (flu). In the study, 116 adults who had received a flu shot were given either 500 mg of a brewer’s yeast product called EpiCor or placebo for 12 weeks. Researchers found that those who received Epicor had fewer colds and flu. And those on Epicor who did get a cold or flu were sick for a shorter length of time compared to participants taking placebo. 4 Far more research is required before brewer’s yeast can be routinely recommended for the prevention of colds and flu.

Safety Issues

Brewer’s yeast, along with other probiotics, is generally considered safe. Some people may experience bloating or gas when taking probiotics. 1

Those who should practice caution when using probiotics include people who are severely sick, have immune system issues, or those who have central venous catheters. 3

People allergic to yeast or who are more likely to have yeast infections should not take brewer’s yeast. Also, people with diabetes should talk to their doctor before taking brewer’s yeast, since it can interact with their medicines and cause lower than expected blood sugar. 7

Always talk to a doctor before taking any supplement or medicine.

Interactions You Should Know About

People taking any of the medicines listed below should exercise caution when taking brewer’s yeast: 7

Antidepression Medications

Monoamine Oxidase Inhibitors (MAOIs)

Brewer's yeast has a substance called tyramine in it. Tyramine can interact with MAOIs and cause very high blood pressure which can be dangerous (hypertensive crisis). This can lead to a heart attack or stroke .

Pain Medication

Meperidine (Demerol)

Taking brewer’s yeast while taking Demerol may cause hypertensive crisis.

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