As its name implies, brewer’s yeast was originally identified as a primary ingredient in the beer-making process.1 As with other plants, the yeast family has many members, all of which are one-celled fungi. Brewer’s yeast, or Saccharomyces cerevisiae, is specifically grown as a nutritional substance rich in chromium, selenium, proteins and B-complex vitamins.1

Single-celled yeast organisms were first used in baking and fermentation 4,000 years ago in ancient Egypt.2 Centuries later, famed French microbiologist Louis Pasteur discovered that alcohol was the natural by-product of yeast fermentation.2

Background

As a probiotic, brewer’s yeast lives naturally in the digestive tract, creating the balance of yeasts, bacteria, and enzymes to form a critically stable environment. As one of more than 1,500 species of yeasts in existence, brewer’s yeast is one of the better-known and most valued member of this eukaryotic kingdom.2

Science

Depending on the intended use, brewer’s yeast has differing mechanisms of action. As a dietary supplement, brewer’s yeast is a nonliving, dried product.3 Overall, the mechanisms of action of brewer’s yeast are largely dictated by its nutrients.

The substantial chromium content of brewer’s yeast is responsible for significant improvement in potentiating human insulin receptors, decreasing insulin resistance and increasing beta-cell function in the pancreas.3

Brewer’s yeast supplements also are commonly used to enhance immunity. One small trial enrolled more than 100 patients during the cold-and-flu season. Participants were given either 500 mg of a standardized brewer’s yeast supplement or placebo every day for 12 weeks and were monitored periodically for cold and flu symptoms. Three months later, patients who had taken the active brewer’s yeast supplement experienced 16% fewer symptoms, and the symptoms that did develop were 11% shorter in duration.4

Perhaps the most exciting potential for brewer’s yeast is in cancer treatment. Bench researchers are exploring the in vitro use of brewer’s yeast cells incorporated into breast-cancer-cell cultures. Actively metastatic breast-cancer cells are known to be aggressively phagocytic, engulfing and destroying surrounding healthy cells. When brewer’s yeast cultures were introduced into the cell cultures and subsequently phagocytized, apoptosis of the cancer cells rapidly escalated.

After only 30 minutes, 13% of the cells died, with the rate increasing to 38% at four hours.5 As might be expected, breast-cancer cells that were actively metastatic were more vulnerable to the brewer’s yeast cells, showing a 629% increase in apoptosis when compared with normal cells and a 178% increase for the more stable, nonmetastatic breast-cancer cells.5

Another intriguing use is in the treatment of premenstrual syndrome. Participants in one clinical trial were randomized to placebo or a brewer’s yeast-based supplement. Using the Menstrual Distress Questionnaire (MDQ), participants were monitored for a period of six months at both the follicular and luteal phases of their cycles. Although the placebo users showed significant improvement in their MDQ scores, the treatment group far exceeded those, with an 82% reduction in symptoms by the end of the trial.6

Multiple studies have been conducted using various forms of probiotics to treat and prevent antibiotic-associated diarrhea. Most of these cases are attributable to Clostridium difficile. Use of brewer’s yeast supplements in conjunction with traditional antibiotic treatments has been shown to reduce the duration of symptoms as well as the rate of infection recurrence.7

Safety, drug interactions

Brewer’s yeast contains the amino acid tyramine. If taken in conjunction with a monoamine oxidase inhibitor or the pain medication meperidine (Demerol), the resulting interaction can cause a hypertensive crisis.8

Allergies are always a potential with any botanical product, so people with a known sensitivity to yeast should avoid these supplements.

Persons with diabetes should be careful when taking brewer’s yeast. If taken in significant quantity, the supplement can reduce serum glucose levels.8 Drugs that are metabolized through the cytochrome P-450 enzyme chain, such as antifungals, may reduce any anticipated action of the yeast supplement.3

Although studies have indicated that persons with Crohn’s disease should avoid brewer’s yeast supplements due to a potential for exacerbation of the illness, a review of several clinical trials showed conflicting results.3

Cost, how supplied, dose

Brewer’s yeast is available in many forms, including tablets, flakes, powder, and liquid. The dose used in most studies is 500 mg daily of yeast equivalent. Brewer’s yeast has not been studied in pregnant or lactating women or in young children and should not be used in those populations. Brewer’s yeast supplements are relatively inexpensive, with a month’s supply costing no more than $10.1

Summary

Health-care providers need to be able to direct patients to products that are safe as well as effective. Brewer’s yeast is one supplement that is affordable, effective and readily available.

References

1. University of Maryland Medical Center. Brewer’s yeast.

2. Legras JL, Merdinoglu D, Cornuet JM, Karst F. Bread, beer and wine: Saccharomyces cerevisiae diversity reflects human history. Mol Ecol. 2007;16:2091-2102.

3. Natural Medicines Comprehensive Database. Brewer’s yeast. 

4. Moyad MA, Robinson LE, Zawada ET Jr, et al. Effects of a modified yeast supplement on cold/flu symptoms. Urol Nurs. 2008;28:50-55.

5. Ghoneum M, Gollapudi S. Induction of apoptosis in breast cancer cells by Saccharomyces cerevisiae, the baker’s yeast, in vitro. Anticancer Res. 2004;24:1455-1463.

6. Facchinetti F, Nappi RE, Sances MG, et al. Effects of a yeast-based dietary supplementation on premenstrual syndrome. A double-blind placebo-controlled study. Gynecol Obstet Invest. 1997;43:120-124.

7. Kovacs DJ, Berk T. Recurrent Clostridium difficile-associated diarrhea and colitis treated with Saccharomyces cerevisiae (Baker’s yeast) in combination with antibiotic therapy: a case report. J Am Board Fam Pract. 2000;13:138-140.

8. Tufts Medical Center. Brewer’s yeast.

All electronic documents accessed July 15, 2011.