Replete with a rich source of nutrients, brewer’s yeast continues to gain worldwide popularity for its functionality in human nutrition. Brewer’s yeast supplements are harvested from the unicellular budding fungi Saccharomyces cerevisiae. This yeast is considered nutritionally superior to all others.
Saccharomyces cerevisiae are more commonly recognized as the active yeasts responsible for the fermentation process of beers, wines, and other alcoholic drinks. The majority of yeast contained in dietary supplements is harvested from the by-products of beer making. In fact, brewer’s yeast obtains its bitter taste and unpleasant smell from this manufacturing process. However, brewer’s yeast may also be harvested upon other mediums such as sugar beets. By obtaining the yeast from this alternative source, brewer’s yeast supplements are said to retain a larger proportion of its key nutritional qualities, without adversely influencing smell or taste. Yeast not recovered from the brewing process are often labeled as “primary grown” brewer’s yeasts.
Brewer’s yeast has been used as a functional food for many centuries. Traditionally, the yeast’s most obvious use may well have been in the production of the intoxicating liquids we now refer to as wines. It was also used as both a flavor enhancer and therapeutic agent, treating a multitude of health conditions. Although knowledge regarding its nutritional content was lacking, cultures of the past continually praised its healing properties. Some scholars now believe that the ancient Egyptians (1550 â€“ 1500 B.C.) may have been among the first humans to harness its remedial powers.
The microscopic plant Saccharomyces cerevisiae is considered a significant source of B-complex vitamins, essential proteins, trace minerals, polysaccharides, and ribonucleic acid (RNA). It also contains the substances “skin respiratory factor, " SRF, and “glucose tolerance factor,” GTF.” Brewer’s yeast should not be confused with other dietary yeasts, which are not as nutritionally dense. These include; baker’s yeast, nutritional yeasts, and torula yeast.
Brewer’s yeast may be purchased in powdered, liquid, capsule, tablet, or flake form. Supplements are manufactured using the dry, crushed cells of the Saccharomyces cerevisiae fungi. The powdered forms of brewer’s yeast are often considered the most potent and manageable of all available forms. Australia’s “Vegemite” and England’s “Marmite” products are considered functional foods, which have been developed from brewer’s yeast.
Interestingly, many of the “primary grown” yeast supplements have been found to be lacking GTF, or “glucose tolerance factor.”
Live baker’s yeast should never be ingested, as live yeast cells have been shown to deplete the body’s supply of B-vitamins.
The nutrients found in brewer’s yeast have been extensively studied for their potential therapeutic applications. As a nutritional supplement, Saccharomyces cerevisiae is considered a rich source of many nutrients, including selenium. Epidemiological and clinical research has concluded that high-selenium containing brewer’s yeast may reduce the incidence of certain forms of cancer. [1, 2] Selenium and beta-glucans have exhibited anticarcinogenic and immunomodulatary effects when studied individually.  Because brewer’s yeast is a rich source of both nutrients, scientists speculate that these two agents may afford an explanation into this inhibitory effect.
Chromium-rich yeasts have also been a focal point in various clinical trials for the treatment of hyperglycemia, elevated cholesterol, and type II diabetes mellitus. When compared to chromium-lacking torula yeasts, chromium-rich yeast provided far greater results in these areas, improving both glucose tolerance and total lipid count in test subjects.  An increase in the sensitivity of insulin was also noted. This finding may prove especially relevant in the elderly population, as they are far more likely to be deficient in chromium. It has been proposed that chromium accomplishes this task via GTF, or “glucose tolerance factor.” Although this theory is relevant, the mechanism of action into the antidiabetic effect of high-chromium yeast remains unknown.
Other uses for brewer’s yeast include; wound/burn healing, hemorrhoidal preparations, and stress.  B-complex vitamins found in brewer’s yeast are the primary constituents thought to be responsible for the treatment of these three ailments.
Brewer’s yeast may also provide an extremely rich bio-available source for vegetarians, and persons lacking protein in their diet. 
Brewer’s yeast is not considered an essential nutrient and there have been no established dosages for its use. The normal recommended dose for a high potency yeast supplement ranges from 30 â€“ 60 grams per day, and is based upon individual tolerance. It may benefit individuals to gradually increase their intakes due to the possibility of GI distress. Most manufacturers suggest beginning at 15 â€“30 grams until well acclimated.
Brewers Yeast Toxicities and Precautions
There are no known toxicities associated with Saccharomyces cerevisiae and most supplements containing this fungus are considered safe. 
There have been adverse reactions reported in Europe. One case reported an individual who developed an invasive fungal infection after being administered Saccharomces boulardii, a well-known probiotic. Although the origin of infection did not start from brewer’s yeast, the later infection was identified as S. cerevisiae. 
Individuals with immune system impairments, yeast allergies, or females suffering from frequent yeast infections are not advised to supplement with brewer’s yeast until first consulting with a licensed healthcare practitioner.
Brewers Yeast Drug and Nutrient Interactions
Due to the significant amount of tyramine found in brewer’s yeast, persons taking the following prescription medications should be aware of the possible interactions.
- Monoamine Oxidase Inhibitors (MAOIs)
- Narcotic Pain Relievers
This natural substance is formed from the natural degradation of proteins and has been shown to induce “hypertensive crisis.” The intake of tyramine in persons taking these drugs may result in severe complications, including possible stroke and heart attack. 
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