Brewer’s yeast is derived from the unicellular fungus Saccharomyces cerevisiae, which causes the fermentation process basic to the brewing of beer. Dried brewer’s yeast is a rich source of several nutrients, including the B vitamins thiamin, riboflavin, niacin, pyridoxine, pantothenic acid, folate, vitamin B12 and biotin, and such trace minerals as chromium and selenium. It also contains beta-glucans, ribonucleic acid or RNA. Para-aminobenzoic acid and myo-inositol. A substance isolated from brewer’s yeast called skin respiratory factor or SRF has found application in some cosmetic and wound-healing products, as well as in some hemorrhoidal preparations.

Brewer’s yeast has been a popular nutritional supplement for many years. Much of the brewer’s yeast marketed for nutritional supplement use is grown specifically for that marketplace. The supplements are prepared from dry, crushed cells of Saccharomyces cerevisiae. The cells are not alive.