Nutritional yeast (informally called nooch) is a deactivated (i.e., dead) yeast, often a strain of Saccharomyces cerevisiae, that is sold commercially as a food product. It is sold in the form of yellow flakes, granules, or powder, and may be found in the bulk aisle of natural food stores. It is used in vegan and vegetarian cooking as an ingredient in recipes or as a condiment.
It is a source of some B-complex vitamins and contains trace amounts of several other vitamins and minerals. It is often fortified with vitamin B12.