A deactivated form of the yeast Saccharomyces cerevisiae, sold as flakes or powder, valued for a savory, umami, faintly cheesy flavor. It is related to brewer's yeast, a byproduct of beer fermentation, but nutritional yeast is grown deliberately, typically on molasses or sugar beet, and processed to be milder and less bitter. Popular in vegetarian and vegan cooking as a seasoning for popcorn, pasta, soups, and sauces, it naturally contains B-complex vitamins such as thiamine and riboflavin; many commercial brands are also fortified with vitamin B12, which yeast does not otherwise provide in meaningful amounts.