Nutritional yeast is a deactivated yeast, typically from the strain Saccharomyces cerevisiae, that is grown specifically for use as a food product. It is often used in vegan and vegetarian cooking as a cheese substitute because of its rich, savory, and slightly nutty flavor, often described as “umami.” It comes in the form of yellow flakes, granules, or powder and is commonly sprinkled on foods or added to sauces.