Nutritional yeast is a deactivated yeast that is often used as a food supplement. It is rich in vitamins, particularly B vitamins, and is a good source of protein, making it popular among vegetarians and vegans. The flakes or powder have a cheesy, nutty flavor, which makes it a popular seasoning for various dishes. This ingredient is often fortified with vitamin B12, an essential nutrient that is typically found in animal products. Nutritional yeast can be sprinkled on popcorn, added to sauces, or used in recipes to enhance flavor while providing additional nutrients.