Nutritional yeast is a deactivated yeast, often a strain of Saccharomyces cerevisiae that is sold in the form of flakes or yellow powder. It has a strong flavor often described as nutty, cheesy, or creamy. It is used in cheese substitutes, as a flavor enhancer in mashed or fried potatoes, in scrambled tofu, and as a topping for popcorn.
Even in small amounts, nutritional yeast is a significant source of some B–complex vitamins. Some brands are fortified with additional B12. It has approximately 9 grams of protein in 2 tablespoons. It provides 9 amino acids that the human body cannot produce and 5% (unfortified) to 20% (fortified with B12) of recommended daily iron.
In large amounts, the high fiber content of nutritional yeast may cause digestive discomfort, and high niacin content can cause facial flushing. Some brands may contain tyramine, which can trigger migraines in some individuals.