Yeast extract is the term used to describe yeast products that are made through a process that removes the cell wall of the yeast culture. The contents of the cell -- the yeast extract -- is then used as nutritional supplements or food additives.
As a supplement, it can be consumed as a liquid, in capsules, or in food spreads. The supplement has a high concentration of nutrients including protein, a series of B vitamins, folic acid, and chromium. Vegetarians often use yeast extract as a substitute for meat, dairy and other sources of protein.
As a food additive, it has a savory taste much like bouillon, and so has been used to help bring out the tastes and flavors of certain foods. It is contained in most processed savory foods on the market today, including savory snacks, ready-made meals, and popular sauces. Producing yeast extract concentrates the yeast flavor, so it need only be used in small quantities to have the desired effect.