A banana equivalent dose (abbreviated BED) is an informal expression of ionizing radiation exposure, intended as a general educational example to indicate the potential dose due to naturally occurring radioactive isotopes by eating one average sized banana. One BED is often taken as 0.1 µSv, however, in practice this dose is not cumulative as the principal radioactive component is excreted to maintain metabolic equilibrium. The BED is only an indicative concept meant to show the existence of very low levels of natural radioactivity within a natural food, and is not a formally adopted dose quantity.