Bananas produce antimatter, but just barely. The main radioactive material in bananas is Potassium-40. A banana is about 0.358% potassium in all. About 0.012% of naturally occurring potassium is the radioactive Potassium-40. Only 0.001% of all radioactive decay events in postassium-40 produce an antiparticle (a positron).

An average banana produces a single positron about every 75 minutes.