I hear you… Yes! Bananas are radioactive. Not just bananas, but also most of the objects you encounter in your everyday life are radioactive too. Indeed, even you are radioactive! Let’s focus on bananas for now.
Bananas are rich in potassium. The radioactivity in bananas is due to the presence of potassium, which usually contains a trace amount of an isotope of potassium – potassium-40 (K-40). This has a half-life of 1.25 billion years. The beta decay of the potassium-40 emits beta particles, along with the gamma rays from the gamma decay of the isotope. This is the reason why bananas are radioactive. Commercial radioactive detectors often detect radiations, from a large heap of bananas, usually when transported in a large mass.
Does this mean bananas are not safe?
NO IT DOESN’T! BANANAS ARE SAFE! Bananas are good for health, just like any other fruits. Our body usually stabilizes the contents, that we intake and keep them at a constant level. It does the same with potassium and the isotope potassium-40. The biological half-life of potassium-40 is about 30 days and it is eliminated from the body regularly by homeostasis.
You need not worry about the potassium-40, as you do intake it daily by drinking water and inhaling. Potatoes are rich in potassium too. It would take 1 sievert (100 rems) of radiation to start affecting the human body. Eating a banana just exposes you to 78× 10-9 seiverts. It would take about thirteen million bananas to expose you to a radiation level of 1 sievert.