Are Bananas Really Radioactive?

Every time we read a list of fun facts about the world, there is one piece of information that is always there. Supposedly, bananas are radioactive. But is that statement true? Are these delicious yellow fruits actually filled with radioactive elements? You’re about to find out.

Getty Images / Moment / Javier Zayas Photography

It is true that bananas are radioactive. But so are spinach, potatoes, white beans, oranges, brazil nuts, and even the human body. Basically, bananas have three kinds of potassium isotopes: K-39, K-40, and K-41. The second kind, K-40, spontaneously decays, releasing electrons and gamma rays. However, this radioactive isotope makes up only 0.012% of the potassium element; and the K-40 atom is barely radioactive: it has a half-life of 1.3 billion years. This means that only a few thousand atoms decay each second.

So if you were wondering how many bananas you would have to eat to become radioactive, we recommend you save your precious time. That is because a typical adult body contains about 140g of potassium as a natural component – which is about 16mg potassium-40. To put this in perspective, the human body is 280 times more “radioactive” than a banana. Eating one banana temporarily increases your total amount of potassium-40 by 0.4%, but that amount is quickly balanced out by your metabolism.