Bananas Are Slightly Radioactive

That familiar yellow fruit (Review) is famous for being a great source of potassium, an essential mineral for our bodies. However, a tiny fraction of all naturally occurring potassium is an isotope called potassium-40. Unlike its stable cousin, potassium-40 is unstable and weakly radioactive, meaning it occasionally decays and releases a minuscule amount of radiation. This isn't unique to bananas; this same isotope is found in many other potassium-rich foods, including potatoes, kidney beans, and sunflower seeds. It's a natural and unavoidable part of our environment and the food we eat.

To help put this low level of radiation into perspective, scientists and science communicators developed the "banana equivalent dose" or BED. It's an informal unit used to explain exposure to other, more significant sources of radiation in relatable terms. For instance, a single dental x-ray is equivalent to eating about 500 bananas, while a cross-country flight exposes you to the radiation of about 400. This clever comparison highlights just how trivial the radioactivity of a single banana truly is.

There's no need to give up your favorite smoothie ingredient. Our bodies are excellent at maintaining a stable level of potassium through a process called homeostasis. When you eat a banana, any excess potassium, including the radioactive potassium-40, is simply filtered out and excreted. To receive a lethal dose, you would have to consume an impossible 10 million bananas in one sitting, a scenario where the radiation would be the least of your worries.