Radioactive bananas

Radioactive bananas. That doesn't sound good, doesn't it? What does this mean? Should we be afraid of glow-in-the-dark bananas?

Well, some foods do contain small amounts of radioactive elements. Food can gain this radioactivity in a couple of ways [1] Uptake: roots of plants take in radionuclides from the soil, [2] Deposition: radioactive particles in the air settle onto crops, or [3] Bioaccumulation: radionuclides accumulate in animals that ingest plants, feed, or water containing radioactive material.

Potassium-40 - the scientific notation is ⁴⁰K) - is a radioactive isotope of potassium which has a long half-life of 1.251×10⁹ years. It makes up 0.012% (120 ppm) of the total amount of potassium found in nature.

The most well known example of naturally-occurring radionuclides in foods are bananas. Bananas have naturally high-levels of potassium and, as I mentioned above, a small fraction of all potassium is radioactive. Each banana can emit .01 millirem (or 0.1 microsieverts) of radiation.

Is that worrysome, you may ask. No, because this is a very small amount of radiation. To put that in context, you would need to eat about 100 bananas to receive the same amount of radiation exposure as you get each day from natural radiation in the environment.

Besides, your body maintains its potassium balance by excreting potassium that has been ingested. Eating potassium rich food results in excretion of potassium, maintaining the body’s appropriate potassium equilibrium.