Almost everything around us is radioactive to some degree, though most of the time it is not significant enough to even make a difference when it comes to our overall health.
A lot of people wonder why or how bananas are radioactive, being the healthy fruit it is. Bananas are radioactive because of the isotope of potassium in them. Potassium-40 contains around .01 percent of total potassium and has a half-life of about 1.24 billion years.
The radiation contained in bananas is not nearly significant enough to do any harm whatsoever to the human body, even when this fruit is consumed in large amounts.