The approximate radiation dose one gets from eating a banana is 0.1 microsieverts. A microsievert (μSv) is one millionth of a sievert, which is the unit used to measure the health effect of low levels of ionizing radiation on the human body.
A lethal dose of radiation is approximately 5 sieverts, which is equal to 5,000,000 (5 million) microsieverts.
So, if we want to get a lethal radiation dose from bananas, we would need to eat: