Try to eat less than a million bananas a year

Why? Bananas are naturally slightly radioactive. While it’s unlikely your body could retain all that radioactive potassium in those bananas, if it did you’d absorb enough radiation to cause an increased cancer risk:

xkcd radiation chart

There are disputes about those figures, of course, but at ~105 calories a banana, you’re getting roughly 143 times your daily allotment of 2000 calories, so probably you should cut back anyway.

-the Centaur

P.S. One BED (Banana Equivalent Dose) is 0.1 microsieverts of radiation. XKCD claims that 100 millisieverts of radiation is the lowest dose linked to increased cancer risk. Take that with a grain of salt … but do the math.