Bananas are radioactive...so how many exactly would you have eat to die? Is it possible to calculate?
Wikipedia's article on the Sievert, a unit used to measure radiation, tells us a banana's output measures about 0.098 μSv.  The lowest fatal dose listed is 4.5 Sv.  So we know the radiation from forty-six million bananas would be enough to kill.

Annual world production of bananas is around 18 million tonnes, and at 125g per banana, that's enough to kill 3000 people every year if all the bananas are produced on the same day instead of throughout the year and if the bananas are arranged in spheres around the people to maximize radiation exposure. The same mass could probably be used to crush or suffocate a larger number of people.