https://www.bbc.co.uk/news/magazine-34225517

But for a healthy person, “it would be impossible to overdose on bananas,” says Collins. "You would probably need around 400 bananas a day to build up the kind of potassium levels that would cause your heart to stop beating… Bananas are not dangerous - and in fact they are, and always have been, very good for you."

Adults should consume about 3,500mg of potassium per day, according to the UK’s National Health Service. The average banana, weighing 125g, contains 450mg of potassium, meaning a healthy person can consume at least seven-and-half bananas before reaching the recommended level.

There are some people who should steer clear of foods that are high in potassium though, warns Collins - those with kidney disease.

“These patients have a very low kidney function which can potentially see a build-up of harmful potassium levels in their blood stream because they can’t get rid of the mineral when they pass urine,” she says. “So in theory it is possible for someone with kidney disease to die of a high blood potassium level if they decided to consume lots of different food types rich in the mineral.”

She once had a patient on dialysis who had a heart attack after eating too many tomatoes - another fruit rich in potassium. His kidneys had already stopped working so he was unable to get rid of the excess.

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