Potassium is best known as the nutrient in bananas and leafy greens, but new research shows its importance goes far beyond muscle cramps.
A large clinical trial published in the New England Journal of Medicine found that patients at high risk of dangerous heart rhythms who raised their potassium levels into the high-normal range had fewer arrhythmias, fewer hospitalizations and better overall outcomes.
The study included 1,200 people in Denmark with existing heart conditions. Half followed their usual care, while the others received support to raise potassium through diet, supplements or medication when needed. After more than three years, the group with higher potassium levels had fewer serious rhythm problems and fewer unplanned hospital stays.
“A treatment-induced increase in plasma potassium level of approximately 0.3 mmol/L significantly reduced the arrhythmia burden without increasing the combined risk of hyper- or hypokalaemia,” said senior author Professor Henning Bundgaard.
Experts caution that the findings apply to people already at high risk and being closely monitored. Too much potassium can be harmful, especially for those with kidney disease.
But for most people, keeping potassium in the healthy range comes down to diet, eating fruits, vegetables, beans, nuts and dairy.
The trial was presented at ESC Congress 2025. It was funded by the Independent Research Fund Denmark, the Danish Heart Foundation and the Novo Nordisk Foundation.