One study review found that eating an extra two to three servings of fruit or vegetables per day – which are high in potassium – was beneficial.
A lower salt intake would increase the benefits further, researchers said.
A stroke charity said a healthy diet was key to keeping stroke risk down.
While the increase of potassium in diets was found to have a positive effect on blood pressure, it was also discovered to have no adverse effects on kidney function or hormone levels, the research concluded.
As a result, the World Health Organization has issued its first guidelines on potassium intake, recommending that adults should consume more than 4g of potassium (or 90 to 100mmol) per day.
The BMJ study on the effects of potassium intake, produced by scientists from the UN World Food Program, Imperial College London and Warwick Medical School, among others, looked at 22 controlled trials and another 11 studies involving more than 128,000 healthy participants.
Where to find potassium
Potassium is an important mineral that controls the balance of fluids in the body and helps lower blood pressure.
It is found in most types of food, but particularly in fruit, such as bananas, vegetables, pulses, nuts and seeds, milk, fish, chicken and bread.
It is recommended that adults consume around 4g of potassium a day (or at least 90-100mmol).
That is equivalent to five portions of fruit and vegetables a day.
Our early ancestors would have had a diet very high in potassium – but food processing has markedly reduced the potassium content of food.
It is thought that the average potassium consumption in many countries is below 70-80mmol/day.
The results showed that increasing potassium in the diet to 3-4g a day reduced blood pressure in adults.
This increased level of potassium intake was also linked to a 24% lower risk of stroke in those adults.
Researchers said potassium could have benefits for children’s blood pressure too, but more data was needed.