"We saw no evidence that a diet lower in sodium had any long-term beneficial effects on blood pressure. Our findings add to growing evidence that current recommendations for sodium intake may be misguided," said Lynn Moore from Boston University school of medicine, and the lead researcher.

Instead, eating plenty of potassium, calcium and magnesium every day did more to keep blood pressure in check, the researchers found when they looked at the diets and salt intake of 2,632 men and women aged between 30 and 64. Those who ate the highest amounts of potassium and sodium also recorded the lowest blood pressure levels.

Of these, Dr Moore thinks that potassium—derived from foods such as avocado, spinach, sweet potato, bananas and coconut water—has the most important role to play in maintaining healthy blood pressure levels. Spinach, chard, almonds and black beans are rich in magnesium, while calcium is found in milk and cheese, soya beans and nuts.