What do bananas and beetroot have that other foods don't?

"We need to reduce our salt intake and eat more foods which are high in potassium. It has been proven that this helps to reduce blood pressure, protects us from the damage caused by hypertension and prevents cardiovascular illnesses developing," says Dr Judit Soto.

To give us an idea of how skewed the balance between salt and potassium is, she warns that "in general, a normal diet nowadays makes us eat six times more salt than we should and four times less than the minimum recommended amount of potassium".

Potassium is good for us because it helps to eliminate sodium through the urine, thereby reducing blood pressure.

The top ten foods especially high in potassium are bananas, potatoes and sweet potatoes, pistachio nuts, tomatoes, avocado, soya, chickpeas, cocoa, mushrooms and watercress.

We already know what bananas have that other foods don't, but what about beetroot? In its case, the 'virtue' is that it provides nitric acid, which relaxes and dilates the blood vessels, helping to improve circulation and reduce blood pressure. A study by the British Heart Foundation showed that drinking a glass of beetroot juice every day for two weeks reduced the upper figure by an average of 7.7mmGh and the lower figure by 5.2.

Other foods which are interesting because of their concentration of nitrates are green leafy vegetables, such as rocket, kale, and spinach.