British researchers found that just around a pint of the juice led to dramatic reductions in blood pressure within hours.

The effect was traced to nitrate in the beetroot that reacted with bacteria in the mouth.

This led to chemical changes that resulted in blood vessels dilating to increase blood flow.

Study leader Professor Amrita Ahluwalia, from the William Harvey Research Institute at St Bartholomew’s Hospital in London, said: “Drinking beetroot juice, or consuming other nitrate-rich vegetables, might be a simple way to maintain a healthy cardiovascular system.”

Other vegetables with high levels of nitrates include green leafy varieties such as spinach and lettuce.

High blood pressure is linked to half of all heart disease and 75 per cent of strokes.