Drinking 250ml (8oz) cut high blood pressure readings by 10mm of mercury (mmHg) in a study of 15 patients, bringing some into the normal range, the journal Hypertension reports.
Most marked after three to six hours, the effect was detectable a day later.
Scientists say the nitrate in beetroot widens blood vessels to aid flow. And many people with angina use a nitrate drug to ease their symptoms.
The researchers, from Barts and The London School of Medicine and Dentistry, who have been studying beetroot’s blood pressure lowering effects for years, say more work is still needed.
And they warn there could be one unexpected consequence of drinking beetroot juice – it can turn your urine pink.
Nitrate is found naturally in soil, where it is taken in by vegetables through the roots to help them grow.