Drinking a cup of beetroot juice every day may help reduce blood pressure, a new study suggests.

UK scientists looked at eight women and seven men with high blood pressure, but who were otherwise healthy.

Blood pressure is recorded as two numbers, such as 120/80. Systolic is the higher number and it refers to the pressure in the arteries when the heart beats. Diastolic is the smaller number and it refers to the pressure in the arteries between heart beats.

The study found that those who drank beetroot juice had reduced systolic and diastolic blood pressure compared to a group of controls who drank a placebo. This effect was most pronounced three to six hours after consumption of the juice, but was still present 24 hours later.

The scientists believe this is due to the presence of nitrate in the beetroot juice. In the body, nitrate is converted into a chemical known as nitrite and then into nitric oxide. Nitric oxide is a gas in the blood that is known to widen blood vessels, helping blood flow.

The participants drank either 250ml of beetroot juice or water and their blood pressure was then monitored for the next 24 hours. The juice contained about 0.2g of dietary nitrate, the same amount that would be found in a large bowl of lettuce.

"We were surprised by how little nitrate was needed to see such a large effect. This study shows that compared to individuals with healthy blood pressure, much less nitrate is needed to produce the kinds of decreases in blood pressure that might provide clinical benefits in people who need to lower their blood pressure," the scientists from London said.

However, they pointed out that it is unclear whether these effects are long-term.

"Our hope is that increasing one's intake of vegetables with a high dietary nitrate content, such as green leafy vegetables or beetroot, might be a lifestyle approach that one could easily employ to improve cardiovascular health," the scientists said.

Details of their findings are published in the journal, Hypertension.