Beetroot juice can reduce blood pressure in pregnancy, but why do some people not respond?

By looking at the bacteria present in women’s mouths, our researchers have been finding out why beetroot juice reduces blood pressure in some pregnant women with hypertension, while others do not respond to treatment.
  • Authors list

    Dr Elizabeth Cottrell, Dr Thomas Willmott, Dr Gavin Humphreys, Professor Andrew McBain, Professor Jenny Myers

    Start: 2018
    End: 2022

  • Research centre

  • Research status

    Completed projects

Why do we need this research?

Around 1 in 10 pregnant women and people have chronic hypertension – high blood pressure before or early in pregnancy. These individuals are more likely to experience pregnancy complications – such as pre-eclampsia, reduced growth, premature birth or stillbirth – because there isn’t enough blood flowing to the baby, meaning it can't get the food and oxygen it needs. There are very few treatments available to treat high blood pressure in pregnancy and we believe this needs to change.

Our scientists had already shown that drinking beetroot juice can reduce high blood pressure in pregnant women. This works because beetroot juice is a source of nitrate, which our bodies convert into nitric oxide – a small molecule that makes our blood vessels get wider and allows blood to flow more easily. However, the team found that some women were not able to make use of the nitrate in beetroot juice, meaning that they did not benefit from this treatment.

What happened in this project?

Bacteria living in our mouths and gut can affect how we metabolise – or process – certain foods. Previous research has shown that people may only benefit from dietary nitrate if they have certain bacteria in their mouths. Researchers funded by Tommy’s wanted to find out if this was also the case in pregnancy.

To do this, our researchers have been looking at the bacteria present in the mouths of women – both pregnant and non-pregnant – with either normal blood pressure or high blood pressure. By looking at samples from 55 women, they found that those with high blood pressure had lower levels of Veillonella – a type of bacteria that helps to process nitrate – on the surface of their tongue, meaning that they couldn’t metabolise nitrate as effectively as those with normal blood pressure. The team found no major differences between the pregnant and non-pregnant women, suggesting that pregnancy itself does not alter how nitrate is processed.

Our researchers also worked in the lab to see whether long-term supplementation with high doses of nitrate encouraged the growth of beneficial bacteria. The team found that the mixture of bacteria in samples was altered when nitrate was used in this way, with higher levels of the nitrate-processing bacteria detected after treatment.

What difference will this project make?

This study has helped us to understand why some people with high blood pressure benefit from drinking beetroot juice while others don’t. Next, the team want to carry out a larger clinical trial that will test whether long-term treatment with beetroot juice can change the mixture of bacteria in the mouths of pregnant women and people, and consequently reduce blood pressure.