Bacteria in the mouth determine whether taking beetroot could lower hypertension risk in pregnancy

In a new study, our researchers at the Tommy’s Maternal and Fetal Health Research Centre in Manchester investigated whether the quantity of certain oral bacteria is different between women with high and normal blood pressure.

They then looked at how differences in these bacteria could make beetroot more or less effective at reducing high blood pressure.

We know that one of the ways that blood pressure is controlled is through the activity of the compound nitric oxide. 

Nitrate, commonly found in green leafy vegetables and beetroot, can be used in our bodies to make nitric oxide. The first step in this process involves nitrate being converted into nitrite by bacteria in our mouths. Nitric oxide can then be formed, which acts on our blood vessels causing them to relax and widen, helping to reduce blood pressure.  

Our team's earlier work found that a daily shot of nitrate-rich beetroot juice was only effective at reducing blood pressure in some, but not all, hypertensive pregnant women.  

In their new study, published in the journal Hypertension on Wednesday 13 September, our researchers looked at the amount of bacteria in different people’s mouths to see whether it impacts how well beetroot works at reducing blood pressure.  

The study included pregnant women with high and normal blood pressure, as well as non-pregnant women with high and normal blood pressure.

Following an overnight fast, plasma, saliva and tongue scraping samples were collected and measured for nitrate and nitrite and for profiling of the microbiota – the organisms present in the mouth. Blood pressure was measured and then participants were given a 70ml shot of beetroot juice containing nitrate. Measurements were taken again 2-3 hours later.

The results

The results show that being pregnant does not significantly impact the activity of nitrate converting bacteria in the mouth, or the amount of nitrite (produced by the bacteria) that is in saliva.

However, the study did show that women (both pregnant and not pregnant) with high blood pressure have less of the bacteria in their mouths that can break down nitrate, particularly a group of bacteria called Veillonella, and lower nitrite in their saliva.  

Participants with more of the nitrate-converting bacteria had better resting blood pressure and showed a stronger response to beetroot juice.

Dr Thomas Willmott, who carried out the study as part of his PhD at the Tommy’s Centre at the University of Manchester, said:

“We can see through this research how important the oral microbiome is in determining resting blood pressure and how different individuals respond to dietary nitrate. Essentially, the more nitrate being converted into nitrite by the bacteria in the mouth, the more effective beetroot is at lowering blood pressure.”  

What's next?

Dr Elizabeth Cottrell, senior author of the study, said:

“If we can find a way to increase the amount of these beneficial bacteria in the mouth, it could be a way to help manage high blood pressure.  

“There is potential for dietary interventions, such as beetroot supplementation, to help increase the amount of these bacteria in our mouths, which could then help lower blood pressure and reduce the risk of serious pregnancy complications such as preeclampsia.”

This study was small, with 55 people (28 pregnant, 27 not pregnant) taking part, and shows the need for larger clinical studies to look at whether dietary supplementation may be useful for preventing and treating hypertension during pregnancy.

Why is this research needed?

Hypertensive pregnancy disorders – preeclampsia, gestational hypertension and chronic hypertension – affect around 10% of pregnancies and cases are on the rise.

These blood pressure disorders increase the risk of maternal and neonatal death. They can also have long-term health impacts for mothers and babies, including women and birthing people being at increased risk of heart disease and stroke later in life.

Screening for preeclampsia has been advanced through the recent development of a rapid blood test which can identify women at risk, but it’s also vital that work to reduce that risk in the first place continues, including new approaches to manage blood pressure. 

Tommy’s researchers have been exploring interventions which could help prevent hypertensive disorders in pregnancy.