Researchers suggest beetroot may lower blood pressure by reducing “bad” oral bacteria

Older people who experience the blood pressure-lowering effect of nitrate-rich beetroot juice may be benefiting from changes in their oral microbiome, suggests the recently published and largest study on the subject.

Scientists at the University of Exeter, UK, compared responses between a group of older adults to that of younger adults. When they drank a concentrated beetroot juice shot twice a day for two weeks, their blood pressure decreased — an effect not observed among the younger participants.

The study builds on previous research supporting a high-nitrate diet for reducing blood pressure, which can help lower the risk of heart disease. Nitrate is crucial to the body and is commonly found in certain vegetables, which are converted into nitric oxide. Nitric oxide is key to the healthy functioning of the blood vessels by helping regulate blood pressure.

“We know that a nitrate-rich diet has health benefits, and older people produce less of their own nitric oxide as they age. They also tend to have higher blood pressure, which can be linked to cardiovascular complications like heart attack and stroke,” says study author, professor Anni Vanhatalo, from the University of Exeter, UK.

“Encouraging older adults to consume more nitrate-rich vegetables could have significant long-term health benefits. The good news is that if you don’t like beetroot, there are many nitrate-rich alternatives like spinach, rocket, fennel, celery, and kale.”

Suppressing harmful mouth bacteria

The paper, published in Free Radical Biology and Medicine, links beetroots’ blood pressure benefits to the suppression of potentially harmful bacteria in the mouth. It highlights that an imbalance between beneficial and harmful oral bacteria can decrease the conversion of nitrate to nitric oxide. 

The study recruited 39 adults aged under 30, and 36 adults in their 60s and 70s through the National Institute for Health and Care Research Exeter Clinical Research Facility. Each group spent two weeks taking regular doses of nitrate-rich beetroot juice and two weeks on a placebo version of the juice without nitrate.

Each intervention group had a two-week “wash-out” period in between to reset.

The team then used a bacterial gene sequencing method to analyze bacteria present in the mouth before and after each intervention.

In both groups, the oral microbiome composition changed significantly after drinking the nitrate-rich beetroot juice, but these changes differed between the younger and older age groups.

Specific strains’ benefits

The older age group experienced a notable decrease in the mouth bacteria Prevotella after drinking the nitrate-rich juice, and an increase in the growth of bacteria known to benefit health, such as Neisseria.

The older group also had higher average blood pressure at the start of the study, which fell after taking the nitrate-rich beetroot juice, but not after taking the placebo supplement.

“This study shows that nitrate-rich foods alter the oral microbiome in a way that could result in less inflammation, as well as a lowering of blood pressure in older people. This paves the way for larger studies to explore the influence of lifestyle factors and biological sex in how people respond to dietary nitrate supplementation,” says co-author, professor Andy Jones, at the University of Exeter.

Dr. Lee Beniston, associate director for Industry Partnerships and Collaborative Research and Development at Biotechnology and Biological Sciences Research Council, which funded the research, says: “This research is a great example of how bioscience can help us better understand the complex links between diet, the microbiome, and healthy aging.”

“By uncovering how dietary nitrate affects oral bacteria and blood pressure in older adults, the study opens up new opportunities for improving vascular health through nutrition.”

The paper, titled “Aging modifies the oral microbiome, nitric oxide bioavailability, and vascular responses to dietary nitrate supplementation,” is published in the journal Free Radical Biology and Medicine.

In other scientific inquiries into beetroot, a recent women’s health study found that 12 weeks of supplementing with nitrate-rich beetroot extract significantly improves carotid artery stiffness in postmenopausal females, a group at higher risk of cardiovascular disease.