The blood pressure-lowering effect of nitrate-rich beetroot juice in older people may be due to specific changes in their oral microbiome, according to research from the University of Exeter, UK, that compared responses to the juice in older and younger adults.

Previous research had shown that a high-nitrate diet can reduce blood pressure, which can help reduce risk of heart disease. When the older adults drank a concentrated beetroot juice “shot” twice a day for two weeks, their blood pressure decreased – an effect not seen in the younger group. Nitric oxide is key to healthy functioning of the blood vessels, and therefore the regulation of blood pressure.

The study provides evidence that this outcome was likely caused by the suppression of potentially harmful bacteria in the mouth. An imbalance between beneficial and harmful oral bacteria can decrease the conversion of nitrate (abundant in vegetable-rich diets) to nitric oxide.

“We know that a nitrate-rich diet has health benefits, and older people produce less of their own nitric oxide as they age," said study author Anni Vanhatalo, PhD. "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.”

The study recruited 39 adults under age 30 and 36 adults in their 60s and 70s. Each group spent two weeks taking regular doses of beetroot juice and two weeks on a placebo version of the juice with nitrate stripped out. Each condition had a two week “wash out” period in between to reset. The team then used a bacterial gene sequencing method to analyze which bacteria were present in the mouth before and after each condition.

In both groups, the make-up of the oral microbiome changed significantly after drinking the beetroot juice, but these changes differed between the younger and older age groups. The older age group experienced a notable decrease in the mouth bacteria Prevotella after drinking the 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 beetroot juice, but not after taking the placebo supplement.

To read the study, published in Free Radical Biology and Medicine, click here