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 the largest study of its kind.
Researchers at the University of Exeter conducted the study, published in the journal Free Radical Biology and Medicine, comparing responses between a group of older adults to that of younger adults. Previous research has shown that a high nitrate diet can reduce blood pressure, which can help reduce risk of heart disease.
Nitrate is crucial to the body and is consumed as a natural part of a vegetable-rich diet. 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.
The new 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.
Nitric oxide is key to healthy functioning of the blood vessels, and therefore the regulation of blood pressure.
Study author Professor Anni Vanhatalo highlighted that older people produce less nitric oxide as they age, and encouraging them to consume nitrate-rich vegetables could have significant long term health benefits. Alternatives to beetroot include spinach, rocket, fennel, celery, and kale.
The study recruited 39 adults aged under 30, and 36 adults in their 60s and 70s. Each group spent two weeks taking regular doses of nitrate-rich beetroot juice and two weeks on a placebo version. A bacterial gene sequencing method was used to analyze oral microbiome changes.
Both age groups experienced significant changes in their oral microbiome after drinking the nitrate-rich beetroot juice, though the changes differed.
In older adults, there was a decrease in the bacteria Prevotella and an increase in beneficial bacteria such as Neisseria. Their higher average blood pressure dropped after taking the beetroot juice, but not the placebo.
Professor Andy Jones noted that the study shows nitrate-rich foods can alter the oral microbiome in a way that may lower inflammation and blood pressure in older adults.
Dr. Lee Beniston from BBSRC praised the study for uncovering complex links between diet, microbiome, and healthy ageing, and for advancing knowledge with real-world benefits.
The paper is titled ‘Ageing modifies the oral microbiome, nitric oxide bioavailability and vascular responses to dietary nitrate supplementation.’
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The study is published in Free Radical Biology and Medicine.
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