Beet juice has been praised for its blood-pressure-lowering benefits, but new research suggests those benefits may also depend on your age – and your mouth. Scientists have discovered that the bacteria on your tongue play a critical role in whether dietary nitrate from beets is successfully converted into nitric oxide, a molecule that improves circulation, heart function and exercise performance. But the benefits were very different between older and younger adults, revealing a previously unknown link between aging, the oral microbiome and vascular health.
Scientists at the University of Exeter set out to investigate how nitrate interacts with the oral microbiome, and whether age plays a factor in how beneficial this nutrient is. From a broader group of 75 participants, some younger (18-30 years) and some older (67-79 years), which the researchers used to find initial trends, an age-based subgroup of 26 (13 aged 18-22 and 13 aged 70-79) underwent detailed crossover testing to examine how nitrate-rich beet juice affected blood pressure and oral bacteria across age groups. Beets have been touted as one of nature’s superfoods, rich in a range of vitamins and nutrients, and shown promise in benefiting people with high blood pressure.
But what does this have to do with our mouths? Unlike many other nutrients, nitrate – found in vegetables like beets, spinach, arugula/rocket and lettuce – doesn’t get processed and absorbed in the gut. Instead, after you eat nitrate-rich foods, the nutrient enters the bloodstream and around a quarter of it stays concentrated in saliva glands to be cycled through the oral microbiome. Here, oral bacteria found only on the tongue convert nitrate to nitrite. Nitrite is then swallowed and converted to nitric oxide when passing through low-oxygen regions along the gastrointestinal tract.
This final form of nitrate is a gas that helps regulate blood flow, blood pressure, immune response and brain function. It relaxes and widens blood vessels, which improves circulation and reduces cardiovascular strain. Nitric oxide also helps our muscles use oxygen more efficiently during exercise. While the body can produce it naturally, this ability declines with age, stress, and disease, making dietary sources like beets incredibly important in later life.
But the important first step on this biochemical pathway takes place in the oral microbiome.
In the study, the 26 healthy participants underwent three separate 10-day interventions, drinking a nitrate-rich beet juice, a nitrate-depleted placebo beet juice, and beet juice while also using antiseptic mouthwash (control). Blood samples, tongue swabs, and vascular health measures were taken before and after each juice period.
What they found was that the older cohort, following the beet juice intervention, had a significant reduction in 24-hour systolic and diastolic blood pressure (BP), and their tongue’s bacterial composition had been altered – nitrate-reducing bacteria like Veillonella increased, while Actinomyces and Neisseria decreased. While Actinomyces doesn’t normally play a role in nitrate metabolism, Neisseria does. (The researchers suggest this might reflect complex age-related shifts or compensatory changes in the microbiome.)
In the younger group, the researchers found that nitrate had no significant impact on BP, and changes to tongue bacteria after the beet juice intervention didn’t promote nitrate-metabolizing bacteria. While both age groups experienced a rise in plasma nitrate/nitrite, as well as exhaled nitric oxide – showing absorption worked across both cohorts – the downstream health impacts were vastly different.
In the control group – where mouthwash killed off bacteria in the oral microbiome, BP remained the same as baseline for the older participants (as well as the younger volunteers). Nitric oxide levels were also reduced, suggesting that subduing that tongue bacteria limited the amount of dietary nitrate available to be processed and absorbed.
The placebo group had no changes to BP or oral bacteria composition, as somewhat expected.
“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,” said co-author Andy Jones, a professor at the University of Exeter. “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.”
While the study was small and short, and health measurements were rather superficial – surface-level oral swabs, BP being the only vascular marker taken into account – it nonetheless offers new insight into the often under-appreciated role the bacteria in our mouths play in promoting important biological functions downstream.
It also sheds new light on how the oral microbiome changes with age. For example, it makes sense that more nitrate-receptive bacteria would populate the mouth as we age, when we’re more likely to need nutritional assistance from our diet to maintain cardiovascular health and function.
“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, a professor at the University of Exeter. “They also tend to have higher blood pressure, which can be linked to cardiovascular complications like heart attack and stroke. Encouraging older adults to consume more nitrate-rich vegetables could have significant long term health benefits.”
The study also reveals the need for more research focusing on this area of age-related medicine and opens the door for age-specific interventions that harness the untapped power of the oral microbiome – which, much like the gut, is still not well understood. The microbial module that responded most strongly to dietary nitrate in older adults (called MM6O) included several species linked to chronic inflammation and immune dysfunction. So regulating this group could potentially have an impact on conditions like age-related cognitive decline and infection response.
“This research is a great example of how bioscience can help us better understand the complex links between diet, the microbiome and healthy aging,” said Lee Beniston from the UK’s Biotechnology and Biological Sciences Research Council . “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 research was published in the journal Free Radical Biology and Medicine.
Source: University of Exeter