A glass of concentrated beetroot juice each morning for two weeks changed which bacteria thrived inside older adults’ mouths, and those bacterial shifts came with a measurable drop in blood pressure. That is the central finding of a controlled human trial published in Free Radical Biology and Medicine in early 2025, which compared younger and older volunteers receiving the same nitrate-rich drink. Gene sequencing of participants’ saliva revealed that the juice selectively expanded species capable of converting dietary nitrate into nitrite, a precursor to nitric oxide, the signaling molecule that tells artery walls to relax.
The study also surfaced a less welcome finding: aging blunted the response. Older participants started with a different baseline oral microbiome and showed smaller vascular improvements from the same nitrate dose, suggesting that the mouth’s ability to act as a cardiovascular gatekeeper weakens over time. As of June 2026, the research has added fresh urgency to a question cardiologists and dentists rarely discuss together: could the bacteria living on your tongue influence whether your blood pressure medication is enough?
How the mouth became a blood-pressure organ
The biology behind this works through what researchers call the enterosalivary nitrate circuit. When you eat nitrate-rich food, whether that is beetroot, spinach, or arugula, the nitrate enters your bloodstream and is actively concentrated in your salivary glands. Saliva then bathes the tongue and palate, where specific bacteria, particularly species of Rothia and Neisseria, carry nitrate reductase enzymes that strip an oxygen atom from nitrate, turning it into nitrite. You swallow that nitrite, and in the acidic environment of the stomach and within blood vessel walls, it is converted into nitric oxide. Nitric oxide signals smooth muscle cells in arteries to relax, widening the vessels and lowering pressure.
Andrew Jones and Anni Vanhatalo, exercise physiologists at the University of Exeter who have studied dietary nitrate for over a decade, synthesized this multi-organ pathway in a review published in Medicine & Science in Sports & Exercise. Their work emphasizes that the circuit is not just a cardiovascular trick; it also supports oxygen delivery to working muscles, which partly explains why beetroot juice became popular among endurance athletes before it attracted attention from geriatricians.
Research published in Scientific Reports has reframed nitrate’s role even further, presenting evidence that it functions as a kind of prebiotic for the oral microbiome. Rather than acting like a drug that directly dilates blood vessels, nitrate appears to reshape the ecological balance of mouth bacteria, selectively feeding the taxa that carry the right enzymatic machinery. Network analysis of these communities has identified clusters of bacteria that rise and fall together in response to dietary nitrate and linked those clusters to cardiovascular and even cognitive markers.
The mouthwash experiments that proved the bacteria matter
If oral bacteria are truly the bottleneck, then killing them should erase the blood-pressure benefit. That is exactly what two independent clinical trials found.
In one, participants used chlorhexidine antiseptic mouthwash for a short period. Their salivary nitrate-to-nitrite conversion collapsed, plasma nitrite levels fell, and the blood-pressure reduction normally seen after dietary nitrate intake disappeared. A trial in men and women already being treated for hypertension reported that antibacterial mouthwash use was associated with higher systolic blood pressure, a striking result given that these participants were on medication specifically designed to keep their numbers down.
An earlier experiment reached the same conclusion through a slightly different design: chlorhexidine mouthwash reduced oral nitrate reduction, lowered circulating nitrite, and was linked to higher blood-pressure readings. Together, these studies form a consistent mechanistic chain. Dietary nitrate feeds specific oral species; those species produce nitrite; nitrite becomes nitric oxide; nitric oxide lowers pressure. Disrupt any link, and the benefit largely vanishes.
This does not mean you should throw away your mouthwash. Chlorhexidine is a prescription-strength antiseptic typically used for gum disease, not the same as an over-the-counter rinse. But the experiments do raise a practical question that most people have never considered: the products you use to clean your mouth might interact with the foods you eat to manage your blood pressure.
Why aging complicates the picture
The beetroot juice trial’s comparison of younger and older adults revealed that age reshapes the oral microbiome in ways that matter for this pathway. Older participants harbored a different starting community of bacteria and showed a smaller vascular response to the same nitrate dose. The reasons are not fully mapped, but several factors likely contribute: decades of antibiotic exposure, changes in saliva production, shifts in diet, and the cumulative effects of dental work and gum disease.
Gum disease, in particular, appears to be a significant modifier. A clinical trial published in npj Biofilms and Microbiomes found that periodontitis blunted the blood-pressure benefit of beetroot juice and that the benefit recovered after participants received periodontal treatment. That finding carries real-world weight: periodontitis affects roughly half of adults over 30 in the United States, according to CDC estimates, and prevalence climbs steeply with age. If inflamed gums suppress the very bacteria needed to process dietary nitrate, then oral health and cardiovascular health are linked in a way that neither dentists nor cardiologists routinely address.
The periodontitis study did not break down results by ethnicity or socioeconomic status, leaving open the possibility that access to dental care, not just gum disease itself, determines who benefits most from dietary nitrate. For older adults navigating both hypertension and limited dental coverage, this gap matters.
What the evidence cannot yet tell us
For all its mechanistic elegance, this line of research has real limitations that should temper enthusiasm.
The primary beetroot juice aging study does not report exact systolic blood-pressure reductions in millimeters of mercury for the older cohort, nor does it specify the nitrate dose in milligrams. Without those numbers, clinicians cannot translate the results into a precise dietary recommendation, such as how many milliliters of juice a 70-year-old with controlled hypertension should drink each day.
Participant-level data on concurrent blood-pressure medications are sparse. Many older adults take multiple drugs that affect vascular tone or kidney handling of sodium. Some of those medications could amplify or blunt the impact of nitrate-derived nitric oxide, but existing trials were not designed to tease apart those interactions.
Durability is another open question. The microbiome sampling in the primary trial covered a two-week window. Whether the bacterial shift persists after supplementation stops, or whether the blood-pressure benefit fades as the oral community reverts, has not been tested in longer follow-up. The mouthwash reversal studies suggest the microbial shift may be transient, which would mean nitrate-rich foods need to be consumed regularly, not sporadically, to maintain vascular benefits.
There is also a measurement problem. Most studies characterize the oral microbiome at the genus level, counting how many Rothia or Neisseria colonies appear before and after supplementation. But actual nitrate reductase enzyme activity can vary widely within a single genus or even between strains of the same species. Measuring baseline salivary enzyme activity, rather than just bacterial abundance, could be a better predictor of who responds to beetroot juice and who does not. No published trial has tested that hypothesis directly in adults over 65.
Safety reporting in older populations is thin as well. Beetroot juice can cause gastrointestinal discomfort in some people, and very high nitrate intakes have historically raised concerns about methemoglobinemia, though such events are extremely rare at the doses found in food or commercial juice concentrates. Existing studies have generally excluded participants with advanced kidney disease or severe heart failure, so the findings cannot be extended to those higher-risk groups without dedicated trials.
Where dietary nitrate fits in a blood-pressure plan
Several trials have reported that beetroot juice lowers blood pressure by a few millimeters of mercury. A randomized crossover trial in patients with hypertension, published before the microbiome work began, found meaningful reductions in blood pressure compared with a nitrate-depleted control drink. For an individual patient, a shift of two to five points on systolic pressure may not replace medication. At the population level, though, even small average reductions translate into fewer strokes and heart attacks over time.
The current evidence supports viewing nitrate-rich foods as a complementary strategy, not a stand-alone treatment, especially for older adults already on antihypertensive therapy. Beetroot juice is the most studied delivery vehicle, but leafy greens like spinach, arugula, and Swiss chard are also high in dietary nitrate. Cooking reduces nitrate content somewhat, so raw or lightly prepared vegetables retain more of the compound.
What makes this research line distinctive is that it reframes the mouth as an active participant in cardiovascular regulation, not just the place where digestion begins. The practical implications stretch beyond diet: dental hygiene, mouthwash choice, and periodontal treatment may all influence how effectively the body converts food into a blood-pressure-lowering signal. For older adults, whose oral microbiomes have shifted over decades and whose blood vessels are less responsive to nitric oxide, these details could matter more than they do for younger people.
Larger, longer trials in diverse older populations are needed before dietary nitrate can be formally incorporated into clinical guidelines. But the mechanistic evidence is now strong enough that the conversation between a patient and their doctor about blood pressure should probably include a question that would have seemed odd a decade ago: what is happening inside your mouth?
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*This article was researched with the help of AI, with human editors creating the final content.
