Dietary nitrate from beetroot lowered brachial and central blood pressure only in older adults, tracking with higher plasma nitrite and suppression of a Prevotella-dominated oral microbiome, according to a recent study.
In a double-blind, placebo-controlled, crossover study, researchers led by Anni Vanhatalo of the University of Exeter Medical School, UK, and colleagues, investigated whether aging modifies oral microbiome composition, nitric oxide bioavailability, and vascular responses to dietary nitrate. The trial enrolled 39 young adults (18–30 years) and 36 older adults (67–79 years). Participants completed three 14-day conditions with 14-day washouts: nitrate-rich beetroot juice (two 70-mL shots per day, each ≈595 mg nitrate), nitrate-depleted beetroot juice placebo (≈1 mg nitrate), and twice-daily antiseptic mouthwash. Outcomes included plasma and saliva nitrate and nitrite, brachial and central blood pressure (BP), flow-mediated dilatation (FMD), and pulse wave velocity. Tongue swabs underwent 16S rRNA sequencing (V1–V3), with non-metric multidimensional scaling and weighted co-occurrence network analysis; 486 operational taxonomic units were retained after filtering.
At baseline, older adults had higher mean arterial pressure vs the young (95 ± 9 vs 87 ± 7 mmHg). Nitrate supplementation increased plasma nitrate and nitrite about ten-fold in both groups, with larger nitrite rises in older adults. Only the older group exhibited BP reductions after nitrate: brachial mean arterial pressure decreased by 4 ± 4 mmHg, accompanied by decreases in central systolic, diastolic, and mean arterial pressures. The change in central mean arterial pressure correlated inversely with the change in plasma nitrite (r = −0.41). In young adults, BP did not change; however, FMD differed between mouthwash and nitrate conditions, and mouthwash reduced percentage FMD by 12%. Pulse wave velocity was unchanged in both age groups. Placebo modestly increased plasma nitrate and was associated with small favorable BP changes in older adults, smaller than with nitrate.
The oral microbiome shifted after nitrate in both cohorts and differed by age post-supplementation, whereas placebo and mouthwash did not alter overall composition; mouthwash reduced alpha diversity in the young (Shannon index). With nitrate, Neisseria species (for example, N. bacilliformis, N. flavescens, N. elongata) increased, particularly in older adults. In older participants, higher plasma nitrite correlated with decreases in a module dominated by potentially pathobiotic, ammonia-producing taxa, including Prevotella dentalis (r = −0.88), Prevotella intermedia (r = −0.72), and Crassaminicella sp. SY095 (r = −0.81).
The researchers reported no conflicts of interest.
