Nitrate-rich beetroot juice lowered blood pressure in older adults by altering oral microbiome composition. Digest
The body's ability to generate nitric oxide, a molecule involved in keeping blood pressure under control, falls with age, but providing oral microbes with nitrate-rich foods may help to compensate for this decline by generating more of its precursor, nitrite. Researchers set out to test how age affects responses to nitrate-rich beetroot juice and to antiseptic mouthwash, and whether shifts in oral bacteria explain changes in cardiovascular function.
The trial enrolled 39 younger adults (18–30 years) and 36 older adults (67–79 years). Each person completed three two-week treatment periods. The first two periods followed a randomized double-blind crossover design: all participants received both nitrate-rich and nitrate-depleted beetroot juice in different orders, without knowing the treatment. The third period tested antiseptic mouthwash in an open-label format, meaning participants knew which treatment they were given.
The findings suggest that age shaped both vascular responses and the oral microbiome:
In both age groups, nitrate-rich juice raised nitrate and nitrite in blood and saliva by about tenfold, while there were no meaningful changes with placebo or mouthwash.
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Older adults began with higher blood pressure than younger ones. After nitrate-rich juice, systolic pressure decreased by 7 mmHg and diastolic by 2 mmHg, while no changes were observed in the younger group.
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Nitrate caused a shift in the overall bacterial community in both age groups, but the resulting composition differed by age. Placebo and mouthwash had no effect.
Species that support nitrite formation increased, while bacteria that divert nitrite away from nitric oxide production declined. These shifts were stronger in older adults.
Only in young adults, antiseptic mouthwash reduced bacterial diversity and weakened arterial dilation.
The findings suggest that nitrate from beetroot juice improved blood pressure in older adults because their oral microbiome shifted toward species that favor nitric oxide production. In younger adults, the microbiome also shifted and plasma nitrite levels rose, but blood pressure remained unchanged. This may reflect that their nitric oxide system was already functioning effectively and, combined with their lower starting blood pressure, left little room for additional benefit from the higher nitrite levels. By contrast, only in the young did mouthwash reduce microbial diversity and impair arterial dilation. This difference suggests that vascular function in younger adults may depend more on overall microbial diversity, whereas in older adults the key factor was specific compositional changes that influenced nitrite handling.
Because the trial had an exploratory approach, relied on genetic markers of bacteria rather than full genomic profiling and assessed nitric oxide only indirectly through nitrate and nitrite levels, further studies are needed to confirm these results. Learn more about lifestyle strategies to lower blood pressure and reduce disease risk in Aliquot #105.