Drinking beetroot juice twice daily for two weeks can significantly lower blood pressure in older adults, and researchers now think the secret lies in the mouth.
A new study from the University of Exeter reveals that the blood pressure-lowering effects of dietary nitrate may work by reshaping the oral microbiome, particularly by reducing specific bacteria linked to inflammation and impaired nitric oxide production.
Dietary nitrate, nitric oxide, and blood pressure
Nitrate is abundant in vegetables like beetroot, spinach, and arugula, and is known to support vascular health by increasing nitric oxide (NO) levels in the body. NO helps blood vessels dilate, improving blood flow and lowering blood pressure. However, this nitrate-to-NO conversion relies on oral bacteria, which may change with age.
In this double-blind, placebo-controlled study, 75 healthy adults were split into two groups: 39 under the age of 30, and 36 aged 67 to 79. Each participant consumed either nitrate-rich beetroot juice or a placebo version without nitrate for two weeks, with a two-week washout period in between. A third arm included antiseptic mouthwash, which is known to disrupt oral bacteria.
Older adults showed stronger blood pressure response
While both age groups showed changes in their oral microbiomes after consuming beetroot juice, only the older adults experienced a measurable drop in blood pressure. Their systolic pressure fell by an average of 7 mmHg, a reduction considered clinically meaningful.
- Older adults began with higher blood pressure (126/80 mmHg)
- Plasma nitrite levels rose significantly only in the older group
- Blood pressure changes were linked to specific shifts in oral bacteria
The most notable microbiome shift in older adults was a decrease in Prevotella and Veillonella species, bacteria that convert nitrate into ammonia rather than nitric oxide. These bacteria essentially “short-circuit” the beneficial pathway. In contrast, nitrate supplementation boosted levels of Neisseria, a genus that enhances nitric oxide production and is associated with vascular health.
Younger participants had different results
Despite similar changes in oral bacteria, younger adults did not experience a significant drop in blood pressure. Their baseline levels were already lower, averaging 117/72 mmHg. The study’s authors suggest that younger individuals may rely more on their own nitric oxide synthase pathways, which decline with age.
Mouthwash reduced vascular responsiveness
Interestingly, the antiseptic mouthwash condition reduced oral microbiome diversity in younger participants and led to decreased flow-mediated dilation, a measure of vascular responsiveness. This suggests that regular use of antiseptic mouthwash may interfere with nitric oxide production and cardiovascular 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 Professor Anni Vanhatalo. “Encouraging older adults to consume more nitrate-rich vegetables could have significant long term health benefits.”
Implications for diet, aging, and inflammation
Beyond blood pressure, the study suggests that dietary nitrate could play a broader role in managing age-related inflammatory conditions. The diminished presence of Prevotella and Veillonella in older participants following supplementation may have downstream effects on chronic inflammation, a contributor to diseases like arthritis and cognitive decline.
“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 Professor Andy Jones.
Journal: Free Radical Biology and Medicine
DOI: 10.1016/j.freeradbiomed.2025.07.002
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