Listerine May Clean Your Mouth, But It Could Weaken Blood Vessel Function In Young Adults

From Beetroot To Mouthwash: How Oral Bacteria Influence Blood Pressure and Vascular Function

EXETER, England — Daily use of Listerine may disrupt the important balance of oral bacteria that help regulate cardiovascular function, according to new research that reveals an unexpected connection between oral health and blood vessel performance.

Scientists at the University of Exeter discovered that oral bacteria perform a metabolic conversion process, transforming dietary nitrates from leafy greens into nitric oxide (a compound needed for healthy blood vessels). When researchers studied 75 people across different age groups, they found that two weeks of Listerine use reduced bacterial diversity and altered blood vessel function in younger adults, while nitrate-rich beetroot juice boosted beneficial bacteria and improved blood pressure in older adults.

The research uncovered a surprising age divide: older adults who drank beetroot juice experienced meaningful blood pressure drops, while healthy younger participants saw no cardiovascular benefits from the same treatment. This points to fundamental changes in how aging bodies process these protective compounds.

How Mouth Bacteria Affect Heart Health

The bacteria living on our tongues aren’t just sitting there passively. They actively process the food we eat and convert nitrates into forms our bodies can use. When this system works properly, it creates a backup pathway for producing nitric oxide that becomes increasingly important with age.

The research involved 75 participants across two groups: 39 healthy adults under 30 and 36 adults in their 60s and 70s. Each group underwent three separate two-week treatment periods with washout periods in between to reset their systems.

Participants were given either nitrate-rich beetroot juice containing 750 milligrams of nitrate daily, a placebo version with nitrates removed, or using Listerine twice daily. Scientists collected tongue swabs, blood samples, and measured blood pressure before and after each treatment to track changes in both oral bacteria and cardiovascular health.

Older adults who consumed beetroot juice showed increases in beneficial bacteria like Neisseria species, which contain genes for producing nitric oxide. At the same time, they experienced decreases in potentially harmful bacteria including Prevotella species, which are linked to inflammation and various health problems including high blood pressure.

Nitric oxide helps blood vessels relax and maintain healthy blood pressure, but aging bodies become less efficient at producing this vital molecule through normal biological pathways.

Why Age Matters for Beetroot Juice Benefits

The research revealed dramatic differences between age groups that began before any treatments were initiated. Older participants had higher baseline blood pressure (averaging 126/80 mmHg compared to the younger group’s 117/72 mmHg). After two weeks of consuming beetroot juice, only the older adults experienced meaningful reductions in brachial blood pressure, with an average decrease of 4 mmHg in mean arterial pressure.

Previous research has shown that chlorhexidine-containing mouthwash can elevate blood pressure within just seven days of use. The current study tested Original Listerine, which contains different active ingredients. Although it did not raise blood pressure, it did reduce blood vessel reactivity in younger adults after two weeks of twice-daily use.

These beneficial effects in older adults weren’t just incidental. Changes in oral bacterial communities were correlated with higher nitric oxide levels in blood and subsequent reductions in blood pressure. Older adults who showed the greatest increases in beneficial bacteria also had the largest improvements in blood pressure.

Listerine vs. Heart Health: What the Research Shows

Listerine disrupted the oral ecosystem in notable ways. While it didn’t dramatically alter the overall composition of oral bacteria, regular use reduced bacterial diversity and impaired blood vessel function in younger adults. This indicates that overly aggressive oral hygiene practices could inadvertently affect bacteria that support cardiovascular health.

The research doesn’t mean people should abandon oral care, but rather points toward a more thoughtful approach. Maintaining oral health remains important, but completely sterilizing the mouth with antiseptic mouthwash may reduce helpful bacteria along with harmful ones.

For older adults concerned about rising blood pressure, this research offers scientifically backed reasons to increase consumption of nitrate-rich vegetables. Foods like arugula, spinach, kale, and beetroot contain the raw materials needed to support the nitrate-nitrite-nitric oxide pathway that becomes increasingly important with age.

Rather than focusing solely on medications, clinicians could potentially recommend specific dietary interventions that work with the body’s natural bacterial ecosystem to support heart health. The study claims to be the largest investigation of its kind examining how oral bacteria mediate the cardiovascular effects of dietary nitrates.

Despite two very different findings, the study does show one clear indication: aging fundamentally alters how our bodies respond to certain dietary interventions. Understanding these changes could unlock new approaches to preventing age-related cardiovascular disease, without abandoning beneficial oral hygiene practices.

Disclaimer: This report summarizes findings from a peer-reviewed scientific study. It is intended for informational purposes only and should not be taken as medical advice. Always consult a healthcare professional before making changes to your diet, oral care, or medication.