ORCID

Abstract

This thesis evaluated nitrate metabolism and the link between cardiovascular health and periodontal disease. The first study compared effects of high-nitrate vegetables and pharmacological salt supplementation on the oral microbiome composition in hypertensive individuals. Seventy participants (50-70-y-old, clinical systolic BP (SBP) 130-159 mmHg, diastolic BP (DBP) <110 mmHg) were randomly allocated to group 1 (n = 24) consuming 300 mg/d nitrate in green leafy vegetables form, group 2 (n = 23) consuming 300 mg/d potassium nitrate in form of pills and low-nitrate vegetables, and group 3 (n = 23) consuming potassium chloride pills (placebo) and low-nitrate vegetables. Groups 1 and 2 showed similar microbial salivary changes, increased Neisseria species, and decreased Veillonella species post treatment, suggesting nitrate-dependent changes.The second study investigated oral health and microbiome composition of pregnant women with pre-eclampsia (n = 10, SBP = 150 ± 8 mmHg, DBP = 98 ± 9 mmHg) compared to normotensive pregnancies (n = 11, SBP = 111 ± 5 mmHg, DBP = 80 ± 9 mmHg). Pregnant women with pre-eclampsia showed higher plaque levels compared to normotensive pregnant women (P = 0.038), although activity of oral nitrate-reducing bacteria (P = 0.088) was not statistically significant. Plasma nitrate levels were significantly were lower in women with pre-eclampsia (P = 0.024). The third study evaluated the effect of chlorhexidine (CHX-M n= 21) and propolis (PROP-M n= 24) mouthwashes on abundance and activity of nitrate-reducing bacteria in healthy individuals. CHX-M increased relative abundance of nitrate-reducing bacteria (P < 0.001), but significantly impaired nitrate-reducing activity (P < 0.001) compared to baseline and PROP-M. PROP-M significantly increased plasma nitrate levels (P = 0.047) and reduced systolic BP (P = 0.022).The fourth study compared the effect of CHX-M, PROP-M, amoxicillin (AMX) and metronidazole (MTZ) on salivary nitrate-reducing activity within a 24-hour period using an in-vitro protocol. Results showed that MTZ significantly increased nitrate-reducing activity after 24-hours (P = 0.001) compared to all the other treatments (AMX, P = 0.025; CHX-M, P = 0.01; PROP-M, P = 0.023). Overall, this thesis suggests that poor oral health may impair the oral nitrate–nitrite pathway, thereby reducing nitrate bioavailability in women with pre-eclampsia. Diets rich in high-nitrate vegetables showed beneficial changes in the oral microbiome; however, these were not associated with blood pressure reduction. In contrast, use of propolis mouthwash increased plasma nitrate bioavailability, contributing to blood pressure reductions. Finally, it was observed metronidazole significantly enhanced nitrate-reducing activity.

Awarding Institution(s)

University of Plymouth

Supervisor

Raul Bescos Garcia, Zoe Brookes, Mary Hickson

Keywords

Nitrate, Nitrite, Nitric Oxide, Periodontal disease, Cardiovascular Health, Pre-eclampsia, Amoxicillin, Metronidazole, Dietary Nitrate, Nitrate-reducing Bacteria, Chlorhexidine, Propolis, Mouthwash, Antibiotics, Oral Health, Oral Microbiome

Document Type

Thesis

Publication Date

2025

Embargo Period

2026-01-06

Deposit Date

January 2026

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

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