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Randomized Controlled Trial
. 2024 Sep;154(9):2696-2706.
doi: 10.1016/j.tjnut.2024.07.002. Epub 2024 Jul 16.

The Effect of Dietary Nitrate on the Oral Microbiome and Salivary Biomarkers in Individuals with High Blood Pressure

Lisa du Toit  1 , Michaela L Sundqvist  2 , Alvaro Redondo-Rio  3 , Zöe Brookes  4 , Patricia Casas-Agustench  1 , Mary Hickson  1 , Alicia Benavente  3 , Gemma Montagut  3 , Eddie Weitzberg  5 , Toni Gabaldón  6 , Jon O Lundberg  5 , Raul Bescos  7
Affiliations
Randomized Controlled Trial

The Effect of Dietary Nitrate on the Oral Microbiome and Salivary Biomarkers in Individuals with High Blood Pressure

Lisa du Toit et al. J Nutr. 2024 Sep.

Abstract

Background: Green leafy vegetables (GLV) contain inorganic nitrate, an anion with potential prebiotic effects on the oral microbiome. However, it remains unclear whether GLV and pharmacological supplementation [potassium nitrate (PN)] with a nitrate salt induce similar effects on the oral microbiome.

Objectives: This study aimed to compare the effect of GLV with PN supplementation on the oral microbiome composition and salivary biomarkers in individuals with high blood pressure.

Methods: Seventy individuals were randomly allocated to 3 different groups to follow a 5-wk dietary intervention. Group 1 consumed 300 mg/d of nitrate in form of GLV. Group 2 consumed pills with 300 mg/d of PN and low-nitrate vegetables. Group 3 consumed pills with potassium chloride (placebo: PLAC) and low-nitrate vegetables. The oral microbiome composition and salivary biomarkers of oral health were analyzed before and after the dietary intervention.

Results: The GLV and PN groups showed similar microbial changes, probably nitrate-dependent, including an increase in the abundance of Neisseria, Capnocytophaga, Campylobacter species, and a decrease in Veillonella, Megasphaera, Actinomyces, and Eubacterium species after the treatment. Increased abundance of Rothia species, and reduced abundance of Streptococcus, Prevotella, Actinomyces, and Mogibacterium species were observed in the GLV group, which could be nitrate-independent. GLV and PN treatments increased salivary pH, but only GLV treatment showed an increase in the salivary buffering capacity and a reduction of lactate.

Conclusion: The combination of nitrate-dependent and nitrate-independent microbial changes in the GLV group has a stronger effect to potentially improve oral health biomarkers compared with PN.

Keywords: leafy green vegetables; microbiome; nitrate; nitric oxide; nitrite; oral health.

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Figures

FIGURE 1
FIGURE 1
Changes (delta) in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and heart rate (HR) before (pre) and after (post) the dietary intervention. GLV, green leafy vegetables group; PLAC, placebo group; PN, potassium nitrate group. Values are mean ± SD.
FIGURE 2
FIGURE 2
β-Diversity in the potassium nitrate (PN), placebo (PLAC), and green leafy vegetables (GLV) groups before (dotted lines) and after (continuous line) the dietary intervention.
FIGURE 3
FIGURE 3
Heatmap of differentially abundant genera (A) and species (B) after the dietary intervention in the 3 groups (PLAC, placebo group; PN, potassium nitrate group; GLV, green leafy vegetables group). Only taxa that significantly changed in any of the groups are reported. The effect size corresponds to the effect of the treatment estimated with linear models.
FIGURE 4
FIGURE 4
Differential abundance of nitrate-reducing species after the dietary intervention in the 3 groups (PLAC, placebo group; PN, potassium nitrate group; GLV, green leafy vegetables group). The P value corresponds to the raw P value obtained with linear models.
FIGURE 5
FIGURE 5
Correlations at baseline between bacterial genera and salivary parameters. Heatmap of effect size and significance of the correlation as estimated with Spearman’s correlation analysis (A). Correlations of Veillonella (B) and Campylobacter (C) abundance and salivary parameters.
See this image and copyright information in PMC

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