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Nitric Oxide. 2019 Aug 1;89:54-63. doi: 10.1016/j.niox.2019.04.010. Epub 2019 Apr 30.

Dietary nitrate supplementation alters the oral microbiome but does not improve the vascular responses to an acute nitrate dose.

Author information

1
Institute of Clinical Health and Exercise Sciences, University of the West of Scotland, Blantyre, G72 0LH, Scotland, UK.
2
Institute of Health Research & Innovation, Division of Biomedical Science, University of the Highlands and Islands, Inverness, IV2 3JH, Scotland, UK.
3
Department of Life Sciences, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, G4 0BA, Scotland, UK.
4
Institute of Clinical Health and Exercise Sciences, University of the West of Scotland, Blantyre, G72 0LH, Scotland, UK. Electronic address: chris.easton@uws.ac.uk.

Abstract

Nitrate (NO3-) contained in food and beverages can transiently increase nitric oxide (NO) availability following a stepwise reduction to nitrite (NO2-) by commensal bacteria in the oral cavity. We tested the hypothesis that regular ingestion of dietary NO3- would influence the oral microbiome, the capacity to reduce NO3- to NO2- in saliva, and the vascular responses to an acute dose of NO3-. The abundance of bacterial species on the tongue, the availability of NO markers, and vascular function were assessed in 11 healthy males before and after 7 days of supplementation with NO3--rich beetroot juice and a NO3--depleted placebo. As expected, saliva and plasma NO2- and NO3- were significantly elevated after NO3- supplementation (all P < 0.05) but not placebo. We found that NO3- supplementation increased salivary pH (7.13 ± 0.54 to 7.39 ± 0.68, P = 0.043) and altered the abundance of some bacteria previously implicated in NO3- reduction: Neisseria (from 2% ± 3%-9% ± 5%, P < 0.001), Prevotella (from 34% ± 17%-23% ± 11%, P = 0.001) and Actinomyces (from 1% ± 1%-0.5% ± 0.4%). Despite these alterations to the oral microbiota, an acute dose of NO3- increased salivary and plasma NO2-, reduced systolic blood pressure and increased the response to flow mediated dilation to a similar extent before and after 7 days of supplementation (P > 0.05). Our study establishes that supplementing the diet with NO3- for a sustained period can alter the oral environment in favour of health but does not impact the response to an acute NO3- dose. Acute ingestion of NO3- results in transient improvements in vascular function but the dietary induced adaptations to the oral bacteria did not enhance these effects.

PMID:
31051259
DOI:
10.1016/j.niox.2019.04.010

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