Dietary Nitrate Intake in Vegetarians and Omnivores

Not Applicable

Completed

• Conditions: Blood Pressure
• Interventions: Other: Placebo mouthwash; Other: Chlorhexidine mouthwash

• Registration Number: NCT03871777
• Lead Sponsor: University of Plymouth

Brief Summary

Vegetarian diets are commonly associated with lower blood pressure levels. This has been related to greater consumption of inorganic nitrate, since vegetables are the main source of this anion. Dietary nitrate is reduced to nitrite by commensal bacteria in the mouth, which in turn leads to increased circulatory nitrite availability. Nitrite can form nitric oxide by several pathways promoting a reduction in the vascular tone and lower blood pressure.

Detailed Description

Not available

Study Timeline

• Study Start: 2016-05-09
• Primary Completion: 2017-09-04
• Study Completion: 2018-11-12
• Study First Submitted: 2019-03-09
• Study First Submitted QC: 2019-03-09
• Study First Posted: 2019-03-12
• Status Verified: 2019-10
• Last Update Submitted: 2019-10-09
• Last Update Posted: 2019-10-10

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 41

Inclusion Criteria

• Healthy vegetarians (vegans and ovo-lacto vegetarians) following this dietary pattern for at least a year.
• Health omnivores

Exclusion Criteria

• Smokers
• Individuals taking any medications or recreational drugs.
• Individuals with pre-existing medical conditions such as hypertension, diabetes, dyslipidaemia or dental conditions (gingivitis).
• Individuals using mouthwash or tongue scrapes were excluded from this study

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Omnivores	Chlorhexidine mouthwash	Healthy omnivores with similar characteristics of vegetarians (age, body mass index, gender and physical activity levels) formed this arm
Vegetarians	Placebo mouthwash	Healthy vegetarians (vegans and lacto-ovo vegetarians) 18 and 50 years formed this arm.
Vegetarians	Chlorhexidine mouthwash	Healthy vegetarians (vegans and lacto-ovo vegetarians) 18 and 50 years formed this arm.
Omnivores	Placebo mouthwash	Healthy omnivores with similar characteristics of vegetarians (age, body mass index, gender and physical activity levels) formed this arm

Primary Outcome Measures

Name	Time	Method
Dietary nitrate intake	7 days	Macro- and micronutrient intake of seven-day food diaries were analysed using a nutritional analysis software programme (Microdiet, Downlee Systems, Chapel-en-le-Frith, UK). Nitrate content of vegetables was mainly obtained from the European Food Safety Authority and additional data for spinach and lettuce from the Food Standards Agency. Nitrate and total polyphenol figures were uploaded to the Microdiet database prior to analysis.
Change oral microbiome	7 days	bundance of oral bacteria was analysed using 16S ribosomal ribonucleic acid (rRNA) after using the placebo mouthwash and antibacterial mouthwash.; Salivary DNA was extracted using a DNA kit (QIAamp® DNeasy Blood \& Tissue Kit). Polymerase chain reaction (PCR) amplification of the 16S rRNA V1-2 region was carried out using universal 16S primers 27 F (5'-AGA GTT TGA TCM TGG CTC AG-3') and 338 R (5'-GCW GCC WCC CGT AGG WGT-3'). Single band PCR products were purified and quantified with Qubit 2.0 Fluorometer (Invitrogen, CA, USA). Sequencing was performed on an Ion Torrent Personal Genome Machine.
Change in Resting Energy Expenditure	7 days	Resting Energy Expenditure was analysed using indirect calorimetry after using the placebo mouthwash and antibacterial mouthwash
Concentration of nitrate and nitrite in plasma and saliva	7 days	Whole blood was collected into lithium-heparin tubes (BD Vacutainer®, Becton Dickinson, Plymouth, UK) and rapidly centrifuged at 4,000 rpm and 4°C for 10 minutes. The plasma was then separated, frozen at -80°C until further analyses of nitrate and nitrite were performed. Non-stimulated saliva (3 milliliters) was also collected into a sterile falcon tube and rapidly frozen at -80°C. Then, nitrate and nitrite were measured in plasma and saliva using ozone-based chemiluminescence.
Change in oral nitrate-reducing capacity	7 days	Nitrate-reducing capacity of oral bacteria was analysed to compare vegetarians and omnivores and treatments (placebo mouthwash vs antibacterial mouthwash). Participants were instructed to hold 10 milliliters of water containing sodium nitrate (80 μicromols) in their mouth for 5 minutes. The mouth rinse was collected into a Falcon sterile tube and centrifuged (4,500 rpm, 4°C) for 10 minutes. The supernatant was collected and stored at -80°C before measuring absolute nitrite concentration.
Change in blood pressure	7 days	Systolic, diastolic and mean arterial blood pressure was measured following British Hypertension Guidelines. Three successive supine readings were taken using an oscillometric device (Connex ProBP 3400 Digital Blood Pressure Device, Welch Allyn UK Ltd.) with a one minute rest between readings. The second and third readings were averaged to determine mean clinic blood pressure.
Change in blood biomarkers	7 days	Blood markers were analyzed to assess differences between vegetarians and omnivores to control for diabetes and dyslipidaemia and to analyse the effect of antibacterial mouthwash.; Whole blood glucose and lactate was measured using a biochemistry analyser (YSI 2300 Stat Plus, YSI Life Sciences, USA). Total cholesterol, triglycerides, high density lipoproteins (HDL) and low density lipoproteins (LDL) were analysed with enzymatic methods using the Roche 702 spectrophotometric module of a Cobas 8000 analyser (Roche Diagnostics Ltd, UK)

Trial Locations

Locations (1)

Laboratory of Nutrition, Exercise & Health; 🇬🇧 Plymouth, Devon, United Kingdom