This study aims to investigate the effects of different dietary nitrate supplements, versus placebo, on microbiological and immunological markers associated with oral health in people aged 18-65 years. The main research questions are: * How do different dietary nitrate supplements (beetroot crystals vs. beetroot juice) affect oral health markers, including salivary pH and oral microbiome composition? * What is the acceptability and ease of integrating one of dietary nitrate supplements, made from beetroot but processed as freeze dried crystals or juice, into the daily diet? To answer these questions, the study will compare results from three groups of participants, who will be randomly assigned to one of the following study arms: Group 1: The control group will consume a placebo beetroot supplement completely free of nitrate in juice form. Group 2: The beetroot juice group will consume a beetroot supplement standardised to contain \~ 400 mg of nitrate in juice form. Group 3: The beetroot crystals group will consume a beetroot supplement standardised to contain \~400 mg of nitrate in freeze dried crystal form. The study will follow a randomised, single-blind, placebo-controlled, parallel design, and the intervention will last for four weeks. Data will be collected by providing pre- and post-intervention saliva samples tongue swabs, and various questionnaires will be completed at baseline and at the end of the study. In addition, at the end of the second week of the intervention period, participants will be asked to collect a saliva sample over three consecutive days at home.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Enrollment
60
The control group will consume a placebo supplement, entirely free of nitrate, in the form of juice (70 ml) for four weeks while maintaining their habitual diet.
The juice group will consume a beetroot supplement enriched with \~400 mg of nitrate in juice form (70 ml) for four weeks while maintaining their habitual diet.
The crystals group will consume a beetroot supplement enriched with \~400 mg of nitrate in crystals form (20g) for four weeks while maintaining their habitual diet.
Newcastle University, Newcastle upon Tyne, Tyne and Wear NE2 4HH
Newcastle, United Kingdom
RECRUITINGSaliva pH
Prior to and following the intervention, participants will provide an unstimulated saliva sample for pH measurement. The pH of each saliva sample will be measured using a pre-calibrated pH meter (±0.01 pH accuracy). Measurements will be performed in three independent replicates for each sample, with the three values recorded and then averaged. This average is used for the final pH value of the sample, helping to reduce the influence of random errors and improve the accuracy and reliability of the results. The device is recalibrated prior to measurements using standard calibration solutions to ensure accurate readings.
Time frame: 4 weeks
Oral microbiome
Prior to and following the intervention, participants will provide unstimulated saliva and tongue swab samples. DNA will be extracted from both the saliva and tongue swab samples, and 16S rRNA sequencing will be performed to identify and quantify changes in the oral microbiome.
Time frame: 4 weeks
Salivary nitrate/ nitrite concentrations
Prior to and following the intervention, participants will provide an unstimulated saliva sample to determine saliva nitrate and nitrite levels using ozone-based chemiluminescence. Home-collected saliva samples will also be analysed for three consecutive days to ensure compliance.
Time frame: 4 weeks
Saliva flow rate
Participants will provide an unstimulated saliva sample prior to and following the intervention. The saliva volume collected (in mL) will be divided by the time taken (in min) to obtain the flow rate in ml/min.
Time frame: 4 weeks
Salivary biomarkers
Participants will provide an unstimulated saliva sample prior to and following the intervention. If sufficient sample volume is available, exploratory analysis of salivary biomarkers related to inflammation may be considered.
Time frame: 4 weeks
Dry mouth severity (Xerostomia)
The impact of the study interventions on dry mouth symptom severity pre- and post-intervention will be assessed using the Summated Xerostomia Inventory-Dutch Version (SXI-D) questionnaire (Thomson et al., 2011), which has been validated in clinical and epidemiological research. Participants will provide information about their oral symptoms over the previous four weeks (e.g., feeling dry mouth or difficulty eating dry foods). Participants will be asked to select one of three options, each of which is associated with a score (Never (1); Occasionally (2) and Often, (3)). The SXI-D score range is 5-15, with higher scores indicating more severe dry mouth.
Time frame: 4 weeks
Oral hygiene behaviours
Participants will provide information on their oral hygiene behaviours before and after the intervention using the Oral Hygiene Behaviour Index questionnaire (Buunk-Werkhoven et al., 2011). The score ranges from 0 to 16, with a high total score indicating a high level of oral hygiene practices.
Time frame: 4 weeks
Dietary nitrate intake assessment
Before and after the intervention, participants will provide information about their intake of nitrate containing foods through a validated digital food frequency questionnaire(McMahon et al., 2023).
Time frame: 4 weeks
Intervention acceptability
The acceptability of the interventions will be assessed after the study is completed through a questionnaire designed to measure acceptability dimensions according to the Theoretical Framework of Acceptability (Sekhon et al., 2017), using a 5-point Likert scale to assess different aspects such as overall acceptability, palatability, and ease of use.
Time frame: 4 weeks
Participant Compliance
Compliance will be assessed using a participant-completed compliance log over a 4-week period. Participants will be asked to record: * The date and time of supplement intake. * How it was consumed. Additionally, any unused supplement sachets/bottles will be collected at the final visit to help estimate adherence.
Time frame: 4 weeks
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