Inter-individual Variation in the Blood Pressure Lowering Effects of Dietary Nitrate
Condition: Blood Pressure
Study type: Interventional

Summary: 
      Dietary nitrate supplementation, often in the form of beetroot juice, has been shown to lower
      blood pressure and could play a role in preventing or treating hypertension. However, it is
      currently unclear: a) how reproducible this response is within the same individual on
      different occasions, and b) whether there are genuine individual differences in the blood
      pressure lowering effects of dietary nitrate. This study will use a novel replicated
      cross-over design (2 x nitrate conditions, 2 x placebo conditions) to examine the
      reproducibility and inter-individual variability in the blood pressure lowering effects of
      dietary nitrate supplementation.
    

Detailed description: 
      The investigators will undertake a replicated cross-over randomised controlled trial (i.e., a
      study involving 2 x identical experimental conditions and 2 x identical control conditions),
      to explore the reproducibility of the blood pressure lowering effects of nitrate-rich
      beetroot juice, and to identify if there are genuine individual differences in the blood
      pressure-lowering effects of this supplement. Participants will be recruited via posters,
      email and social media, and interested individuals will be invited to attend the laboratory
      on 5 occasions.

      Visit 1: Potential participants will be invited to attend a screening session at Newcastle
      University to identify if they are eligible to participate. They will have an opportunity to
      discuss the study with a researcher and will provide written consent. They will then complete
      a screening questionnaire and provide a measure of their height, weight and blood pressure.
      Eligible participants will be invited to attend 4 experimental trials (2 x nitrate-rich
      beetroot juice conditions, 2 x placebo conditions) over 2-3 weeks with a minimum of 3 days
      wash-out between visits. If individuals are ineligible to participate this will be explained
      to them and they will be thanked for their time.

      Visits 2-5: On the day before the first trial, participants will be asked to record what they
      eat and then replicate this as closely as possible for all future visits. In the morning of
      each trial, participants will be asked to arrive at the laboratory between 7-9 am having
      fasted since 10 pm the night before. The participants will be required to rest for 10
      minutes, after which a measure of their blood pressure will be obtained. Participants will
      then be provided with breakfast (a bowl of porridge) and 140 ml concentrated nitrate-rich
      (~12.5 mmol nitrate) or nitrate-depleted beetroot juice (~0 mmol nitrate). Participants will
      then be asked to sit in the laboratory for 2.5 hours, during which time they can read quietly
      or use a computer. The investigators will then obtain a further measure of their blood
      pressure and collect a blood sample from a vein in their arm via venepuncture, to measure
      markers of nitric oxide, a signalling molecule in the body which is thought to mediate the
      blood pressure lowering effects of nitrate-rich beetroot juice.
    

Intervention name(s): Beet It Sport Shot; Beet It Sport Shot Placebo
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): Acute supplementation with 140 ml Beet It Sport Shots, James White Ltd, containing ~400mg dietary nitrate; Acute supplementation with 140 ml Beet It Sport Shots Placebo, James White Ltd, in which the nitrate has been removed via an ion exchange resin, containing ~ 0 mg dietary nitrate
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Replicated cross-over trial
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Hypertension; Personalized nutrition; Nitric oxide; Beetroot juice