NCT07665944

Brief Summary

The goal of this clinical trial is to determine whether hydroponic spinach (HS) versus conventional spinach (CS) smoothies produce differential post-consumption effects on salivary nitrate availability and blood pressure in adults. The main questions it aims to answer are: Do hydroponic spinach (HS) and conventional spinach (CS) smoothies produce differential post-consumption salivary nitrate availability responses in adults when consumed in equal volumes? Do hydroponic spinach (HS) and conventional spinach (CS) smoothies produce differential post-consumption blood pressure responses in adults when consumed in equal volumes? Participants will: Consume hydroponic spinach (HS) and conventional spinach (CS) smoothies on two separate study days. Attend two laboratory visits at the university, scheduled within a 1-2 week period. Undergo check-ups and study measurements during each visit (e.g., blood pressure and saliva sampling).

Trial Health

57
Monitor

Trial Health Score

Automated assessment based on enrollment pace, timeline, and geographic reach

Trial has exceeded expected completion date
Enrollment
12

participants targeted

Target at below P25 for not_applicable

Timeline
Completed

Started May 2026

Shorter than P25 for not_applicable

Geographic Reach
1 country

1 active site

Status
recruiting

Health score is calculated from publicly available data and should be used for screening purposes only.

Trial Relationships

Click on a node to explore related trials.

Study Timeline

Key milestones and dates

Study Start

First participant enrolled

May 22, 2026

Completed
19 days until next milestone

First Submitted

Initial submission to the registry

June 10, 2026

Completed
9 days until next milestone

Primary Completion

Last participant's last visit for primary outcome

June 19, 2026

Completed
5 days until next milestone

First Posted

Study publicly available on registry

June 24, 2026

Completed
1 month until next milestone

Study Completion

Last participant's last visit for all outcomes

July 31, 2026

Completed
Last Updated

June 24, 2026

Status Verified

June 1, 2026

Enrollment Period

28 days

First QC Date

June 10, 2026

Last Update Submit

June 18, 2026

Conditions

Adult

Keywords

spinachHydroponic agricultureConventional agricultureDietary nitrateNitriteNitric oxideBlood pressureCrossover studyRandomized controlled trialSmoothie interventionPostprandial responseSaliva biomarkersNitrate bioavailability

Outcome Measures

Primary Outcomes (1)

  • Salivary nitrate concentration

    Salivary nitrate levels assessed at baseline and 2 hours post-consumption as a marker of nitrate bioavailability.

    Baseline and 2 hours post-consumption

Secondary Outcomes (4)

  • Systolic blood pressure

    Baseline and 2 hours post-consumption

  • Diastolic blood pressure

    Baseline and 2 hours post-consumption

  • Mean arterial pressure

    Baseline and 2 hours post-consumption

  • Heart rate

    Baseline and 2 hours post-consumption

Study Arms (2)

Hydroponic then Conventional Spinach

EXPERIMENTAL

Participants consume a hydroponic spinach smoothie at the first visit followed by a conventional spinach smoothie at the second visit, separated by a washout period.

Other: Hydroponic spinach smoothieOther: Conventional spinach smoothie

Conventional then Hydroponic Spinach

EXPERIMENTAL

Participants consume a conventional spinach smoothie at the first visit followed by a hydroponic spinach smoothie at the second visit, separated by a washout period.

Other: Hydroponic spinach smoothieOther: Conventional spinach smoothie

Interventions

Hydroponic spinach smoothieOTHER

Standardized smoothie prepared with hydroponically grown spinach, matched for volume and appearance.

Conventional then Hydroponic SpinachHydroponic then Conventional Spinach
Conventional spinach smoothieOTHER

Standardized smoothie prepared with conventionally grown spinach, matched for volume and appearance.

Conventional then Hydroponic SpinachHydroponic then Conventional Spinach

Eligibility Criteria

Age18 Years - 60 Years
Sexall
Healthy VolunteersYes
Age GroupsAdult (18-64)

You may qualify if:

  • Adults aged 18-60 years
  • Generally healthy individuals (no diagnosed chronic disease)
  • Non-smokers and non-vapers
  • Not currently taking medications known to affect cardiovascular function or nitrate metabolism
  • Able and willing to provide informed consent
  • Willing to comply with study procedures and attend both study visits

You may not qualify if:

  • Presence of chronic disease (e.g., cardiovascular, metabolic, renal, or respiratory conditions)
  • Use of pacemakers or implanted medical devices
  • Pregnant or lactating individuals
  • Known allergy or intolerance to spinach
  • History of gastrointestinal disorders or pathology affecting digestion or absorption
  • Use of nitrate or nitrite supplements
  • Use of antibiotics within the past 3 weeks
  • Use of antibacterial mouthwash or oral products within the past 2 weeks
  • Current participation in another clinical trial or recent participation that may interfere with outcomes

Contact the study team to confirm eligibility.

Sponsors & Collaborators

Study Sites (1)

University of Plymouth

Plymouth, Devon, PL4 6AB, United Kingdom

RECRUITING

Related Publications (6)

  • Qadir OK, Seal CJ, Ashor AW, Tassotti M, Mena P, Del Rio D, Siervo M, Brandt K. Double-blind controlled dietary cross-over intervention with differentially fertilised intact lettuce leaves shows acute reduction in blood pressure in young adults, associated with faster uptake of nitrate than of phenolics. Eur J Nutr. 2022 Dec;61(8):4191-4203. doi: 10.1007/s00394-022-02961-5. Epub 2022 Jul 23.

    PMID: 35871120BACKGROUND

  • Jackson JK, Patterson AJ, MacDonald-Wicks LK, Oldmeadow C, McEvoy MA. The role of inorganic nitrate and nitrite in cardiovascular disease risk factors: a systematic review and meta-analysis of human evidence. Nutr Rev. 2018 May 1;76(5):348-371. doi: 10.1093/nutrit/nuy005.

    PMID: 29506204BACKGROUND

  • Hosseini MJ, Dezhangah S, Esmi F, S Gharavi-Nakhjavani M, Hashempour-Baltork F, Mirza Alizadeh A. A worldwide systematic review, meta-analysis and meta-regression of nitrate and nitrite in vegetables and fruits. Ecotoxicol Environ Saf. 2023 Jun 1;257:114934. doi: 10.1016/j.ecoenv.2023.114934. Epub 2023 Apr 19.

    PMID: 37084661BACKGROUND

  • Bryan NS, Ahmed S, Lefer DJ, Hord N, von Schwarz ER. Dietary nitrate biochemistry and physiology. An update on clinical benefits and mechanisms of action. Nitric Oxide. 2023 Mar 1;132:1-7. doi: 10.1016/j.niox.2023.01.003. Epub 2023 Jan 20.

    PMID: 36690137BACKGROUND

  • Blekkenhorst LC, Bondonno NP, Liu AH, Ward NC, Prince RL, Lewis JR, Devine A, Croft KD, Hodgson JM, Bondonno CP. Nitrate, the oral microbiome, and cardiovascular health: a systematic literature review of human and animal studies. Am J Clin Nutr. 2018 Apr 1;107(4):504-522. doi: 10.1093/ajcn/nqx046.

    PMID: 29635489BACKGROUND

  • Bian Z, Wang Y, Zhang X, Li T, Grundy S, Yang Q, Cheng R. A Review of Environment Effects on Nitrate Accumulation in Leafy Vegetables Grown in Controlled Environments. Foods. 2020 Jun 3;9(6):732. doi: 10.3390/foods9060732.

    PMID: 32503134BACKGROUND

Central Study Contacts

Raul Bescos, PhD

CONTACT

+44 1752 587585raul.bescos@plymouth.ac.uk

Patricia Casas Agustench, PhD

CONTACT

+44 1752 588892patricia.casas@plymouth.ac.uk

Study Design

Study Type
interventional
Phase
not applicable
Allocation
RANDOMIZED
Masking
TRIPLE
Who Masked
PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
Purpose
TREATMENT
Intervention Model
CROSSOVER
Sponsor Type
OTHER
Responsible Party
PRINCIPAL INVESTIGATOR
PI Title
Associate Professor of Human Nutrition and Physiology

Study Record Dates

First Submitted

June 10, 2026

First Posted

June 24, 2026

Study Start

May 22, 2026

Primary Completion

June 19, 2026

Study Completion

July 31, 2026

Last Updated

June 24, 2026

Record last verified: 2026-06

Locations

GB(1)