AdultSPIN-BP-NONCT07665944
Hydroponic vs Conventional Spinach Smoothies: Effects on Salivary Nitrate Bioavailability and Blood Pressure
A study testing Hydroponic spinach smoothie and Conventional spinach smoothie in people with Adult, run by University of Plymouth at 1 site in United Kingdom.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 to 60 yearsHealthy volunteers can take part
- Conditions the study is for
- Adult
- What is being tested?
- Hydroponic spinach smoothie and Conventional spinach smoothie
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 12 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 22 May 2026to 31 Jul 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 60 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- 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
Who cannot join
- 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
Show all 9Show fewer
- 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
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United Kingdom1 site, 1 recruiting
- Recruiting
University of Plymouth
Plymouth, Devon, PL4 6AB
Raul Bescos, PhD, +44 1752 587585, raul.bescos@plymouth.ac.uk
Patricia Casas Agustench, PhD, +44 1752 588892, patricia.casas@plymouth.ac.uk
About this study
Official title: Acute Effects of Hydroponically vs. Conventionally Grown Spinach Smoothies on Salivary Nitrate Bioavailability and Blood Pressure: A Randomized Controlled Crossover Trial
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:
Read more
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).
Read the detailed description
This randomized, double-blind, crossover study will investigate the acute effects of hydroponic spinach (HS) compared with conventional spinach (CS) smoothies on vascular responses in adults. The study aims to determine whether HS and CS smoothies elicit differential effects on nitrate bioavailability and blood pressure.
Spinach is a rich source of dietary nitrate, which can be converted via the enterosalivary pathway to nitrite and subsequently to nitric oxide, a key regulator of vascular function and blood pressure. The nitrate content of spinach varies according to cultivation methods, with hydroponically grown spinach often reported to have higher nitrate concentrations than conventionally grown spinach. However, it remains unclear whether these compositional differences translate into meaningful physiological effects following consumption.
Participants will attend two laboratory visits separated by a washout period of approximately 7-14 days. In this randomized crossover design, each participant will receive both interventions in a randomized order, enabling within-subject comparisons. At each visit, participants will consume a standardized smoothie containing either hydroponic or conventional spinach. The smoothies will be matched for volume and appearance to maintain blinding of both participants and investigators.
Baseline measurements will be obtained prior to smoothie consumption. Following intake, measurements will be repeated over the acute postprandial period, including at 2 hours post-consumption, to assess physiological responses. These assessments will include saliva samples to evaluate nitrate bioavailability (salivary nitrate) and cardiovascular measures-systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), and heart rate (HR).
The crossover design allows each participant to act as their own control, thereby reducing inter-individual variability and improving statistical power in this pilot investigation.
- Conditions
- Adult
- Being tested
- Hydroponic spinach smoothie, Conventional spinach smoothie
- Keywords
- spinach, Hydroponic agriculture, Conventional agriculture, Dietary nitrate, Nitrite, Nitric oxide, Blood pressure, Crossover study, Randomized controlled trial, Smoothie intervention, Postprandial response, Saliva biomarkers, Nitrate bioavailability
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Hydroponic spinach smoothieOther
Standardized smoothie prepared with hydroponically grown spinach, matched for volume and appearance.
Conventional spinach smoothieOther
Standardized smoothie prepared with conventionally grown spinach, matched for volume and appearance.
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: Other: Hydroponic spinach smoothie; Other: 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. Receives: Other: Hydroponic spinach smoothie; Other: Conventional spinach smoothie |
What is being measured
The primary outcome is the main question the study is designed to answer.
Salivary nitrate concentration
Salivary nitrate levels assessed at baseline and 2 hours post-consumption as a marker of nitrate bioavailability.
Measured: Baseline and 2 hours post-consumption
Secondary outcomes (4)
Systolic blood pressure
Systolic blood pressure measured at baseline and 2 hours after consumption of hydroponic and conventional spinach smoothies.
Measured: Baseline and 2 hours post-consumption
Diastolic blood pressure
Diastolic blood pressure measured at baseline and 2 hours after consumption of hydroponic and conventional spinach smoothies.
Measured: Baseline and 2 hours post-consumption
Mean arterial pressure
Mean arterial pressure measured at baseline and 2 hours post-consumption.
Measured: Baseline and 2 hours post-consumption
Heart rate
Heart rate measured at baseline and 2 hours post-consumption.
Measured: Baseline and 2 hours post-consumption
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Jun 2026
- Study start22 May 2026
- Primary completion19 Jun 2026 (estimated)
- Study completion31 Jul 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (6)Papers the sponsor has linked to this study.
- Other trials for AdultStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 12 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Plymouth
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Raul Bescos, University of Plymouth
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07665944
- Sponsor's protocol ID
- 6910
- Acronym
- SPIN-BP-NO
- Status last verified
- Jun 2026
- First submitted
- 10 Jun 2026
- Last updated
- 24 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Publications
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.
PubMed 35871120Jackson 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.
PubMed 29506204Hosseini 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.
PubMed 37084661Bryan 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.
PubMed 36690137Blekkenhorst 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.
PubMed 29635489Bian 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.
PubMed 32503134
Study at a glance
From the registry record, last updated by the sponsor on 24 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Acute Effects of Hydroponically vs. Conventionally Grown Spinach Smoothies on Salivary Nitrate Bioavailability and Blood Pressure: A Randomized Controlled Crossover Trial
- ClinicalTrials.gov ID
- NCT07665944
- Acronym / sponsor ID
- SPIN-BP-NO / 6910
- Conditions
- Adult
- Keywords
- spinach, Hydroponic agriculture, Conventional agriculture, Dietary nitrate, Nitrite, Nitric oxide, Blood pressure, Crossover study
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 12 participants (estimated)
- Lead sponsor
- University of PlymouthUniversity, hospital or other
- Study start
- 22 May 2026 (actual)
- Primary completion
- 19 Jun 2026 (estimated)
- Study completion
- 31 Jul 2026 (estimated)
- First posted
- 24 Jun 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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).
Detailed description
This randomized, double-blind, crossover study will investigate the acute effects of hydroponic spinach (HS) compared with conventional spinach (CS) smoothies on vascular responses in adults. The study aims to determine whether HS and CS smoothies elicit differential effects on nitrate bioavailability and blood pressure.
Spinach is a rich source of dietary nitrate, which can be converted via the enterosalivary pathway to nitrite and subsequently to nitric oxide, a key regulator of vascular function and blood pressure. The nitrate content of spinach varies according to cultivation methods, with hydroponically grown spinach often reported to have higher nitrate concentrations than conventionally grown spinach. However, it remains unclear whether these compositional differences translate into meaningful physiological effects following consumption.
Participants will attend two laboratory visits separated by a washout period of approximately 7-14 days. In this randomized crossover design, each participant will receive both interventions in a randomized order, enabling within-subject comparisons. At each visit, participants will consume a standardized smoothie containing either hydroponic or conventional spinach. The smoothies will be matched for volume and appearance to maintain blinding of both participants and investigators.
Baseline measurements will be obtained prior to smoothie consumption. Following intake, measurements will be repeated over the acute postprandial period, including at 2 hours post-consumption, to assess physiological responses. These assessments will include saliva samples to evaluate nitrate bioavailability (salivary nitrate) and cardiovascular measures-systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), and heart rate (HR).
The crossover design allows each participant to act as their own control, thereby reducing inter-individual variability and improving statistical power in this pilot investigation.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Hydroponic then Conventional Spinach | Experimental | Other: Hydroponic spinach smoothie, Other: Conventional spinach smoothieParticipants consume a hydroponic spinach smoothie at the first visit followed by a conventional spinach smoothie at the second visit, separated by a washout period. |
| Conventional then Hydroponic Spinach | Experimental | Other: Hydroponic spinach smoothie, Other: Conventional spinach smoothieParticipants consume a conventional spinach smoothie at the first visit followed by a hydroponic spinach smoothie at the second visit, separated by a washout period. |
Who may qualify
- Ages
- 18 to 60 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (6 listed)
- 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
Key exclusion criteria (9 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Hydroponic spinach smoothieStandardized smoothie prepared with hydroponically grown spinach, matched for volume and appearance. | Other | Conventional then Hydroponic Spinach, Hydroponic then Conventional Spinach |
| Conventional spinach smoothieStandardized smoothie prepared with conventionally grown spinach, matched for volume and appearance. | Other | Conventional then Hydroponic Spinach, Hydroponic then Conventional Spinach |
Primary outcome
Salivary nitrate concentration
Time frame: Baseline and 2 hours post-consumption
Salivary nitrate levels assessed at baseline and 2 hours post-consumption as a marker of nitrate bioavailability.
4 secondary outcomes
Systolic blood pressure
Time frame: Baseline and 2 hours post-consumption
Diastolic blood pressure
Time frame: Baseline and 2 hours post-consumption
Mean arterial pressure
Time frame: Baseline and 2 hours post-consumption
Heart rate
Time frame: Baseline and 2 hours post-consumption
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Jun 2026.
- Background: PubMed 35871120Qadir 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.
- Background: PubMed 29506204Jackson 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.
- Background: PubMed 37084661Hosseini 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.
- Background: PubMed 36690137Bryan 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.
- Background: PubMed 29635489Blekkenhorst 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.
- Background: PubMed 32503134Bian 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.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Hydroponic spinach smoothie and Conventional spinach smoothie in people with Adult, run by University of Plymouth at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 24 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Raul Bescos, PhD (+44 1752 587585, raul.bescos@plymouth.ac.uk), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Salivary nitrate concentration (time frame: Baseline and 2 hours post-consumption). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07665944, which also lists 6 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Jun 2026.