RecruitingNAINTERVENTIONAL

Hydroponic vs Conventional Spinach Smoothies: Effects on Salivary Nitrate Bioavailability and Blood Pressure

Doctors are studying whether spinach grown in water (hydroponic) has different effects on your body compared to spinach grown in soil (conventional). Both types of spinach are known to contain good chemicals called nitrates, which can help with blood pressure. This study wants to find out if one type of spinach smoothie works better than the other after you drink it. Participants will visit the university twice to drink a spinach smoothie. We’ll carefully check their blood pressure and take saliva samples to measure these chemicals. This will help us understand if the farming method influences how spinach affects your health.

At a glance

Status

Recruiting

Phase

Sponsor

University of Plymouth

Enrolment target

Start

22 May 2026

Estimated completion

31 Jul 2026

Adult

What is this study about?

You might know that spinach is good for you, and one reason is that it contains natural substances called nitrates. When you eat spinach, your body can turn these nitrates into another useful chemical that helps your blood vessels work well and can affect your blood pressure. Recently, people have been growing spinach in new ways, like hydroponically (in water without soil). It's thought that hydroponic spinach might have even more of these helpful nitrates than spinach grown in the usual way.

This study wants to find out if this difference in how spinach is grown actually makes a difference to your body. Specifically, we're looking at whether drinking a smoothie made from hydroponic spinach affects your blood pressure and the levels of nitrates in your saliva differently compared to drinking a smoothie made from regular spinach. We want to see if the higher nitrate content that might be in hydroponic spinach really translates into a bigger benefit for your body.

By comparing these two types of spinach smoothies, the researchers hope to learn more about how different farming methods might change the health benefits of our food. This is an important step in understanding how what we eat can affect our blood pressure and overall health.

Key takeaways

This study compares two types of spinach smoothies: hydroponic (grown in water) and conventional (grown in soil).
We want to see if one type affects blood pressure and body chemicals (nitrates) more than the other.
Participants will visit the university twice for smoothie consumption and health checks.
The study involves checking blood pressure and saliva samples.
It helps us understand how farming methods might impact food's health benefits.

Who may be eligible?

This study is looking for healthy adults between 18 and 60 years old. You should not have any long-term illnesses like heart problems, diabetes, or kidney disease. It's also important that you don't smoke or vape.

There are a few other things that would mean you can't join. For example, if you're pregnant or breastfeeding, if you have any allergies to spinach, or if you've taken certain medications or mouthwashes recently. We also can't include anyone with a pacemaker or an implanted medical device.

The main idea is to make sure participants are generally healthy so we can clearly see the effects of the spinach smoothies without other health issues getting in the way.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you between 18 and 60 years old?
Are you generally healthy, with no long-term diseases?
Do you currently NOT smoke or vape?
Are you NOT pregnant or breastfeeding?
Do you NOT have an allergy to spinach?
Have you NOT used antibiotics in the last 3 weeks or antibacterial mouthwash in the last 2 weeks?

Answer every question to see your result.

What does participation involve?

If you decide to take part, you'll need to visit a university lab two times. These visits will be about one to two weeks apart. On each visit, you'll drink a smoothie: one time it will be a hydroponic spinach smoothie, and the other time it will be a conventional (regular) spinach smoothie. You won't know which one you're drinking on each visit.

During each visit, before and after you drink the smoothie, the research team will check your blood pressure and take some samples of your saliva. These measurements will help us understand how your body reacts to each smoothie. Each visit will involve these check-ups and will likely take a few hours. The total time you'd be involved in the study from your first visit to your last would be about two weeks.

Potential risks and benefits

Taking part in this study could help us learn more about how different types of spinach affect health, which could benefit many people in the future. You might also find it interesting to learn more about research. The study involves very low risk; the main things are drinking spinach smoothies, having your blood pressure taken, and providing saliva samples, which are generally safe procedures. There are no known serious risks associated with drinking spinach smoothies. You are free to withdraw from the study at any time, for any reason, without it affecting your medical care.

Locations (1)

University of Plymouth
Verified postcode
Plymouth, United Kingdom· Recruiting

Common questions

What is 'hydroponic' spinach?

Hydroponic spinach is grown using water-based nutrient solutions instead of soil.

Will I know which smoothie I'm drinking?

No, both you and the researchers won't know which smoothie type you're having on each visit. This is to keep the study fair.

What kind of checks will be done?

We'll be checking your blood pressure and taking small samples of your saliva during your visits.

Do I have to do anything special before my visits?

Yes, you might need to avoid certain foods, drinks, or mouthwashes before your visits. Specific instructions will be given if you join.

How long will each visit take?

Each visit will likely take a few hours to complete all the measurements before and after the smoothie.

How to find out more

Raul Bescos, PhD

raul.bescos@plymouth.ac.uk +44 1752 587585 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.