RecruitingInterventional

Sodium effect on aldosterone in real time

This study is investigating how a healthy person's aldosterone levels change over 24 hours when they eat different amounts of salt. Aldosterone is a hormone that can affect blood pressure, and sometimes too much of it can lead to high blood pressure. Currently, it's hard to tell if someone has too much aldosterone. By understanding how salt intake affects aldosterone in healthy people, researchers hope to improve how high blood pressure related to this hormone is diagnosed in the future. Participants will follow high and low salt diets and have their aldosterone levels measured to understand these changes.

At a glance

Status

Recruiting

Sponsor

University of Bristol

Enrolment target

Start

05 Oct 2025

Estimated completion

30 Apr 2027

Assessing whether altering dietary sodium intake affects the aldosterone pattern of a healthy individual over 24 hours.

What is this study about?

This study aims to understand how much the amount of salt you eat affects a hormone called aldosterone in healthy people. Aldosterone plays a role in controlling blood pressure, and sometimes, if someone has too much of this hormone, it can cause high blood pressure. Unfortunately, it's often difficult to find out if someone's high blood pressure is due to too much aldosterone because the current tests are complicated.

Researchers have developed a new device called U-Rhythm that can continuously monitor aldosterone levels. This device has already shown promise in identifying unusual aldosterone patterns. Before this new method can be used to help diagnose high blood pressure more effectively, we first need to understand how aldosterone levels naturally change in healthy people when their salt intake varies. This will help us compare these patterns with those of people who might have too much aldosterone.

By taking part, you'll help us learn valuable information about how our bodies regulate this important hormone in response to diet. This clearer picture of how aldosterone works in healthy individuals could pave the way for simpler and more accurate ways to diagnose certain types of high blood pressure, ultimately helping more people get the right treatment.

Key takeaways

This study explores how salt intake affects a blood pressure hormone called aldosterone in healthy people.
It could help improve diagnosis of certain types of high blood pressure in the future.
Participants will follow high and low salt diets, prepared by dietitians, for 7 days each.
Monitoring involves small skin probes for 24 hours, blood tests, urine collection, and light exercise.
Risks are minimal, mainly minor bruising; potential benefits include getting your test results.

Who may be eligible?

This study is looking for healthy adult volunteers, aged between 18 and 40 years old. Both men and women can take part. It's important that you don't have certain health conditions like high blood pressure, heart disease, or sleep apnoea.

You also can't be taking medications that might affect your hormone levels, including most medicines for high blood pressure or common inhalers. If a close family member (parent or sibling) was diagnosed with high blood pressure before age 60, or if they have a specific condition called primary hyperaldosteronism, you won't be able to join.

Other things that might mean you can't take part include being pregnant, having a BMI of 30 or higher, regularly drinking a lot of alcohol, smoking or vaping daily, or using recreational drugs. If you've worked night shifts recently, have very irregular sleep patterns, or have a fear of needles, you also won't be able to participate. We also need to be able to cater for your dietary needs within the study's meal plans and for you to understand instructions in English.

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 40 years old?
Do you have good general health, without conditions like high blood pressure or heart disease?
Do you avoid daily smoking, vaping, recreational drugs, or drinking a lot of alcohol (more than 28 units/week)?
Are you able to understand spoken and written English instructions?
Are you able to follow specific meal plans provided by the study?

Answer every question to see your result.

What does participation involve?

If you join this study, you will take part in two main study periods. For each period, you'll first follow a special diet for 7 days – either high salt or low salt. Don't worry, these diets are prepared by NHS dietitians and are balanced in all other nutrients.

After these 7 days, you'll come to the University of Bristol. Here, tiny probes will be gently placed just under your skin to continuously measure your aldosterone and other hormone levels for 24 hours. You'll also give a 24-hour urine sample, have some blood tests (while lying down and standing up), and your kidney function will be checked. During this time, you'll also be asked to do some exercise on a static bike, as physical activity can affect these hormones. After a break (called a 'washout period'), you'll repeat the whole process, this time following the other diet (low salt if you did high salt first, or vice versa). The total study duration for you will involve these two 7-day diet periods plus the two 24-hour monitoring visits, and the washout period in between.

Potential risks and benefits

A potential benefit of taking part is that you will receive the results of your tests. If anything unusual is found and you agree, we can share this information with your GP. Some people might also enjoy the fitness test on the static bike. This study is considered very low risk. You might experience some minor bruising or discomfort where the small probes are inserted under your skin, similar to a small scratch. The risk of infection from these probes is very small. Blood tests might also cause slight bruising or discomfort, but we will only take a small amount of blood. You have the right to withdraw from the study at any time without giving a reason.

Locations (2)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

NIHR Bristol Clinical Research Facility
City only
Bristol, United Kingdom
University Hospitals Bristol and Weston NHS Foundation Trust
City only
Bristol, United Kingdom

Common questions

What is aldosterone and why is it important?

Aldosterone is a hormone made by your body that helps control your blood pressure and the balance of salt and water in your body. Too much or too little can affect your health.

Will I have to prepare my own meals?

No, all the meals for your high and low salt diets will be prepared for you by NHS dietitians, ensuring they are balanced and meet the study requirements.

How long will the continuous monitoring last?

The continuous monitoring of your aldosterone levels using the special probes will last for 24 hours during each of your visits to the study centre.

Will I get paid for taking part?

The information provided does not mention payment for participation. You can ask the study contact for more details on this.

What happens if the study finds something unusual about my health?

If any of your test results show an abnormality and you agree, the study team will contact your GP to inform them of the finding.

How to find out more

Timothy Swinn

salt-study@bristol.ac.uk +44 (0)1173426691 Official trial record

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