SleepNCT07071181
Effects of Milk-based Drinks on Gut Microbiome, Sleep and Cardiometabolic Markers
A study testing Original flavour kefir and Milk in people with Sleep and Cardiovascular Diseases, run by Sheffield Hallam University at 2 sites in United Kingdom.
Trial summary
The purpose of this study is to evaluate the effects of kefir on gastrointestinal health, sleep quality, and biochemical parameters in adults who have sleep problems. Further measurements of cognitive function, arterial stiffness and blood pressure will also be assessed. Read more about this study
- Who is it for?
- Ages 40 to 70 yearsHealthy volunteers can take part
- Conditions the study is for
- Sleep, Cardiovascular Diseases, Gut Microbiome
- What is being tested?
- Original flavour kefir and Milk
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 40 participants
- Where
- 2 sitesUnited Kingdom
- Study dates
- Aug 2025to Mar 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 40 to 70 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Aged 40-70 years old
- Suffer with poor sleep (measured using the PIttsburg Sleep Quality Index with a score > 5)
- BMI in range of 25-35 kg/m2
- Willingness to consume each study drink daily for 4 weeks and attend the laboratory on 4 separate occasions
- For women: Medication in the form of contraception or HRT providing these have not been modified 3 months prior to the first study day
Who cannot join
- Intolerance or allergy to milk-based products
- Pregnancy/breastfeeding
- Insufficient English language skills to complete all study questionnaires and perform the cognitive tests
- Gastrointestinal disorders
- Inability to attend the laboratory due to travel/mobility difficulties
Trial locations and contacts
2 sites in 1 country. Contact the study team or a site near you to ask about taking part.
Lucy Ellis, PhD contact
United Kingdom2 sites, 2 recruiting
- Not yet recruiting
University of Leeds
Leeds, West Yorkshire, LS29JT
Professor Kieran Tuohy, 01133432876, k.tuohy@leeds.ac.uk
Dr Anthony Buckley, a.buckley1@leeds.ac.uk
- Recruiting
College of Health, Wellbeing and Life Sciences
Sheffield, S1 1WB
Tony Lynn, PhD, 0114 2252065, T.Lynn@shu.ac.uk
Lucy Ellis, PhD, Lucy.Ellis@shu.ac.uk
About this study
Official title: A Randomised, Double-blind Trial to Measure the Effects of Milk-based Drinks on Gut Microbiome, Sleep, and Cardiometabolic Markers in Adults With Poor Sleep
The purpose of this study is to evaluate the effects of kefir on gastrointestinal health, sleep quality, and biochemical parameters in adults who have sleep problems. Further measurements of cognitive function, arterial stiffness and blood pressure will also be assessed.
The following questions will be addressed during the study:
Read more
- What effect does repeated ingestion of kefir have on the gut microbiome and can this positively influence sleep performance (quality and duration) in adults with sleep problems?
- Does repeated ingestion of kefir impact LDL, triacyglycerols and non-HDLc in adults with sleep problems?
- What effect does repeated ingestion of kefir have on cognitive function and mood?
- What effect does repeated ingestion of kefir have on vascular function, inflammation and markers of immunity in adults with sleep problems?
In a randomised, crossover design study, participants will consume 250 ml of kefir (original flavour) or milk for 4 weeks with a 4-week washout.
Read the detailed description
The gut microbiome is recognized as a key regulator of host health, influencing various physiological processes. Dysbiosis of the gut microbiome has been implicated in a range of adverse health outcomes, including disruptions in sleep architecture and impairments in cardiometabolic function. There is growing interest in identifying dietary interventions that can modulate gut microbiota composition and functionality. In particular, the consumption of fermented foods, such as kefir, has emerged as a potential strategy for promoting microbial homeostasis and improving health outcomes
This study conforms to a randomised, double-blind 2-arm crossover design. Participants will consume either Kefir (original flavour) or milk. Each arm will involve daily consumption of the drink for 4-weeks with a 4 week washout before crossing over to the opposite condition. Drinks will be administered in a counterbalanced order to minimise potential order effects.
The primary outcome of this study is a 5% change in LDL based on a previous study (Bellikci-Koyu et al., 2022).
Assuming type I error probability α = 0.05 and power of 80%, and effect size of 0.2 G*power calculated that 32 participants would need to be recruited.
To account for potential drop out and balanced randomization, we will aim to recruit 40 participants.
Participants will be recruited through the use of posters around Sheffield Hallam University and the University of Leeds, through emails to staff and students, and contacts at surrounding universities. Potentially eligible participants will be identified through the use of a recruitment questionnaire before being invited to a screening visit for full consideration for the study. All participants will provide written informed consent before participating.
A linear mixed model analysis will be used to assess the effect of kefir on outcome parameters.
- Conditions
- Sleep, Cardiovascular Diseases, Gut Microbiome, Cognitive Function and Mood, LDL Cholesterol
- Being tested
- Original flavour kefir, Milk
- Medical subject headings
- Cardiovascular Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Original flavour kefirDietary supplement
Participants will consume 250ml of original flavour kefir daily for 4 weeks. According to the manufacturer, "packed with billions of live cultures to support Gut health".
MilkOther
Participants will consume 250 ml milk daily for 4 weeks. This milk will not contain any live cultures.
| Study group | Role | What they receive |
|---|---|---|
| Original Kefir | Active comparator | 250ml of original kefir Receives: Dietary Supplement: Original flavour kefir |
| Milk | Sham comparator | 250 ml of milk Receives: Other: Milk |
What is being measured
The primary outcome is the main question the study is designed to answer.
LDL Cholesterol
A blood sample via venepuncture will be taken at baseline and again after 4-weeks of daily consumption of the intervention or control for the assessment of LDL cholesterol. Blood samples will be obtained in a fasted state.
Measured: 4-weeks
Gut microbiome
A stool sample will be collected from participants at baseline and after 4 weeks daily consumption of the intervention and control drink. The composition of the microbiome in stool will be measured by 16s rRNA sequencing.
Measured: 4-weeks
Sleep quality and duration
Sleep quality and duration will be measured objectively and subjectively. For subjective measures, the Pittsburg Sleep Quality Index will be used to assess participant's sleep habits. The tool comprises of 7 sub-components and 18 items, including subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication and daytime dysfunction. In addition, the Epworth Sleepiness Scale. The Epworth sleepiness scale results range from 0 to 24.
Participants will also wear a Fitbit Charge 2 watch to track their sleep. Sleep measures will be obtained during the 7-day run in and final week of each study intervention for a total of 4 questionnaires to be completed by each participant and 4 week of objective sleep data.
Measured: 4-weeks
Secondary outcomes (5)
Blood samples
Serum or plasma samples will be obtained via venepuncture for the measurement of insulin, fasting blood glucose, lipids (LDL, HDL), triglycerides, iCAM, vCAM, CRP, and IL-6. All measurements will be taken in a fasted state at each intervention day.
Measured: 4-weeks
Cognitive function
A cognitive test battery consisting of 3 cognitive tests will be used to investigate the effect of the intervention or control on cognitive function. Participants mood will also be assessed using the Positive and Negative Affect Schedule (PANAS) questionnaire that asks participants to rate a series of adjectives describing both positive and negative emotions.
Measured: 4 weeks
Blood pressure
Blood pressure (systolic blood pressure, diastolic blood pressure and heart rate) will be measured in triplicate using a Vicorder after the paritipcant has rested for 15 minutes upon arrival to the lab. All measurements will be taken in a fasted state.
Measured: 4 week
Pulse Wave Analysis
Carotid to femoral Pulse Wave Velocity (PWV) and Augmentation Index (Aix) will be measured using a Vicorder.
Measured: 4 week
Saliva IgG
Participants will be asked to provide a saliva sample after a 10 minute mouth rinse with water. Saliva samples will be analysed for IgA using ELISA.
Measured: 4 week
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted17 Jul 2025
- Study startAug 2025 (estimated)
- Primary completionMar 2026 (estimated)
- Study completionMar 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for SleepStudies 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
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- This trial conforms to a randomised, double-blind, 2 arm crossover. Participants will consume the active drink or a control drink for 4 weeks before crossing over to the opposite condition after a 4-week washout. Order of drink allocation will be counterbalanced.
- Masking
- Triple blind
- Who is masked
- Participant, Investigator, Outcomes assessor
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Sheffield Hallam University
- Sponsor type
- University, hospital or other
- Collaborators
- Biotiful, University of Leeds, Nimble Science Ltd.
- Responsible party
- Principal investigator, Tony Lynn, Sheffield Hallam University
- Investigators
- Tony Lynn, PhD, Principal investigator, Sheffield Hallam University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07071181
- Sponsor's protocol ID
- ER72870766
- Other IDs
- Other
- Status last verified
- Jun 2025
- First submitted
- 9 Jul 2025
- Last updated
- 17 Jul 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 17 Jul 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Randomised, Double-blind Trial to Measure the Effects of Milk-based Drinks on Gut Microbiome, Sleep, and Cardiometabolic Markers in Adults With Poor Sleep
- ClinicalTrials.gov ID
- NCT07071181
- Acronym / sponsor ID
- ER72870766
- Conditions
- Sleep, Cardiovascular Diseases, Gut Microbiome, Cognitive Function and Mood, LDL Cholesterol
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- Sheffield Hallam UniversityUniversity, hospital or other
- Collaborators
- Biotiful, University of Leeds, Nimble Science Ltd.
- Study start
- Aug 2025 (estimated)
- Primary completion
- Mar 2026 (estimated)
- Study completion
- Mar 2026 (estimated)
- First posted
- 17 Jul 2025 (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 purpose of this study is to evaluate the effects of kefir on gastrointestinal health, sleep quality, and biochemical parameters in adults who have sleep problems. Further measurements of cognitive function, arterial stiffness and blood pressure will also be assessed.
The following questions will be addressed during the study:
- What effect does repeated ingestion of kefir have on the gut microbiome and can this positively influence sleep performance (quality and duration) in adults with sleep problems?
- Does repeated ingestion of kefir impact LDL, triacyglycerols and non-HDLc in adults with sleep problems?
- What effect does repeated ingestion of kefir have on cognitive function and mood?
- What effect does repeated ingestion of kefir have on vascular function, inflammation and markers of immunity in adults with sleep problems?
In a randomised, crossover design study, participants will consume 250 ml of kefir (original flavour) or milk for 4 weeks with a 4-week washout.
Detailed description
The gut microbiome is recognized as a key regulator of host health, influencing various physiological processes. Dysbiosis of the gut microbiome has been implicated in a range of adverse health outcomes, including disruptions in sleep architecture and impairments in cardiometabolic function. There is growing interest in identifying dietary interventions that can modulate gut microbiota composition and functionality. In particular, the consumption of fermented foods, such as kefir, has emerged as a potential strategy for promoting microbial homeostasis and improving health outcomes
This study conforms to a randomised, double-blind 2-arm crossover design. Participants will consume either Kefir (original flavour) or milk. Each arm will involve daily consumption of the drink for 4-weeks with a 4 week washout before crossing over to the opposite condition. Drinks will be administered in a counterbalanced order to minimise potential order effects.
The primary outcome of this study is a 5% change in LDL based on a previous study (Bellikci-Koyu et al., 2022).
Assuming type I error probability α = 0.05 and power of 80%, and effect size of 0.2 G*power calculated that 32 participants would need to be recruited.
To account for potential drop out and balanced randomization, we will aim to recruit 40 participants.
Participants will be recruited through the use of posters around Sheffield Hallam University and the University of Leeds, through emails to staff and students, and contacts at surrounding universities. Potentially eligible participants will be identified through the use of a recruitment questionnaire before being invited to a screening visit for full consideration for the study. All participants will provide written informed consent before participating.
A linear mixed model analysis will be used to assess the effect of kefir on outcome parameters.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Triple blind (participant, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- This trial conforms to a randomised, double-blind, 2 arm crossover. Participants will consume the active drink or a control drink for 4 weeks before crossing over to the opposite condition after a 4-week washout. Order of drink allocation will be counterbalanced.
| Arm | Type | Receives |
|---|---|---|
| Original Kefir | Active comparator | Dietary Supplement: Original flavour kefir250ml of original kefir |
| Milk | Sham comparator | Other: Milk250 ml of milk |
Who may qualify
- Ages
- 40 to 70 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Aged 40-70 years old
- Suffer with poor sleep (measured using the PIttsburg Sleep Quality Index with a score > 5)
- BMI in range of 25-35 kg/m2
- Willingness to consume each study drink daily for 4 weeks and attend the laboratory on 4 separate occasions
- For women: Medication in the form of contraception or HRT providing these have not been modified 3 months prior to the first study day
Key exclusion criteria (5 listed)
- Intolerance or allergy to milk-based products
- Pregnancy/breastfeeding
- Insufficient English language skills to complete all study questionnaires and perform the cognitive tests
- Gastrointestinal disorders
- Inability to attend the laboratory due to travel/mobility difficulties
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 |
|---|---|---|
| Original flavour kefirParticipants will consume 250ml of original flavour kefir daily for 4 weeks. According to the manufacturer, "packed with billions of live cultures to support Gut health". | Dietary supplement | Original Kefir |
| MilkParticipants will consume 250 ml milk daily for 4 weeks. This milk will not contain any live cultures. | Other | Milk |
Primary outcome
LDL Cholesterol
Time frame: 4-weeks
A blood sample via venepuncture will be taken at baseline and again after 4-weeks of daily consumption of the intervention or control for the assessment of LDL cholesterol. Blood samples will be obtained in a fasted state.
Gut microbiome
Time frame: 4-weeks
A stool sample will be collected from participants at baseline and after 4 weeks daily consumption of the intervention and control drink. The composition of the microbiome in stool will be measured by 16s rRNA sequencing.
Sleep quality and duration
Time frame: 4-weeks
Sleep quality and duration will be measured objectively and subjectively. For subjective measures, the Pittsburg Sleep Quality Index will be used to assess participant's sleep habits. The tool comprises of 7 sub-components and 18 items, including subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication and daytime dysfunction. In addition, the Epworth Sleepiness Scale. The Epworth sleepiness scale results range from 0 to 24. Participants will also wear a Fitbit Charge 2 watch to track their sleep. Sleep measures will be obtained during the 7-day run in and final week of each study intervention for a total of 4 questionnaires to be completed by each participant and 4 week of objective sleep data.
5 secondary outcomes
Blood samples
Time frame: 4-weeks
Cognitive function
Time frame: 4 weeks
Blood pressure
Time frame: 4 week
Pulse Wave Analysis
Time frame: 4 week
Saliva IgG
Time frame: 4 week
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 17 Jul 2025.
- Individual participant dataSharing planned: No
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Healthy Adult Participants
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.
Lucy Ellis, PhD contact
Tony Lynn, PhD principal investigator
Sheffield Hallam University
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Original flavour kefir and Milk in people with Sleep and Cardiovascular Diseases, run by Sheffield Hallam University at 2 sites 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 5 inclusion and 5 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 17 Jul 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites 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. Some participants in this study may receive a placebo. 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 Tony Lynn,, PhD (0114 2252065, T.lynn@shu.ac.uk), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
LDL Cholesterol (time frame: 4-weeks). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 17 Jul 2025.