Kefir versus milk for gut microbiome, sleep, and cardiometabolic markers
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
This project will test whether drinking 250 ml of kefir daily for 4 weeks, compared with milk, can improve gut bacteria, sleep quality, and LDL cholesterol in adults aged 40–70 with poor sleep and BMI 25–35.
Quick facts
| Phase | Not applicable |
|---|---|
| Study type | Interventional |
| Enrollment | 40 (estimated) |
| Ages | 40 Years to 70 Years |
| Sex | All |
| Sponsor | Sheffield Hallam University Academic / other |
| Locations | 2 sites (Leeds, West Yorkshire and 1 other locations) |
| Trial ID | NCT07071181 on ClinicalTrials.gov |
What this trial studies
In a randomised, double-blind, two-arm crossover design, 40 adults with poor sleep and BMI 25–35 will consume 250 ml of kefir or milk daily for 4 weeks followed by a 4-week washout before crossing over. The primary outcome is a 5% change in LDL cholesterol and secondary outcomes include gut microbiome composition, sleep quality and duration, cognitive function and mood, arterial stiffness, blood pressure, triglycerides, non-HDL cholesterol, inflammation, and immune markers. Stool, blood, and sleep measures will be collected at baseline and at the end of each intervention period, and drinks will be administered in counterbalanced order to minimise order effects. The trial was powered at 80% to detect small effects and aims to recruit 40 participants to allow for dropouts.
Who should consider this trial
Good fit: Ideal candidates are adults aged 40–70 with poor sleep (PSQI >5), BMI 25–35 kg/m2, no milk allergy, and ability to drink the test beverages daily and attend four laboratory visits.
Not a fit: People who are allergic or intolerant to milk, pregnant or breastfeeding, have gastrointestinal disorders, or are outside the age or BMI range are unlikely to benefit from this protocol.
Why it matters
Potential benefit: If successful, regular kefir consumption could modestly improve sleep and lower LDL and other cardiometabolic risk markers through beneficial changes in the gut microbiome.
How similar studies have performed: Small prior studies of kefir and other fermented foods have reported modest changes in gut microbiota and some lipid improvements, but results are limited and not yet conclusive.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: * 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 Exclusion Criteria: * 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
Where this trial is running
Leeds, West Yorkshire and 1 other locations
- University of Leeds — Leeds, West Yorkshire, United Kingdom (Not_yet_recruiting)
- College of Health, Wellbeing and Life Sciences — Sheffield, United Kingdom (Recruiting)
Study contacts
- Principal investigator: Tony Lynn, PhD — Sheffield Hallam University
- Study coordinator: Tony Lynn,, PhD
- Email: T.lynn@shu.ac.uk
- Phone: 0114 2252065
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.