Effects of Milk-based Drinks on Gut Microbiome, Sleep and Cardiometabolic Markers

Launched by SHEFFIELD HALLAM UNIVERSITY · Jul 9, 2025

Keywords

ClinConnect Summary

This clinical trial is studying how drinking kefir, a milk-based fermented drink, might affect gut health, sleep quality, heart health, thinking skills, and mood in adults who have trouble sleeping. The researchers want to see if drinking kefir every day can improve the balance of bacteria in the gut, help people sleep better, lower certain fats and cholesterol in the blood, and positively influence brain function and mood. They will also look at how kefir affects blood flow, inflammation, and the immune system.

To take part, you need to be between 40 and 70 years old, have poor sleep as measured by a simple questionnaire, and have a body weight that falls within a specific range. Participants will be asked to drink 250 ml of either kefir or regular milk every day for 4 weeks, then take a break for 4 weeks before switching to the other drink. During the study, you’ll visit the lab four times for tests and assessments. People who are allergic to milk, pregnant, breastfeeding, have certain gut problems, or can’t attend the visits won’t be able to join. This study is currently looking for volunteers who meet these criteria.

Gender

ALL

Eligibility 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