RecruitingInterventional

Investigating the impact of kefir on metabolic syndrome subjects in an inpatient setting

Researchers at Imperial College London are testing whether drinking kefir can improve gut health in adults with metabolic syndrome. Metabolic syndrome is a mix of health factors, like higher blood sugar and extra weight around the waist, which can raise the risk of diabetes and heart issues. Kefir is a traditional fermented milk drink packed with live, friendly bacteria. This study compares real kefir with a look-alike dummy drink with no active cultures. Because it is a 'crossover' trial, every participant will get to try both drinks at different times. Taking part involves two separate 4-day stays at Hammersmith Hospital in London. During your stays, the team will collect digestive samples using small, temporary tubes, as well as routine blood, urine, and stool samples. The findings will help scientists understand how everyday fermented foods might support long-term metabolic health.

At a glance

Status

Recruiting

Sponsor

Imperial College London

Enrolment target

Start

01 Aug 2026

Estimated completion

31 Mar 2027

Metabolic syndrome

What is this study about?

Trillions of tiny microbes live inside our digestive systems. These gut bacteria play a huge role in breaking down food, managing blood sugar, and keeping our bodies healthy. When the balance of these bacteria is disrupted, it can contribute to health challenges like weight gain, high blood pressure, and type 2 diabetes—a combination of factors often called metabolic syndrome.

Kefir is a sour, yoghurt-like drink made by fermenting milk with beneficial bacteria and yeasts. Many people drink it because they believe it supports digestion, but scientists still need clearer evidence on exactly how it works inside the human body. This clinical study aims to track what happens in the gut right after someone with metabolic syndrome drinks kefir.

By comparing kefir to an identical-tasting drink that contains no live bacteria, researchers can spot the exact changes kefir makes to gut bacteria and digestive hormones. This knowledge could help doctors give better, food-based advice to help people protect their heart health and blood sugar levels in the future.

Key takeaways

Tests how a fermented milk drink (kefir) affects gut bacteria in adults with metabolic syndrome.
Involves two separate 4-day hospital stays in London, plus short monthly check-ups.
Every participant tries both the real kefir drink and a dummy drink during the trial.
Includes collecting stomach, blood, urine, and stool samples to track your body's response.
Participation is entirely voluntary, and you can stop at any time without affecting your normal care.

Who may be eligible?

You may be able to take part if you are between 18 and 65 years old and have been diagnosed with metabolic syndrome. To join, you should currently eat a fairly low amount of fruit and vegetables (three portions or fewer a day) and rarely consume probiotic yoghurts, kefir, or live supplements (no more than three times a week).

You will not be able to join if you are lactose intolerant, follow a vegetarian or vegan diet, or are actively dieting to lose weight. People who are pregnant or breastfeeding, or who drink more than three alcoholic drinks a day, are also not eligible.

For safety reasons, you cannot take part if you have certain existing health conditions. These include type 1 diabetes, chronic gut conditions, active cancer, severe liver or kidney disease, or an implanted medical device like a pacemaker. You must also not have taken antibiotics in the month before the study.

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.

I am between 18 and 65 years old.
I have been diagnosed with metabolic syndrome (or have higher blood sugar and weight around the waist).
I can tolerate dairy products and do not have lactose intolerance.
I eat three or fewer portions of fruit and vegetables per day.
I rarely drink kefir or eat probiotic foods (no more than 3 times a week).
I am not currently pregnant, breastfeeding, or following a vegan or vegetarian diet.

Answer every question to see your result.

What does participation involve?

Taking part involves two separate 4-day inpatient stays at the NIHR Imperial Clinical Research Facility at Hammersmith Hospital in London. During each stay, you will receive either the real kefir drink or a matching dummy drink. You will also have a brief 2 to 3-hour check-up visit every month during the follow-up period.

While staying at the clinic, the medical team will use thin, temporary tubes passed into your stomach and small intestine to take samples as you digest the drink. You will also give regular blood, urine, and stool samples so the team can monitor changes in your body. The entire study is expected to run over approximately one year, starting in June 2026.

Potential risks and benefits

You may not get any direct medical benefit from joining this study, but your help will give scientists valuable insights into how healthy foods can prevent disease. The main risks are mild discomfort or small bruises from routine blood tests, and temporary gagging or throat irritation while the feeding tubes are placed. Placing the tubes uses a tiny amount of X-ray imaging, giving a radiation dose roughly equal to less than three months of natural background radiation in the UK. Taking part is completely voluntary, and you can change your mind and leave the trial at any time without giving a reason.

Locations (1)

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

NIHR Imperial Clinical Research Facility
City only
London, England

Common questions

What is kefir?

Kefir is a cultured, fermented milk drink similar to thin yoghurt. It is made using kefir grains, which add live, friendly bacteria and yeasts to the milk.

What is metabolic syndrome?

Metabolic syndrome is the medical term for having a cluster of related conditions together, such as extra weight around the tummy, high blood pressure, and higher blood fats or blood sugar.

Will I have to stay overnight at the hospital?

Yes. The study requires two separate 4-day inpatient stays at Hammersmith Hospital in London so the research team can closely monitor your digestion.

Will I definitely get the real kefir drink?

Yes, at some point. This is a crossover study, meaning every person who takes part will receive the real kefir drink during one stay and the dummy drink during the other.

Does taking part cost anything?

No, clinical trials do not charge participants. Research facilities often provide meals during inpatient stays and may offer help with reasonable travel expenses.

How to find out more

Isabel Garcia-Perez

i.garcia-perez@imperial.ac.uk +44 (0)7704344683 Official trial record

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