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Active, Not Recruiting

NCT Number: NCT07522372

Evaluation of the Effect of Kefir Consumption

Many societies traditionally use fermentation as a means of producing beverages, whose microbial transformation is spontaneously triggered or facilitated by the addition of a catalyst (yeasts, bacteria). Kefir is a traditional beverage belonging to the latter category.

It is a probiotic that is supposed to modify the intestinal microbiota and the metabolites produced.

Links between kefir and metabolic syndromes (insulin resistance, etc.) have also been described in animal models. Very few clinical studies have evaluated the effects of kefir in humans.

A 'positive feeling' has also been described by people who consume kefir. Kefir could therefore have an effect on people's well-being.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

Key information

Conditions

Emotion Well-Being

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Observational

Primary location

SYS2DIAG - UMR9005 CNRS/ALCEN, Montpellier, 34184

Montpellier, France

About this study

Many societies traditionally use fermentation as a means of producing beverages, whose microbial transformation is spontaneously triggered or facilitated by the addition of a catalyst (yeasts, bacteria). Kefir is a traditional beverage belonging to the latter category. This beverage is obtained by inoculating sugared water, supplemented with fresh and dried fruits, with translucent grains composed of symbiotic microorganism communities (mainly lactic acid bacteria and yeasts). Kefir conveys an image of a 'healthy' beverage, naturally sparkling and non-alcoholic (alcohol content <1%), rich in probiotics), which undoubtedly explains the enthusiasm it generates among consumers.

The traditional nature of kefir lies in the use of fresh kefir grains as the sole ferment, passed down from producer to producer over generations.

Kefir is a probiotic that is supposed to modify the intestinal microbiota and the metabolites produced. Recent studies have described positive health effects of kefir. These effects could be exerted by a combination of live microorganisms contained in the fermented beverage, as well as by the bioactive components released in foods as by-products of the fermentation process. Links between kefir and metabolic syndromes (insulin resistance, etc.) have also been described in animal models. Very few clinical studies have evaluated the effects of kefir in humans. Branched-chain amino acids (BCAAs) are provided by the diet and are essential to the human body. They are also markers of insulin resistance. Measuring metabolites such as BCAAs in biofluids would verify if kefir has an effect on food degradation and thus on the intake of essential amino acids. This information is important both to better understand the mechanism of action of kefir and its effects on the production of metabolites such as BCAAs.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Subject aged between 18 and 65 years
  • Subject agreeing to follow the study procedures
  • Subject capable of understanding the purpose, nature, and methodology of the study
  • Subject having signed the informed consent
  • Subject who has never regularly consumed kefir and/or kombucha.

Exclusion criteria

  • Pregnant or breastfeeding woman
  • Subject not affiliated with a French Social Security scheme or not a beneficiary of such a scheme
  • Subject deprived of liberty, protected adults, vulnerable persons, or minors
  • Refusal to sign the consent to participate in the research
  • Subject who has already regularly consumed kefir and/or kombucha
  • Subject with confirmed diabetes

Criteria for Discontinuation of Participation in the Research :

  • Withdrawal of consent to participate in the research
  • Investigator's decision
  • Occurrence of a non-inclusion criterion.

Treatment and study plan

Consumption of a control beverage, non-fermented carbonated drink

Other

Consumption of a control beverage, non-fermented carbonated drink and measurement of the concentrations of metabolites such as BCAAs (valine, leucine, and isoleucine) in the biofluids (urine and saliva) of subjects, before and after regular consumption of fruit kefir.

Consumption of fruit kefir

Other

Consumption of fruit kefir and measurement of the concentrations of metabolites such as BCAAs (valine, leucine, and isoleucine) in the biofluids (urine and saliva) of subjects, before and after regular consumption of fruit kefir.

Consumption of micro-filtered fruit kefir

Other

Consumption of micro-filtered fruit kefir and measurement of the concentrations of metabolites such as BCAAs (valine, leucine, and isoleucine) in the biofluids (urine and saliva) of subjects, before and after regular consumption of fruit kefir.

Primary outcomes

  1. Evaluate the effects of fruit kefir

    Time frame: 3 years

    Evaluate the effects of fruit kefir on the release of amino acids such as BCAAs and more generally of metabolites in human biofluids (urine and saliva).

    The measurement of the concentrations of metabolites such as BCAAs (valine, leucine, and isoleucine) carried out in the biofluids (urine and saliva) of subjects, before and after regular consumption of fruit kefir using IDIR enzymatic dosage kit for BCAAs in a urine sample (SkillCell, France) according to the supplier's instructions. The concentrations are expressed in µM.

Secondary outcomes

  1. Evaluate the effects of kefir on the well-being of participants

    Time frame: 3 years

    Evaluate the effects of kefir on the well-being of participants who regularly consume this beverage, by measuring molecular biomarkers linked to the emotions felt. The levels of four biomarkers of interest (cortisol, alpha-amylase, DHEA, and oxytocin) will be measured in the saliva of participating subjects using enzymatic dosage methods or ELISA-type methods carried out using commercial kits. Concentrations are expressed in pM for cortisol and oxytocin, in U/mL for alpha-amylase, and in nM for DHEA.

  2. Compare the signatures of these molecular biomarkers in the saliva of subjects who consume different types of kefir preparations and subjects who consume a non-alcoholic carbonated placebo beverage

    Time frame: 3 years

    The comparison of the signatures of the biomarkers (cortisol, DHEA, oxytocin abd lapha amylase) in the saliva of subjects who consume fruit kefir, micro-filtered fruit kefir, or a non-alcoholic carbonated control beverage. Saliva samples are collected before and after consuming kefir. The baseline concentrations of biomarkers observed prior to kefir consumption revealed relatively high inter-individual variability. To account for the above and differing units of measurement, biomarker values are expressed as ratios following kefir consumption relative to the baseline value (prior to kefir consumption), thereby enabling comparisons on a consistent scale. Emotional assessments will be performed using a questionnaire.

    The variation profiles of the four biomarkers will be associated to emotional profiles induced by the drinks.

  3. Compare the rate of BCAAs in the urine and saliva

    Time frame: 3 years

    Compare the rate of BCAAs in the urine and saliva of subjects who consume different types of kefir preparations and subjects who consume a non-alcoholic carbonated placebo beverage.

  4. Establish a correlation between the rate of BCAAs and the molecular signature established

    Time frame: 3 years

    Establish a correlation between the rate of BCAAs and the molecular signature established from the dosage of biological biomarkers linked to emotions.

  5. Establish a correlation between the metabolic changes measured with the rate of BCAAs

    Time frame: 3 years

    Establish a correlation between the metabolic changes measured with the rate of BCAAs and the evaluation of the feelings of consumers according to other criteria such as questionnaires (self-assessment) for example.

  6. Establish a correlation between the molecular signature established from the dosage

    Time frame: 3 years

    Establish a correlation between the molecular signature established from the dosage of biological biomarkers of emotions and the evaluation of the well-being of consumers according to other criteria such as questionnaires (self-assessment) for example.

Sponsors and collaborators

Lead sponsor

Sys2Diag

Other Gov

Collaborators

  • Centre National de la Recherche Scientifique, France

Registry information

Official study title

Evaluation of the Effect of Kefir Consumption on Urinary and Salivary Levels of Metabolites Such as BCAAs and on Biomarkers of Well-being

Acronym: Kefirness

Important dates

Study start
2024
Primary completion
2025
Study completion
2027
First posted
Apr 13, 2026
Registry last updated
Apr 13, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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