Evaluation of the Effect of Kefir Consumption (Kefirness)

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

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.

Study Overview

• Status: Active, not recruiting
• Conditions: Well-being; Emotion
• Intervention / Treatment: Other: Consumption of a control beverage, non-fermented carbonated drink; Other: Consumption of fruit kefir; Other: Consumption of micro-filtered fruit kefir

Detailed Description

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.

• Study Type: Observational
• Enrollment (Estimated): 66

Contacts and Locations

Study Locations

• France
  • Montpellier, France
    • SYS2DIAG - UMR9005 CNRS/ALCEN, Montpellier, 34184

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Probability Sample

Study Population

A total of 66 subjects will be recruited on a voluntary basis :

• 22 subjects who will consume a control beverage, non-fermented carbonated drink (BRAS-C)
• 22 subjects who will consume fruit kefir (BRAS-F)
• 22 subjects who will consume micro-filtered fruit kefir (BRAS-P).

The distribution of subjects into the 3 BRAS will be carried out by a controlled randomized method.

Description

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.

Study Plan

How is the study designed?

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
BRAS-C; Consumption of a control beverage, non-fermented carbonated drink	Other: Consumption of a control beverage, non-fermented carbonated drink; 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.
BRAS-F; Consumption of fruit kefir	Other: Consumption of fruit kefir; 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.
BRAS-P; Consumption of micro-filtered fruit kefir	Other: Consumption of micro-filtered fruit kefir; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the effects of fruit kefir	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.	3 years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluate the effects of kefir on the well-being of participants	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.	3 years
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	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 years
Compare the rate of BCAAs in the urine and saliva	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.	3 years
Establish a correlation between the rate of BCAAs and the molecular signature established	Establish a correlation between the rate of BCAAs and the molecular signature established from the dosage of biological biomarkers linked to emotions.	3 years
Establish a correlation between the metabolic changes measured with the rate of BCAAs	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.	3 years
Establish a correlation between the molecular signature established from the dosage	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.	3 years

Collaborators and Investigators

• Sponsor: Sys2Diag
• Collaborators: Centre National de la Recherche Scientifique, France
• Investigators: Principal Investigator: Laurence MOLINA, PhD, Sys2Diag

Publications and helpful links

General Publications

• Renaud Debailly, Christophe Lavelle et Émilien Schultz, " Conserver un aliment vivant ", Techniques & Culture, 69 | 2018, URL : http://journals.openedition.org/tc/8971
• Laureys D,De Vuyst L
• Molina L,Santos Schneider F,Kahli M,Ouedraogo A,Alali M,Almosnino A,Baptiste J,Boulestreau J,Davy M,Houot-Cernettig J,Mountou T,Quenot M,Simphor E,Petit V,Molina F
• Pendon MD, Bengoa AA, Iraporda C, Medrano M, Garrote GL, Abraham AG. Water kefir: Factors affecting grain growth and health-promoting properties of the fermented beverage. J Appl Microbiol. 2022 Jul;133(1):162-180. doi: 10.1111/jam.15385. Epub 2021 Dec 20.
• Lopitz-Otsoa F, Rementeria A, Elguezabal N, Garaizar J. Kefir: a symbiotic yeasts-bacteria community with alleged healthy capabilities. Rev Iberoam Micol. 2006 Jun;23(2):67-74. doi: 10.1016/s1130-1406(06)70016-x.

Study record dates

Study Major Dates

• Study Start (Actual): June 4, 2024
• Primary Completion (Actual): June 11, 2025
• Study Completion (Estimated): June 11, 2027

Study Registration Dates

• First Submitted: March 26, 2026
• First Submitted That Met QC Criteria: April 3, 2026
• First Posted (Actual): April 13, 2026

Study Record Updates

• Last Update Posted (Actual): April 13, 2026
• Last Update Submitted That Met QC Criteria: April 3, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Biomarkers; Probiotic; Kefir; Related
• Other Study ID Numbers: 2023-A02587-38; 24.00472.000223 (Other Identifier: Comité de protection des personnes (French Ethics committee))

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No