Effects of Kefir Consumption on Health Outcomes: Gastrointestinal System, Immunity, Biochemical Parameters, Body Composition, Sleep Quality and Mental Well Being in Healthy Adults

NCT06612164 | Completed

• 1 other identifier: 720
• Study Type: interventional
• Target: 65
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this clinical trial is to evaluate the effects of the administration of kefir on gastrointestinal system, mental health, biochemical parameters, immunity and inflammation processes as well as the sleep quality, elucidating the possible health effects of kefir consumption in healthy adults. The main questions it aims to answer are:

1. 1.Will be better the gastrointestinal system symptoms severity of volunteers in the intervention group will be better compared to the control group?
2. 2.Will be better the mental health status of volunteers in the intervention group will be better compared to the control group?
3. 3.Will be better the biochemical parameters of volunteers in the intervention group will be better compared to the control group?
4. 4.Will be better the immunity and inflammation processes of volunteers in the intervention group will be better compared to the control group?

Conditions

Effect of Kefir on Healthy Adults

Keywords

gastrointestinal symptoms; immunity; kefir; mental health; sleep quality; body composition

Outcome Measures

Primary Outcomes (4)

• Evaluation of Gastrointestinal Health

  Gastrointestinal Symptom Rating Scale developed by Revicki et al and validated in Turkish by Turan et al. (2017) was used to evaluate gastrointestinal health of participants. GSRS is a disease specific instrument comprising of 15 items combined into 5 symptom clusters namely abdominal pain (items 1, 4 and 5), reflux (items 2 and 3), indigestion (items 6, 7, 8 and 9), diarrhea (items 11,12 and 14) and constipation (items 10, 13 and 15). In order to score the items, participants state how he/she felt about these problems in the past week. GSRS questions are rated on a 7-point Likert scale ranging from \"no discomfort\" to \"very severe discomfort\". A score of 1 is given for the absence of symptoms, and 7 for frequent and severe symptoms. High scores indicate severity of symptoms and diseased state.

  From enrollment to the end of treatment at 6 weeks

• Body Composition and Anthropometric Measurements

  Body composition analysis, of the participants, was performed with TANITA MC-780 body composition analyser. By means of bioelectrical impedance analysis, basal metabolic rate and body composition (fat mass, muscle mass, fluid mass, lean mass, bone mineral mass, visceral fat, phase angle and edema index) were evaluated. Height (with SECA 206), body weight (with TANITA MC-780), neck and waist circumferences (with SECA 201) of participants were recorded. Heights were measured while standing upright and without shoes, feet were placed side by side, head was placed on the Frankfort Horizontal Plane, occipital region toucing the stadiometer. The body mass index (BMI) of the participants was calculated by dividing the body weight (kg) by the square the height (metres) and the evaluation was made according to the classification of the World Health Organization.

  From enrollment to the end of treatment at 6 weeks

• Mental Health

  The Warwick-Edinburgh Mental Well-Being Scale developed by Tennant et al. (2007) and validated in Turkish by Keldal (2015), was used to evaluate the mental health status of individuals. The WEMWBS total score is calculated by adding the scores assigned to each of the 14 items (1=never to 5=always). The minimum score that can be obtained is 14, whereas the maximum score obtained is 70. Higher scores are associated with higher mental well-being.

  From enrollment to the end of treatment at 6 weeks

• Immunity and Systemic-Inflammation

  Evaluation of immunity and systemic inflammation was performed using complete blood cell count and the SII, which is an important marker in reflecting inflammation and immune response. Although platelet-lymphocyte ratio (PLR) and neutrophil-lymphocyte ratio (NLR) are associated with disease activity, however, it has been suggested that SII, which is calculated by using platelet, neutrophil, and lymphocyte counts together, is a much more important marker in showing inflammation and immune response as compared to PLR and NLR values alone. Furthermore, SII is associated with various diseases such as cancer and cardiovascular disease. SII value is calculated with a formula (SII=P×N/L, P; platelet, N; neutrophil, L; lymphocyte) and high scores are associated with adverse health outcomes.

  From enrollment to the end of treatment at 6 weeks

Secondary Outcomes (3)

• Physical Activity

  From enrollment to the end of treatment at 6 weeks

• Biochemical Parameters

  From enrollment to the end of treatment at 6 weeks

• Dietary Patterns

  From enrollment to the end of treatment at 6 weeks

Other Outcomes (1)

• Sleep Quality

  From enrollment to the end of treatment at 6 weeks

Study Arms (2)

Kefir Consumption Group

EXPERIMENTAL

Commercial lactose-free kefir (Altinkilic, Turkey) beverage, which is produced from cow milk with 3.1% fat and 7.5% protein content and stored in appropriate conditions, was used in this study. The kefir (intervention) group was provided with 250 mL of plain lactose-free kefir containing at least 107-1010 probiotic bacterial strains (Lactobacillus, Lactic acid, Streptococcus, Acetic acid bacteria sp) and yeasts (Kluyveromyces marxianus, Torulaspora delbrueckii, Saccharomyces cerevisiae, Candida). The participants were asked to consume 250 mL of plain lactose-free kefir daily for 6 weeks. Any particular time was not specified for kefir consumption. Kefir consumption routine of participants was followed up by regular phone calls every week and evaluated by examining their consumption records.

Other: kefir

Control Group

NO INTERVENTION

Short Physical Activity Assessment Tool was used for evaluating physical activity levels of the participants, mental health status by The Warwick-Edinburgh Mental Well-Being Scale (WEMWBS). Gastrointestinal system symptoms were evaluated by using the Gastrointestinal Symptom Rating Scale (GSRS), sleep quality by the Pittsburg Sleep Quality Index (PSQI) and diet quality by the Healthy Eating Index-2015 (HEI-2015). Measurements were recorded prior to kefir intervention (initial measurement) and post kefir intervention (final measurement) for kefir and control groups.

Interventions

kefir OTHER

Commercial lactose-free kefir (Altinkilic, Turkey) beverage, which is produced from cow milk with 3.1% fat and 7.5% protein content and stored in appropriate conditions, was used in this study. The kefir (intervention) group was provided with 250 mL of plain lactose-free kefir containing at least 107-1010 probiotic bacterial strains (Lactobacillus, Lactic acid, Streptococcus, Acetic acid bacteria sp) and yeasts (Kluyveromyces marxianus, Torulaspora delbrueckii, Saccharomyces cerevisiae, Candida). The participants were asked to consume 250 mL of plain lactose-free kefir daily for 6 weeks. Any particular time was not specified for kefir consumption. Kefir consumption routine of participants was followed up by regular phone calls every week and evaluated by examining their consumption records. Those who consumed less than 85.0% (skipping kefir consumption maximum once a week) of the planned kefir consumption during the study period were excluded from the study.

Kefir Consumption Group

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Volunteer to consume 250 mL of plain lactose-free kefir once a day,
• Being healthy
• Being 18-35 years of age.

You may not qualify if:

• Follow a special diet for health reasons,
• Have an allergy to any food, have hepatic, renal and biliary diseases, have immunodeficiency, autoimmune and chronic gastrointestinal diseases, have a history of cancer, diabetes or cardiovascular diseases,
• Being pregnant/breastfeeding,
• Using vitamin-mineral and probiotic supplements,
• Using antibiotics in last one month and throughout the study period,
• Consuming probiotic foods or kefir on a regular basis,
• Smoking

Sponsors & Collaborators

• Medipol University: lead

Study Sites (1)

Istanbul Medipol University

Istanbul, Beykoz, 34815, Turkey (Türkiye)

Location

Related Publications (1)

• Bakirhan H, Ozyurek Arpa F, Pehlivan M, Kalkan I. Effects of Kefir Consumption on Gastrointestinal Health, Biochemical Parameters, Sleep, and Mental Well-Being in Healthy Young Adults: a Randomized Controlled Trial. J Nutr. 2026 Jan;156(1):101247. doi: 10.1016/j.tjnut.2025.11.016. Epub 2025 Nov 26.

  PMID: 41314291 DERIVED

MeSH Terms

Conditions

Psychological Well-Being; Sleep Initiation and Maintenance Disorders

Interventions

Kefir

Condition Hierarchy (Ancestors)

Personal Satisfaction; Behavior; Sleep Disorders, Intrinsic; Dyssomnias; Sleep Wake Disorders; Nervous System Diseases; Mental Disorders

Intervention Hierarchy (Ancestors)

Fermented Beverages; Beverages; Diet, Food, and Nutrition; Physiological Phenomena; Cultured Milk Products; Milk; Fermented Foods; Dairy Products; Food; Food and Beverages

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: OTHER
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: PhD

Study Record Dates

• First Submitted: September 23, 2024
• First Posted: September 25, 2024
• Study Start: February 1, 2023
• Primary Completion: June 30, 2023
• Study Completion: June 30, 2023
• Last Updated: September 25, 2024

Record last verified: 2024-09

Locations

TU (1)