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. Will be better the gastrointestinal system symptoms severity of volunteers in the intervention group will be better compared to the control group? 2. Will be better the mental health status of volunteers in the intervention group will be better compared to the control group? 3. Will be better the biochemical parameters of volunteers in the intervention group will be better compared to the control group? 4. Will be better the immunity and inflammation processes of volunteers in the intervention group will be better compared to the control group? 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.
In order to evaluate the general characteristics, history of diseases and nutritional behaviors, a face-to-face questionnaire was conducted on all participants by the researchers. The questionnaire form contained information about the demographic information (age, gender, educational status, marital status, etc.), history of diseases (diagnosed diseases, drugs used etc.), basic nutritional habits (number of major meals/snacks consumed in a day, water consumption, etc.) and anthropometric measurements (body weight, height, body mass index, waist circumference, neck circumference). In the intial (pre-intervention) and final (post-intervention) stages of the study, anthropometric measurements of the participants were taken, and body composition analysis was done. In addition, biochemical findings and 3-day food consumption records were taken in the intial (pre-intervention) and final (post-intervention) stages of the study. Effects of kefir consumption on gastrointestinal system, biochemical findings, mental health, immunity and inflammation, sleep quality, was evaluated by assessment of the relevant status of participants before and after kefir intervention and comparison with the control group. 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.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
OTHER
Masking
NONE
Enrollment
65
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.
Istanbul Medipol University
Istanbul, Beykoz, Turkey (Türkiye)
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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: From enrollment to the end of treatment at 6 weeks
Physical Activity
Participants were asked to maintain their usual physical activities. The physical activity levels of the participants were evaluated with the Short Physical Activity Assessment Tool. The tool consisted of two questions focusing on 20 minutes of vigorous physical activity (running, weightlifting, cycling, etc.) and 30 minutes of moderate physical activity (mowing grass, lifting light loads, etc.). A maximum score of 8 and a minimum score of 0 could be obtained by this tool. A total score of 0-3 was considered insufficiently active, and a score of ≥4 was considered sufficiently active.
Time frame: From enrollment to the end of treatment at 6 weeks
Biochemical Parameters
Blood analysis for the following parameters (fasting blood glucose, high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), total cholesterol, triglyceride, alanine transaminase (ALT), aspartate transaminase (AST), blood urea nitrogen (BUN), urea, uric acid, creatinine, bilirubin, C-reactive protein (CRP), iron, iron binding capacity) was performed and the hemogram obtained at the beginning and end (pre and post intervention) of the study. The systemic immune-inflammation index (SII) was calculated from the hemogram findings.
Time frame: From enrollment to the end of treatment at 6 weeks
Dietary Patterns
Participants were asked to maintain their usual eating habits. They were asked to record 24-hour food consumption for three non-consecutive days, one of which was required to be a weekend. This food record was taken twice; once at the beginning (prior to kefir intervention) and the other at the end (post kefir intervention) of the study. The records were collected from the participants retrospectively. The average daily energy and nutrient intakes of the individuals were determined by taking the average of the food consumption consumption values of the three days. The dietary quality of the participants was evaluated with the HEI-2015, which was calculated using data from food consumption records. If the HEI-2015 score of the participants was ≤50 points, the diet quality was evaluated as "poor diet quality", 51-80 points as "diet quality to be improved", and \>80 points as "good diet quality".
Time frame: From enrollment to the end of treatment at 6 weeks
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