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

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.