A comprehensive review on kefir: composition, microbial diversities, meta-analysis and biological significances on human health

Kefir is a probiotic-rich beverage that is fermented with beneficial microorganisms that live together in symbiotic association within kefir. The most established health benefits of kefir include gut and digestive health, owing to its rich probiotic diversity, which enhances intestinal balance and lactose digestion. Kefir consumption is associated with certain health enhancing outcomes, including anti-atherosclerotic, anti-inflammatory, antihypertensive, antioxidant, antibacterial, anticancer, and antidiabetic effects. Strong outputs were obtained via antimicrobial, immunomodulatory, anti-inflammatory, and antioxidant effects, supported by extensive experimental evidence. Emerging studies suggest anticancer, antidiabetic, and neuroprotectiveepotentials, although further clinical validation is required. Using the Scopus database, 202 documents published between 2013 and 2022 were identified and submitted for bibliometric analysis using VOSviewer software. Regarding recent applications, 107 documents on kefir published between 2021 and June 2023 were identified. This systematic review provides updated insights into the evaluation of kefir, including its nutritional and microbiological compositions. It also highlights the biological activities of kefir microbiota and emphasizes the significance of kefiran as a functional component.