Bioactive Compounds from Kefir and Their Potential Benefits on Health: A Systematic Review and Meta‐Analysis

Abstract

Despite evidence of health benefits from kefir administration, a systematic review with meta-analysis on bioactive compounds associated with these benefits is still absent in the literature. Kefir is fermented milk resulting from the metabolism of a complex microbiota in symbiosis. Recent researches have investigated the bioactive compounds responsible for the preventive and therapeutic effects attributed to kefir. However, differences in functional potential between industrial and artisanal kefir are still controversial. Firstly, we identified differences in the microbial composition among both types of kefir. Available evidence concerning the action of different bioactive compounds from kefir on health, both from in vitro and in vivo studies, was subsequently summarized to draw a primary conclusion of the dose and the intervention time for effect, the producer microorganisms, the precursor in the milk, and the action mechanism. Meta-analysis was performed to investigate the statistically significant differences ( P < 0.05 ) between intervention and control and between both types of kefir for each health effect studied. In summary, the bioactive compounds more commonly reported were exopolysaccharides, including kefiran, bioactive peptides, and organic acids, especially lactic acid. Kefir bioactive compounds presented antimicrobial, anticancer, and immune-modulatory activities corroborated by the meta-analysis. However, clinical evidence is urgently needed to strengthen the practical applicability of these bioactive compounds. The mechanisms of their action were diverse, indicating that they can act by different signaling pathways. Still, industrial and artisanal kefir may differ regarding functional potential—OR of 8.56 (95% CI: 2.27–32.21, P ≤ .001 )—according to the observed health effect, which can be associated with differences in the microbial composition between both types of kefir.

Pequi (Caryocar brasiliense) Waste Extract as a Synergistic Agent in the Microbial and Physicochemical Preservation of Low-Sodium Raw Goat Cheese

“…It can induce a decrease in a * values because the whey released by the gel contains riboflavin, which has a very important green component ( 56 ). A decrease in a * values with storage and its positive correlation with pH was previously reported for goat’s fermented milk ( 62 ) and also for goat’s cheese added with essential oil ( 63 ).…”

Changes in hepatic thiol contents and regulation of glutathione S-transferase by high-fructose diet: Effects of kefir and some probiotic bacteria

“…Kefir, one of the well-known probiotics has been shown to exert anti-inflammatory, antiviral, and anti-allergic effects [39]. Its protective activities have also been established against metabolic diseases caused by fructose [19].…”

Metagenomic and Functional Characterization of Two Chilean Kefir Beverages Reveals a Dairy Beverage Containing Active Enzymes, Short-Chain Fatty Acids, Microbial β-Amyloids, and Bio-Film Inhibitors

“…According to metagenomic analyses, ethanol produced by yeast can be metabolized by Alphaproteobacteria to produce acetic acid by oxidation of ethanol [ 92 ]. In kefir, SCFA contribute to its organoleptic and preservative properties [ 93 , 94 ]. Besides its relevance for carbon and energy metabolism of the microbial ecosystem of kefir, glucose, and galactose produced by Firmicutes can be used as substrates for the biosynthesis of kefiran, the main polysaccharide of the extracellular matrix of kefir, which is essential for the formation of the macroscopic structure of kefir grain and its propagation [ 87 ].…”