The Effects of Kefir and Kefir Components on Immune and Metabolic Physiology in Pre-Clinical Studies: A Narrative Review

Abstract

Kefir, a fermented beverage made from kefir grains, has gained immense popularity around the world due to its potential health-promoting properties. Kefir beverages are both marketed commercially and brewed privately by individuals. Both milk and sugar solutions can be used as substrates with various additives included based on consumer preference. Fermentation occurs via microorganisms including lactic acid bacteria, acetic acid bacteria, and yeasts, which are naturally present in kefir grains. Health-promoting effects of kefir are thought to occur through immune, gastrointestinal, and metabolic regulation. Both clinical trials and mechanistic studies in cell culture and animal models have explored these effects. Studies in vitro and in animals have shown the ability of kefir and kefir components to antagonize pathogens, reduce proinflammatory cytokine production, contribute to cytotoxicity of tumor cell lines and reduce tumor burden, and improve serum glycemic and lipid profiles. However, some data from clinical trials are conflicting, and the precise mechanisms by which kefir promotes well-being are not completely defined. This review summarizes the current body of evidence in both cell culture and animal models that provide insight into the mechanisms by which kefir beverages may protect consumers from enteric infections and improve immune and metabolic health. We believe that readers will gain knowledge helpful for both developing more targeted mechanistic studies and selecting informative outcomes when designing clinical studies.

A Clinical Outcome of the Anti-PD-1 Therapy of Melanoma in Polish Patients Is Mediated by Population-Specific Gut Microbiome Composition

“…Moreover, several studies presented the association between dairy product consumption and favorable changes in the gut microbiota composition, and these changes correlated with a reduced risk of cardiovascular disease development in mice and humans [ 80 , 81 , 82 ]. In addition, dairy products were found to affect immune and metabolic pathways [ 83 ]. A growing body of evidence presenting the association between dairy product consumption and gut microbiota composition and immunity, alongside the results found in the present study, suggest that the response to anti-PD-1 therapy may be affected by dairy product consumption.…”

A Clinical Outcome of the anti-PD-1 Therapy of Melanoma in Polish Patients Is Mediated by Population-Specific Gut Microbiome Composition

“…Moreover, several studies presented the association between dairy product consumption and favorable changes in the gut microbiota composition, and these changes correlated with reduced risk of cardiovascular disease development in mice and humans [107][108][109]. In addition, dairy products were found to affect immune and metabolic pathways [110]. A growing body of evidence presenting the association between dairy product consumption and gut microbiota composition and immunity, alongside results found in the present study our data suggests that response to the anti-PD-1 therapy may be affected by dairy product consumption.…”

From the past to the future: Fermented milks and their health effects against human diseases

“…Kefir has now been proven to have a wide range of health benefits, such as antimicrobial activity (Bekar et al., 2011), against viral infection (Hamida et al., 2021), antihypertensive (Friques et al., 2015), immune regulation, antioxidant effect, anti‐diabetes effect (Bellikci‐Koyu et al., 2022; Nurliyani et al., 2015), anti‐allergic effect, and anti‐tumor (Azizi et al., 2021; Slattery et al., 2019). The anti‐carcinogenic role of kefir and the fractions of kefir can be related to the prevention of cancer and retardation of tumor growth by apoptosis (Maalouf et al., 2011), immune response (Culpepper, 2022), modulation of gut microbiota (Peluzio et al., 2021; Yılmaz et al., 2019), decreased tumor growth and DNA damage (Zeng et al., 2021), anti‐oxidative process (Ali et al., 2020; Kumar et al., 2021), and inhibition of proliferation, and activation of pro‐carcinogens (Rafie et al., 2015; Sharifi et al., 2017). The main components of kefir are lactic acid, ethanol, and CO 2 , in addition to bioactive components, including peptides, EPS, and sphingolipids, which play important roles in different signaling pathways and confer kefir a variety of health benefits (Farag et al., 2020).…”