Kefir: The Better Probiotic than Yogurt

Kefir is a yogurt-like food that originated in the Caucasus Mountains of Eastern Europe and Western Asia. The Caucasus mountains are situated between the Black Sea and the Caspian Sea. Like yogurt, kefir is a natural complex probiotic. Probiotic is a term that refers to foods that contain and promote the growth of beneficial bacteria within the gastrointestinal system. Kefir has been shown to contain more than 50 species of bacteria as well as several different strains of yeast. The beneficial bacteria in kefir includes lactic acid bacteria (numerous Lactobacillus species and Lactococcus species) and acetic acid bacteria. The beneficial yeasts in kefir include numerous Candida species and Saccharomyces species. The key distinguishing feature between kefir and yogurt is the high concentration of yeasts in kefir, when compared to yogurt.

The consumption of kefir has been touted to provide cholesterol lowering properties, anti-cancer properties, anti-diabetes properties, anti-inflammatory properties (e.g. anti-allergy, and anti-asthmatic properties), and anti-stress properties. In spite of the fact that there is increasing evidence indicating that the consumption of probiotic yeasts provide beneficial effects on ones health, the precise underlying mechanisms for their benefits remain unclear. Studies have shown that in laboratory mice the consumption of kefir does indeed lead to increased intestinal yeast populations, but up until now no clear metabolic benefit has been correlated to this effect.

However, a new study recently published in the Journal of Nutritional Biochemistry has shown that kefir consumption by laboratory mice prevents obesity and fatty infiltration of the liver (hepatic steatosis) even when fed a high-fat diet, HFD:

Kefir alleviates obesity and hepatic steatosis in high-fat diet fed mice by modulation of gut microbiota and mycobiota: targeted and untargeted community analysis with correlation of biomarkers

The work carried out in this study was designed to assess the potential efficacy of kefir consumption in the reduction of the likelihood for obesity and non-alcoholic fatty liver disease (NAFLD) in a mouse model of high-fat diet-induced obesity. In addition, the study carried out an analysis of the fecal microbiota (bacterial and yeast composition of the gut). The mice were orally administrated either kefir or milk (control) once a day for 12 weeks followed by analysis of a variety of physiological and pathological parameters. These parameters included organ weight, fecal microbiota and mycobiota, histopathology, blood cholesterol and cytokines and gene expression profiles.

The outcomes of the study showed the kefir feeding, but not milk feeding, even within the background of a high-fat diet, resulted in a significant reduction in body weight, significant reductions in liver pathology, and increased expression of genes involved in fatty acid oxidation in both the liver and in fat (adipose) tissues. The kefir-fed mice also had much higher levels of Lactobacillus and Lactococcus strains of bacteria and total yeast including Candida in their intestines compared to the milk-fed mice. Kefir consumption was also correlated to reductions in the level of pro-inflammatory markers, such as interleukin-6 (IL-6), in the blood. Overall the results of this study demonstrate that the consumption of kefir lead to significant alterations in the gut microbiome (both bacteria and yeast) and that these changes in the microbiome were directly correlated to reductions in obesity, reduction in liver pathology normally associated with a high-fat diet, and reductions in systemic inflammation which is also normally highly correlated with a high-fat diet. One of the major molecular consequences of the consumption of kefir discovered in this study was an elevation in the pattern of expression of genes involved in metabolism of fats. These molecular changes can be directly correlated to the reduced pathology in the liver even in the presence of a high-fat diet.

The TAKE HOME from this study is that kefir is definitely a better dietary addition than yougurt that one should consider in their search for a healthy disease fighting diet. Caution needs to be taken in that just because this study demonstrated that, even in the face of a high-fat diet, the animals fed kefir had reduced pathology and overall weight, that humans should not presume that just by adding kefir to their diet they can still go out and eat a greasy hamburger and double fries and a sweetened beverage and expect to remain healthy. Kefir consumption should be considered an addition to a healthy diet and lifestyle, NOT as an excuse to overeat.

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