Many societies traditionally use fermentation as a means of producing beverages, whose microbial transformation is spontaneously triggered or facilitated by the addition of a catalyst (yeasts, bacteria). Kefir is a traditional beverage belonging to the latter category.
It is a probiotic that is supposed to modify the intestinal microbiota and the metabolites produced.
Links between kefir and metabolic syndromes (insulin resistance, etc.) have also been described in animal models. Very few clinical studies have evaluated the effects of kefir in humans.
A 'positive feeling' has also been described by people who consume kefir. Kefir could therefore have an effect on people's well-being.