Lactobacillus kefiri is a species of lactic acid bacteria commonly isolated from kefir, a fermented milk beverage. Its use for Irritable Bowel Syndrome (IBS) is primarily supported by scientific interest rather than a long-standing traditional association with treating this specific condition. While kefir and its component microbes have been consumed traditionally for general gut health, direct, high-quality evidence for L. kefiri in IBS is limited.

Some pilot clinical studies and preclinical research suggest that L. kefiri may have beneficial effects on gut microbiota composition, intestinal barrier function, and inflammation, all of which are factors implicated in IBS. For example, a small randomized clinical trial (Lorea Barros et al., 2017) found that a multi-strain kefir containing L. kefiri improved some IBS symptoms compared to placebo. However, the evidence is mostly preliminary, with small sample sizes, lack of strain specificity, and variability in study designs. Systematic reviews on probiotics in IBS occasionally mention kefir or L. kefiri but emphasize the need for larger, well-controlled studies.

In summary, while there is some scientific rationale and early clinical data supporting the use of L. kefiri for IBS, the overall evidence is weak to moderate (score: 2/5). Its use is not strongly established by either tradition specifically for IBS or by robust clinical validation.