Lactobacillus kefiri is a probiotic strain commonly found in kefir, a fermented milk beverage. The use of probiotics, especially lactic acid bacteria, for lactose intolerance is primarily supported by scientific rationale rather than traditional use specifically for this condition. The scientific evidence supporting L. kefiri stems from its ability to produce the enzyme β-galactosidase (lactase), which helps break down lactose in the gut, potentially aiding individuals with lactose intolerance.

Several studies on kefir as a whole have demonstrated that consuming kefir can improve lactose digestion and reduce symptoms of lactose intolerance in humans. This effect is attributed to the combined action of kefir’s microbial community, including L. kefiri, which can predigest lactose during fermentation and continue to assist lactose hydrolysis in the digestive tract. Some in vitro and animal studies have specifically shown that L. kefiri can survive gastric transit and express lactase activity, theoretically supporting its use for lactose digestion.

However, direct clinical evidence on L. kefiri as a single strain (apart from the whole kefir matrix) for lactose intolerance in humans is limited. Most studies evaluate kefir as a complex food rather than isolated L. kefiri. Therefore, while there is a plausible scientific mechanism and some supportive data, the strength of evidence is modest, justifying a rating of 2 out of 5.