Lactobacillus kefiri is a probiotic bacterium commonly found in kefir, a fermented milk product. Its use to support the small intestine is scientifically supported to a moderate degree. Several studies have demonstrated that L. kefiri can modulate the gut microbiota and exhibit antagonistic activity against certain gastrointestinal pathogens. Research shows that strains of L. kefiri can adhere to intestinal epithelial cells, potentially enhancing the gut barrier and promoting immune modulation within the small intestine.

In vitro and animal studies have found that L. kefiri can reduce inflammation, inhibit pathogen adhesion, and produce antimicrobial substances that may help maintain a healthy gut environment. For example, a 2016 study (Carasi et al., Frontiers in Microbiology) showed that L. kefiri administration in mice helped regulate cytokine production and improved mucosal immune responses in the gut.

However, direct clinical evidence in humans, specifically targeting small intestine function, is still limited. Most human studies involve mixed-strain probiotics or focus on overall gut health rather than just the small intestine. Nevertheless, the available data suggest that L. kefiri may provide benefits for gut microbial balance and immune support, which are relevant to small intestine health.

In summary, while mechanistic and preclinical evidence is promising, more targeted human trials are needed for a higher evidence rating.