Lactobacillus (mixed strains) has been investigated for its potential role in supporting intestinal barrier function, which is central to the concept of "Leaky Gut Syndrome" (increased intestinal permeability). Several preclinical studies, including in vitro and animal models, suggest that certain Lactobacillus strains can enhance tight junction integrity, reduce inflammation, and modulate gut microbiota composition—all mechanisms that may help maintain or restore the gut barrier. A few small human studies have reported improvements in intestinal permeability markers following supplementation with mixed probiotics, including Lactobacillus species, particularly in populations with specific gastrointestinal disorders (e.g., irritable bowel syndrome, inflammatory bowel disease).

However, "Leaky Gut Syndrome" as a standalone diagnosis is not widely recognized in mainstream medicine, and robust clinical trials directly studying Lactobacillus supplementation in individuals diagnosed specifically with "Leaky Gut Syndrome" are lacking. Most available evidence comes from studies on related conditions, and results are sometimes inconsistent due to differences in probiotic strains, dosages, and study designs. Systematic reviews and meta-analyses highlight the need for more rigorous research but acknowledge that probiotics, including Lactobacillus, may offer some benefit for gut barrier health. In summary, there is preliminary scientific support for the use of Lactobacillus in improving gut barrier function, but direct evidence for its efficacy in treating "Leaky Gut Syndrome" in humans remains limited.