Bifidobacterium lactis is a probiotic bacterium commonly studied for its effects on gastrointestinal health, including the small intestine. There is scientific evidence supporting its role in supporting the small intestines, though the strength of evidence is moderate rather than definitive (hence a rating of 3 out of 5). Several clinical trials and reviews have shown that B. lactis can help maintain a healthy balance of gut microbiota, which is crucial for small intestinal health. For example, B. lactis supplementation has been associated with improvements in symptoms of irritable bowel syndrome (IBS), such as bloating and abdominal discomfort, and may enhance the intestinal barrier function, reduce gut permeability, and modulate immune responses in the gut.

Specifically, B. lactis has been shown to increase populations of beneficial bacteria and decrease the presence of potential pathogens in the small intestine. Some studies also suggest that it supports digestion (including lactose digestion) and reduces inflammation, both of which are relevant to small intestinal health. However, much of the evidence comes from studies on probiotic blends rather than B. lactis alone, and there is variability in results depending on the population and study design. Therefore, while the scientific rationale for B. lactis supporting the small intestine is solid, more high-quality, strain-specific research is needed to fully confirm its benefits.