Lactobacillus rhamnosus is a probiotic bacterium commonly used to support gastrointestinal health, including the small intestine. There is moderate scientific evidence suggesting its benefits for the small intestine, particularly in the prevention and management of certain gastrointestinal disorders. Clinical studies have shown that L. rhamnosus, especially the GG strain (L. rhamnosus GG), can help restore and maintain the balance of intestinal microbiota, inhibit the growth of pathogenic bacteria, and enhance the intestinal barrier function.

Randomized controlled trials have demonstrated that L. rhamnosus supplementation may reduce the duration and severity of acute infectious diarrhea, including that caused by rotavirus, and may help prevent antibiotic-associated diarrhea. There is also evidence indicating that it can modulate immune responses in the gut, which is particularly relevant for the small intestine, a major site of immune activity. Some studies have explored its role in preventing or managing small intestinal bacterial overgrowth (SIBO) and conditions such as irritable bowel syndrome (IBS), though results are mixed and further research is needed.

In summary, while L. rhamnosus is not universally effective for all small intestine-related conditions, its use is supported by a moderate body of scientific literature for specific gastrointestinal health outcomes related to the small intestine.