Lactobacillus crispatus is a species of lactic acid bacteria that is a natural part of the human microbiota, most notably in the vaginal and, to a lesser extent, the gastrointestinal tract. Scientific evidence supports its beneficial role in maintaining a healthy microbial balance in the colon (large intestine), although much of the research focuses on its impact on the vaginal environment. In the context of the large intestine, several studies have identified L. crispatus among the Lactobacillus species that can help inhibit the growth of pathogens through the production of lactic acid and bacteriocins, which lower the intestinal pH and create an environment less hospitable to harmful bacteria.

Clinical research demonstrates that certain strains of L. crispatus can survive gastrointestinal transit and transiently colonize the colon, where they may support the mucosal barrier and modulate the immune response. There is also evidence that Lactobacillus species, including L. crispatus, can contribute to the maintenance of intestinal health and may reduce the risk of diarrhea associated with antibiotics or infections by restoring beneficial flora after disturbances. However, the majority of probiotic research for colon health centers on other species such as L. rhamnosus and L. plantarum, and more targeted clinical studies on L. crispatus for colon-specific outcomes are warranted. The current evidence base nonetheless justifies its use as a supportive probiotic for large intestine health.