Some heroes are loud and legendary. Others work quietly in the background, making a difference without asking for attention. Lactobacillus rhamnosus belongs to the second group. It doesn’t come wrapped in folklore like Lactobacillus bulgaricus, the classic yoghurt bacterium, nor did it enjoy the early fame of Lactobacillus acidophilus. And yet, this modest little microbe has become one of the most researched probiotics in history — and a trusted name in gut health.

Among the many beneficial microbes that call our bodies home, Limosilactobacillus reuteri (formerly Lactobacillus reuteri) stands out for its remarkable journey from nature to laboratories to health-conscious consumers worldwide. This small bacterium, quietly performing its symbiotic duties for millennia...