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.

Lactobacillus acidophilus (L. acidophilus) is one of the best-known and most widely used probiotic bacteria, valued for its ability to support digestive, immune, and vaginal health. Found in humans, animals, and fermented foods worldwide, this “acid-loving” bacterium has a fascinating story and continues to play a crucial role in our well-being.

The idea of consuming live microbes to promote health is not new. Back in 1907, Élie Metchnikoff, a disciple of Louis Pasteur, the Father...