L. acidophilus exists naturally in the body, mostly found in the upper gastrointestinal tract known to be a "friendly bacteria", L. acidophilus helps maintain healthy intestinal flora, leading to better overall digestion and immune function by cultivation an environment that staves off bad bacteria. With a proprietary blend of 13 probiotic strains that are live at the time of manufacture-including lactobacillus acidophilus colony forming units-Zahler's Biodophilus helps support better digestion. Biodophilus also helps recolonize the intestines with healthy bacteria, improving the body's immune function, particularly after antibiotic use, as antibiotic kill off all bacteria indiscriminately.