In a randomized controlled trial, the probiotic Bifidobacterium animalis subsp. lactis—used in many probiotic products, including Dannon’s Activia yogurts—did nothing to improve bowel health in people with constipation, according to data from a randomized triple-blind placebo-controlled clinical trial Wednesday in JAMA Network Open.
Stomach acid doesn’t kill all bacteria or pathogens. That’s how I got whipworm, roundworm, E. coli and giardia from food in India. Some bacteria may be more or less susceptible to the stomach environment. It looks like tests have shown some probiotics do tend to survive the stomach.