Probiotics

Probiotics are live microorganisms taken to influence the gut microbial community, and the useful truth about them is that "probiotic" is a category rather than a single ingredient — different strains have been studied for very different outcomes, and results with one strain rarely transfer to another. Lactobacillus rhamnosus GG has some of the strongest evidence for antibiotic-associated diarrhoea; Saccharomyces boulardii, the one yeast in wide use, has separate evidence for the same use and for traveller's diarrhoea; spore-forming Bacillus strains survive stomach acid without refrigeration, which is a formulation advantage rather than an efficacy claim on its own. Colony-forming units (CFU) are the label metric, but a high CFU count from strains without matching human trials is a weaker product than a lower count of a well-studied strain. Most benefits fade within a couple of weeks of stopping, so probiotics behave more like a running intervention than a one-time reset.

Stack Almanac tracks which probiotic strain and CFU count you're taking, so a broad-spectrum blend and a specific-strain formula bought for different reasons don't get treated as interchangeable.