Spore-forming probiotics (Bacillus subtilis, B. coagulans, B. clausii) are delivered as endospores.
The one human study that sampled the small intestine directly recovered viable spores and germinated vegetative cells from ileal effluent within 3 hours of a single capsule, with spores present in every participant by 5 hours, which supports the acid-resistance argument at the mechanistic level.
The headline numbers usually quoted for this category, a 42% lower post-meal endotoxin and a 24% lower post-meal triglyceride, come from one 30-day trial of a five-strain blend at 4 billion spores/day in adults pre-screened to have a large post-meal endotoxin spike, funded in part by the probiotic's maker.
Doses tested in the findings below run from 1 billion CFU/day (B. subtilis DE111) through 2 billion CFU/day (B. coagulans MTCC 5856) to 4 billion spores/day (five-strain blend).
Effects are strain-specific and outcome-specific, and three of the ten findings below are null.