Bacillus Subtilis for Immune Function

Research suggests that Bacillus subtilis may support immune function across a range of animal models, with studies consistently reporting improvements in immune cell activity, antibody production, and inflammatory signaling markers. The available evidence comes primarily from animal studies — including trials in broiler chickens, piglets, dairy calves, mice, and fish — with two small randomized controlled trials contributing to the base; no human clinical trials were identified among the reviewed literature. Studies indicate that B. subtilis supplementation is broadly associated with enhanced innate and adaptive immune responses, including increased natural killer cell activity, higher IgG and IgM levels, improved gut barrier integrity, and favorable shifts in immune signaling molecules such as IFN-γ and IL-6, though one poultry study reported mixed results depending on growth phase and concurrent antibiotic use. The near-exclusive reliance on animal research is a meaningful limitation, and while findings are directionally consistent, it remains unclear how well these effects translate to human immune function.