Testing the Immunomodulatory Effects of Probiotic Bacillus coagulans SNZ 1969® in Healthy Adults: A Randomized,...

The immune system and the gastrointestinal tract are intricately linked. The intestinal barrier, microbiome, and immune system are in constant communication, shaping immune responses and maintaining homeostasis. Imbalances in the gut microbiome can affect the intestinal barrier and increase susceptibility to infections, along with a decline in immune function (both innate and adaptive immunity). Maintaining optimal immune function is crucial for protecting against infections and supporting overall health, particularly in populations that may be more vulnerable to seasonal respiratory and gastrointestinal infections. Probiotics, particularly spore-forming strains, demonstrate potential for improving natural killer (NK) cell function and mucosal immunity through gut-associated lymphoid tissue interactions. This study evaluated the immunomodulatory effects of Bacillus coagulans SNZ 1969^® in adults.

This randomized, double-blind, placebo-controlled clinical trial enrolled adults aged 60-65 years who were susceptible to seasonal infections. Participants were randomized 1:1 to receive either B. coagulans SNZ 1969^® (2 billion CFU/day) or placebo for 12 weeks. Primary endpoints included NK cell activity, absolute NK cell count (CD3⁻/CD16⁺/CD56⁺), and immunoglobulin levels (serum IgM, IgG, and IgA and salivary IgA). Secondary outcomes assessed respiratory and gastrointestinal infection incidence, inflammatory markers (C-reactive protein), and safety parameters.

Of 60 enrolled participants, 50 completed the study (25 per group). B. coagulans SNZ 1969^® significantly enhanced NK cell activity compared to placebo, with a net increase of 42.07% between groups (44.59% versus 2.52% increase from baseline; p = 0.0002). NK cell activity improvements were consistent across both genders in exploratory subgroup analyses (limited by small female n = 7-8 per arm; males: 36.75% versus 2.52%; p = 0.00004; females: 63.64% versus 2.71%; p = 0.01155). Significant improvements were observed in serum IgA (25.00% versus 2.30% change; p = 0.0016) and salivary IgA (27.70% versus 0.60% change; p = 0.0002). No significant changes occurred in absolute NK cell counts, serum IgM, IgG, or C-reactive protein levels. Secondary analyses showed numerical reduction trends in upper respiratory tract infections (20% versus 32%; p = 0.11), gastrointestinal infections (8% versus 28%), and total illness days (23 days versus 35 days), favoring the probiotic group, though statistical significance was not achieved. The probiotic was well-tolerated with no serious adverse events.

B. coagulans SNZ 1969^® supplementation significantly enhanced NK cell activity and mucosal IgA production in adults, suggesting its potential role in strengthening the innate immune defense mechanisms. These findings support the role of B. coagulans SNZ 1969^® as a safe dietary supplement for augmenting innate cellular immune function and thereby potentially contributing to a reduced trend to infection susceptibility; however, these preliminary findings require more extensive investigation in a larger study population.