Lactobacillus helveticus GCL1815 induces salivary IgA production and alleviates common cold-like symptoms: A randomized, double-blind, placebo-controlled, parallel-group comparative study

Lactobacillus helveticus GCL1815 has been shown to suppress cold-like subjective symptoms and activate dendritic cells in prior clinical studies. This randomized, double-blind, placebo-controlled, parallel-group study was conducted to determine the effects of low or high doses of GCL1815 on physical condition and immune indices. In this study, a low-dose group of 6 × 10 9 GCL1815 cells/day and a high-dose group of 1 × 10 11 GCL1815 cells/day were compared to a placebo group. A cold-like symptom questionnaire was established as the primary endpoint of the study. Both the low-dose and high-dose groups showed significant improvement in several systemic and local cold-like symptoms after 8 weeks of GCL1815 intake. This intervention was also found to enhance salivary sIgA secretion rate. No safety concerns were observed even in the high-dose group. These results suggest continuous intake of heat-sterilized GCL1815 for 8 weeks promoted sIgA secretion and reduced systemic and local cold-like symptoms. • Lactobacillus helveticus GCL1815 showed significant improvement in several systemic and local cold-like symptoms in healthy adults. • Both low and high dose groups showed comparable efficacy in symptom improvement. • Continuous intake of GCL1815 enhanced salivary sIgA secretion rate. • High-dose group demonstrated favorable safety profiles with no serious adverse events.