Effects of Consumption of a Fermented Dairy Product Containing the Probiotic Lactobacillus casei DN-114 001 on Common Respiratory and Gastrointestinal Infections in Shift Workers in a Randomized Controlled Trial

Abstract

Objective: The risk of infection may be increased in people under stress such as shift workers. This study examined the effect of a fermented dairy product containing the probiotic Lactobacillus casei DN-114 001 (verum) on the incidence of respiratory and gastrointestinal common infectious diseases (CIDs) and on immune functions in healthy shift workers.Methods: The study was single-center, randomized, double-blind, and controlled. Volunteers received 200 g/day of verum (n = 500) or control product (n = 500) for 3 months; 1-month follow-up was carried out.Results: The cumulated number of CIDs (primary outcome) was not significantly different between groups. Because the Poisson distribution of the primary parameter did not fully fit the observed data, a post hoc categorical analysis was applied and showed a significantly lower cumulated number of CIDs in the verum group during the product consumption phase (odds ratio [OR] = 0.75, 95% confidence interval [CI] 0.59–0.95, p = 0.017). Verum also reduced the proportion of volunteers experiencing at least 1 CID (43% vs. 51%, p = 0.005), increased the time to the first occurrence of CID (p = 0.017) in the whole population, and reduced the cumulated number of CIDs in the subgroup of smokers (p = 0.033). In the course of CID, cumulated duration of fever was lower in the verum group (in the whole study phase) (p = 0.022), and an increase in leukocyte, neutrophil, and natural killer (NK) cell counts and activity (p = 0.047 to p < 0.001) was observed compared with control group. Verum was safe and well tolerated.Conclusion: The results indicate that daily consumption of a fermented dairy product containing Lactobacillus casei DN-114 001 could reduce the risk of common infections in stressed individuals such as shift workers.