There is considerable interest in the role of probiotics in immune function. The objective of this systematic review and meta-analysis was to assess the effects of the consumption of a fermented dairy drink containing Lacticaseibacillus paracasei subsp. paracasei CNCM I-1518 (the previous taxonomic nomenclature was Lactobacillus casei CNCM I-1518, prior to the nomenclature change in April 2020) and the standard yogurt cultures (hereinafter referred to collectively as "FDD") on common infectious diseases (CIDs) in generally healthy children and adults. Nine literature databases were searched, and nine randomized controlled trials from eight publications were eligible for inclusion. Combined effect sizes were determined for three metrics of CID incidence, two metrics of CID duration, and one metric of CID severity. Compared to the control, the consumption of the FDD resulted in (1) a significant reduction in the odds of experiencing ≥1 CID (odds ratio (OR) (with a 95% confidence interval (CI)): 0.81 (0.66, 0.98); p = 0.029); (2) a significant reduction in mean CIDs per subject (-0.09 (-0.15, -0.04); p = 0.001); and (3) a trend towards reduced risk in cumulative CIDs (relative risk (RR): 0.91 (0.82, 1.01); p = 0.082). The consumption of the FDD had no significant effect on CID duration or severity. Based on the studies conducted thus far, these results suggest that the FDD may reduce CID incidence in the general population.
Keywords: Lacticaseibacillus paracasei subsp. paracasei CNCM I-1518; Lactobacillus casei CNCM I-1518; Lactobacillus casei DN-114 001; common infectious disease; fermented dairy; fermented milk; gastrointestinal infection; immune function; probiotic; respiratory infection.