Decreased duration of acute upper respiratory tract infections with daily intake of fermented milk: A multicenter, double-blinded, randomized comparative study in users of day care facilities for the elderly population

Background There is insufficient evidence of preventive effect of probiotics on upper respiratory tract infections (URTIs) in an elderly population. Methods We conducted a multicenter, double-blinded, randomized, placebo-controlled parallel group study. Elderly persons had participated who used day care at 4 facilities in Tokyo. We used fermented milks containing Lactobacillus casei strain Shirota (LcS) and placebo drinks as test drinks. Results A total of 154 subjects was analyzed. The number of persons diagnosed with an acute URTIs was almost identical in both groups (LcS: 31, placebo: 32), whereas the number of acute URTIs events (LcS: 68, placebo: 51) and the symptom score (LcS: 425, placebo: 396) were both higher in the LcS group. Permutation tests performed using the total number of acute URTIs infection events/total days of observation and the total symptom score/total days of observation found no statistically significant difference respectively (P values of.89 and.64, respectively). Comparing the mean duration of infection per infection event found a shorter mean duration in the LcS group (LcS: 3.71 days, placebo: 5.40 days), and the difference was statistically significant. Conclusion The results suggest that fermented milk containing LcS probably reduces the duration of acute URTIs.