To determine whether long-term daily consumption of milk containing probiotic Lactobacillus rhamnosus GG (GG) decreases respiratory illness in children. A randomized, double-blind, placebo-controlled trial was conducted with 523 children aged 2-6 years attending day care centers in Finland. Subjects received either normal milk or the same milk with GG on three daily meals for 28 weeks. Daily recording of children' symptoms was done by parents. Primary outcome data from 501 subjects were available for analysis, and data from 128 subjects were analyzed as completed cases in terms of recovery of GG in fecal samples. Number of days with at least one respiratory symptom in all subjects was 5.03/month (95% confidence interval (CI): 4.92-5.15) in the GG group and 5.17/month (95% CI: 5.05-5.29) in the placebo group incidence rate ratio (IRR) 0.97; 95% CI: 0.94-1.00; P=0.098). In the completed cases, the figures were 4.71 days/month (95% CI: 4.52-4.90) in the GG group and 5.67 days/month (95% CI: 5.40-5.94) in the placebo group (IRR 0.83; 95% CI: 0.78-0.88; P<0.001). Consumption of GG reduced the occurrence of respiratory illness in children attending day care centers in the completed cases subgroup, but not in the total population. Thus, future clinical trials are warranted to clarify the association between fecal recovery of a probiotic and the symptom prevalence.
