One hundred-eighteen infants (mean age, 7 months) were randomly assigned to receive, in double-blind fashion, either 1) a standard milk-based formula containing 1 x 107 colony-forming units (CFU)/g each of Bifidobacterium lactis and Streptococcus thermophilus, 2) a formula containing 1 x 106 CFU/g each of B. lactis and S. thermophilus, or 3) unsupplemented formula for a mean of 210 days. Compared with the unsupplemented formula, each of the supplemented formulas was associated with a lower frequency of reported colic or irritability (p < 0.001) and a lower frequency of antibiotic use (p < 0.001). No significant adverse effects were seen.

Comment: The results of this study demonstrate that long-term consumption of infant formulas supplemented with B. lactis and S. thermophilus reduced the incidence of colic and irritability, and resulted in a lower need for antibiotics. Other studies have shown that feeding probiotic organisms to infants or young children can reduce the incidence of infections and decrease the incidence or severity of eczema. Probiotics probably work by encouraging the growth of “friendly” intestinal flora, and possibly by promoting the development of a healthy immune system.

Saavedra JM, et al. Long-term consumption of infant formulas containing live probiotic bacteria: tolerance and safety. Am J Clin Nutr 2004;79:261-267.