Fermented formulas, i.e., those fermented with lactic acid-producing bacteria during the production process and not containing significant amounts of viable bacteria in the final product, are widely available in many countries. Our aim was to systematically review published evidence related to the safety and health effects of the administration of fermented infant formulas compared with standard infant formulas. The Cochrane Library, MEDLINE, and EMBASE databases and major pediatric conference proceedings were searched. Five randomized controlled trials (RCTs) involving 1326 infants met the inclusion criteria. Compared with standard formula, the use of fermented formula resulted in a similar weight gain and length gain during the study period. Data from one RCT, albeit large, suggest the effectiveness of fermented formula in preventing and treating acute diarrhea. Fermented formula has the potential to reduce some, albeit not well-defined, digestive symptoms. Current evidence does not support the use of fermented formula for preventing cow's milk allergy.
Conclusion: Limited available evidence suggests that the use of fermented infant formula, compared with the use of standard infant formula, does not offer clear additional benefits, although some benefit on gastrointestinal symptoms cannot be excluded. What is known • Fermented formulas, i.e., those fermented with lactic acid-producing bacteria during the production process and not containing significant amounts of viable bacteria in the final product, are widely available in many countries. What is new • Limited evidence available suggests that the use of fermented infant formula, compared with the use of standard infant formula, does not offer clear additional benefits, although some benefit on gastrointestinal symptoms cannot be excluded. At the same time, no negative health effects have been documented.
Keywords: Children; Feeding; Fermented formula; Nutrition; RCT.