A review of five randomised controlled trials from 2005 to 2017 with 544 healthy infants (one day to 12 months of age) showed that D-lactic acid producing probiotic bacteria and fermented infant formulas did not cause D-lactic acidosis in healthy children. The only reported cases of paediatric D-lactic acidosis were in children with short bowel syndrome or, historically, in infants fed with acidified formulas.
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Reference: Łukasik J et al. Rapid review shows that probiotics and fermented infant formulas do not cause d-lactic acidosis in healthy children. Acta Paediatr. 2018. doi: 10.1111/apa.14338.