Study design
A multicenter, cross-sectional, observational study was performed, in which exclusively formula-fed infants were studied in four different groups based on their existing use of infant formula (IF A (FrieslandCampina, Amersfoort, The Netherlands), IF B, IF C, and IF D). The four different IFs were selected based on differences in composition and processing, the latter as illustrated by different blocked-lysine levels (shown in Additional Table This study was approved by the Ethical Committee of Hospital SMIQ S de R.L. de C.V. (CONBIOÉTICA-22-CEI-003-20171130, #16CI22014059) and by the Ethical Committee of Sociedad de Beneficencia Española, l.A.P. (CONBIOÉTICA-09-CEI-009-20170421, #15CI09016029) and was performed in accordance with the Declaration of Helsinki and its later amendments [