Age and feeding method dependence of gamma‐glutamyltransferase levels in non‐jaundiced newborns

To compare gamma-glutamyltransferase (GGT) levels in non-jaundiced breast and formula-fed newborns as a function of age, we retrospectively studied the laboratory findings of all infants without jaundice, infection, or known liver dysfunction, who underwent liver function tests, including GGT levels, in the emergency departments of the two university hospitals in Marseille, France, between January 2022 and October 2023. GGT levels were higher in breastfed newborns (mean ± standard deviation, 101 ± 74 IU/L) than in mixed-fed (77 ± 93 IU/L) or formula-fed newborns (64 ± 54 IU/L), and were significantly and independently associated with age (p < 0.001) and feeding method (p = 0.018 for formula-fed vs. breastfed children; β, p = 0.18 for mixed-fed vs. breastfed children). GGT levels were not associated with sex, gestational age at birth, or birth weight. Clinicians should bear these relationships in mind when investigating high liver enzymes in breastfed newborns.