Timing of complementary food introduction is not associated with inflammatory bowel disease risk: A prospective birth cohort study

Abstract Background Complementary feeding (ie, food introduction besides formula or breast milk) imprints on the developing gut microbiome and immune system, which may have durable influences on disease risk. This study aimed to prospectively assess the association between the timing of complementary feeding and subsequent inflammatory bowel disease (IBD) risk. Methods We followed 94 238 participants from the All Babies in Southeast Sweden (ABIS) (n = 11 947) and the Norwegian Mother, Father and Child (MoBa) (n = 82 291) cohorts from birth (1997-2009) through 2023 (mean age 16.5 [MoBa] to 25.2 [ABIS] years). National patient registers identified IBD diagnoses. The timing of complementary food introduction ( Results Over 1 562 350 person-years of follow-up, 400 participants developed IBD (ABIS, n = 124; MoBa, n = 276). Overall timing of complementary food introduction was not associated with IBD ( Conclusions The findings from this binational birth cohort study indicate that neither the timing nor the pattern of complementary food introduction is a major risk factor for later development of IBD.