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

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.

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 (<4, 4-5, or ≥6 months) was assessed using early-life food diaries and questionnaires. Latent class analyses identified 4 patterns across introductions of major food groups (eg, cereals and dairy). Cox regression estimated hazard ratios (aHRs) for IBD adjusted for socio-demographics and parental IBD. Sensitivity analysis additionally adjusted for breastfeeding duration, formula feeding, and perinatal factors.

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 (<4 months: aHR, 1.04 [95% CI, 0.67-1.60]; 4-5 months: aHR, 0.83 [95% CI, 0.63-1.10] vs ≥6 months). Also, aHRs for IBD by latent class analyses-defined introduction patterns approached 1. Results were consistent across cohorts, sensitivity analyses, and Crohn's disease and ulcerative colitis subtypes.

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.