Food introduction during the first year of life in a Swedish birth cohort – associations with allergy at 6 years of age

BACKGROUND: Diet contains components that may exert broad immunoregulatory properties, including the promotion of tolerance. The timing of food introduction may influence the development of allergies. The aim of this study was to relate the timing of food introduction with doctor's diagnosed allergies (food allergy, atopic eczema, and allergic asthma) at six years of age in a cohort of Swedish infants. METHODS: At six years of age, 430 children from the Swedish NICE birth cohort were assessed for food allergies, atopic eczema, and allergic asthma by a pediatric allergologist. Timing of introduction of 18 predefined foods (potatoes and roots, fruits and/or fruit juice, berries, nuts and/or almonds, peanuts and/or peanut oil, bread and/or biscuits, butter, margarine, vegetable oils, cow's milk, ice cream, sour milk ("fil"), yoghurt, meat, fish, eggs, porridge, and gruel) was collected monthly via parent-completed web-based questionnaires. Associations were examined using logistic regression adjusted for allergic heredity. RESULTS: During the first year of life, 27% of the children received peanuts and/or peanut oil and 32% nuts and/or almonds. Earlier meat introduction was associated with 24% lower odds of food allergy per month earlier introduced [adjusted OR (95% CI): 0.76 (0.60-0.99), p = 0.028]. A similar tendency was observed for eggs, although not surviving adjustment for allergic heredity. Children with food allergies had been introduced to margarine earlier than non-allergic children [9.0 (5.0-12.0) vs. 12.0 (9.0-12.0) months, p = 0.021], although this finding likely reflects reverse causation. CONCLUSIONS: Our results suggest that earlier introduction of meat may be associated with a lower risk of food allergies later in childhood, although this finding must be interpreted with caution as causality cannot be proven. Timing of food introduction did not appear to be associated with atopic eczema or allergic asthma. Furthermore, our results indicate that recommendations for introduction of potentially allergenic foods during the first year of life were not effectively implemented. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05809479, 12 April 2023, Retrospectively registered.