Early dietary exposure is associated with allergy development in the FARMFLORA birth cohort

Sammanfattning: The allergy prevalence is markedly low in children growing up on farms. Contact with livestock and consumption of unpasteurized milk has been associated with allergy protection, although other elements in the environment may contribute. The FARMFLORA birth cohort was established to identify factors that may be part of the allergy protection of the farming environment. In this thesis, early dietary exposures of farm and control children were evaluated in relation to allergy at three years of age, including: 1) maternal diet during pregnancy and lactation; 2) fatty acid composition of infant sera at birth and in sera and breast milk four months postpartum; 3) introduction practices of complementary foods; and 4) diet at one year of age. Twenty-eight children from dairy farms in South-Western Sweden, and 37 non-farm control children from the same rural area were included in the cohort. The children were examined clinically by pediatricians to diagnose food allergy, eczema, asthma and rhinitis.

Farming mothers consumed more full-fat dairy and saturated fats during pregnancy and lactation than control mothers, who instead consumed more margarines and oils. The same pattern was found in the children’s diet at one year of age. The higher intake of saturated fats among the farming mothers was reflected in their breast milk as higher proportions of saturated fatty acids and lower proportions of the polyunsaturated fatty acids linoleic and alpha-linolenic acid. However, the only difference found in the infants’ sera was higher proportions of arachidonic acid at birth and lower proportions of the monounsaturated omega-7 fatty acid 18:1 four months postpartum in farmers’ children. Neither did timing of introduction of complementary foods differ between farm and control children, except for an earlier introduction of nuts in farm children.

One farm child (4%) and 10 control children (25%) were allergic by the age of three years. The intake of margarines and oils both by the mothers during pregnancy and lactation and by the children at one year of age was weakly associated with allergy development at three years of age. Also, higher intakes of pork was found in subsequently allergic compared to healthy children, when farmers were excluded from the analysis. The most pronounced difference between healthy and subsequently allergic children was higher proportions of the long-chain omega-3 polyunsaturated fatty acid eicosapentaenoic acid in serum both at birth and four months postpartum, reflecting maternal fish intake during pregnancy and lactation. Concordantly, a pattern of earlier introduction of fish in the healthy children was observed, alongside higher intakes of seafood at one year of age. Healthy children also tended to introduce flour and eggs earlier. Exclusive breastfeeding was associated with less allergy, although the protective effect was only observed up to three months of age.

In conclusion, a low margarine consumption by the mother and child was weakly associated with less allergy as well as with growing up on a farm. Consumption of fish in mothers during pregnancy and lactation as well as in the early diet of children was associated with a decreased risk of allergy development, although unrelated to farm residence. Tendencies of late introduction of complementary foods were related to an increased risk of allergy development.