Can fish oil in pregnancy and lactation alter maternal and infant immunological responses and prevent allergy in the offspring?

Background: A connection has been proposed between the increase of allergic disease and the altered composition of fatty acids in the diet in the westernised world. Less oily fish and more vegetable oil are consumed today compared to 50-100 years ago. Programming of the immune responses takes place very early in life and environmental factors, such as fish in the diet, have been suggested to protect from infant allergy. Aim: The general aim of this thesis was to assess the effects of maternal dietary supplementation with ω-3 long chain polyunsaturated fatty acids (LCPUFA), i.e. fish oil, in pregnancy and lactation on the development of allergic symptoms and sensitisation in the infants as well as some immunological markers in mothers and infants. Subjects and methods: This thesis is based on the results from a prospective double-blind placebo-controlled multi-centre trial comprising 145 families. Pregnant women, at risk of having an allergic infant, were recruited at the antenatal clinics and randomised to daily supplementation with 1.6 g eicosapentaenoic acid (EPA, C20:5ω-3) and 1.1 g docosahexaenoic acid (DHA, C22:6ω-3) or placebo, starting in the 25th gestational week and continuing through 3.5 months of breastfeeding. Phospholipid fatty acids in maternal and infant plasma were analysed to assess compliance. Maternal prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and cytokines along with infant vaccine induced responses and chemokines were analysed with ELISA and Luminex techniques. Clinical outcomes were allergic disease and positive skin prick test/detectable circulating IgE antibodies to common allergens. Results: Phospholipid proportions of ω-3 LCPUFA increased significantly in the ω-3 supplemented women and their infants. Lipopolysaccharide-induced PGE2 secretion from whole blood culture supernatants decreased in a majority of the ω-3-supplemented mothers (p<0.01). The decrease in PGE2 production was more pronounced among non-atopic than atopic mothers. No difference in the prevalence of allergic symptoms was found between the intervention groups. The cumulative incidence of IgE associated eczema and IgE mediated food allergy was though reduced in the ω-3 group during the first two years (OR=0.2 and 0.3 compared to placebo, p<0.05 for both). The cumulative incidence of any IgE associated disease during the first two years of life was 13% in the ω-3 supplemented group compared to 30% in the placebo group (p=0.01, OR 0.3, p<0.05). This effec