Salmon in Pregnancy Study (SIPS): the effects of increased oily fish consumption on maternal nutrient intake, fatty acid status and immunity

Abstract

The prevalence of childhood atopic diseases (eczema, asthma, allergies, hay-fever) has increased during the last 30 years. Epidemiological studies link higher fish intake during pregnancy with lower risk of atopy in the offspring. Oily fish provide the long chain (LC) n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as vitamin D and antioxidants (selenium). Fish oil provides EPA and DHA and fish oil supplementation during pregnancy alters offspring immunity in a way that would be consistent with lowered risk of atopy. There are no studies of oily fish intervention in pregnancy. The Salmon in Pregnancy Study (SIPS) is the first randomised controlled trial of oily fish intervention during pregnancy. The main outcome measures of SIPS were the clinical signs of atopy in the offspring (not reported here). The current thesis presents and discusses results of SIPS mainly relating to the mother. The hypotheses examined here are that increased oily fish consumption during pregnancy will: a) increase maternal LC n-3 PUFA intake b) increase maternal LC n-3 PUFA status, c) alter maternal immunity, which may influence the developing foetal immune system in a way that would decrease atopy risk for the offspring. Pregnant women (n = 123) with high risk of having atopic offspring and with low habitual intake of oily fish (? 2/month) were randomised at 20 weeks of pregnancy to either consuming 2 portions/week of farmed salmon (n = 62) or continuing their habitual diet (n = 61) until the end of pregnancy. The women attended a clinic at weeks 20 (n = 123), 34 (n = 110), and 38 (n = 91) of pregnancy at which fasting blood samples were collected for fatty acid and immunological analysis, and a food frequency questionnaire (FFQ) was administered (at 20 and 34 weeks). At delivery, placenta and umbilical cord tissue were collected for fatty acid analysis. Mothers were followed-up at 3 months postpartum when the FFQ was administered (n = 88). Maternal plasma, peripheral blood mononuclear cell (PBMC), placenta nad umbilical cord tissue fatty acid compositions were determined by gas chromatography (GC). Maternal immune cell subsets were determined by flow cytometry (FACS); ex-vivo cytokine production by PBMC in response to stimulants (allergens, mitogen, and toll-like receptor (TLR) ligands) was determined by cytometric bead array (CBA) and FACS; and eicosanoid (prostaglandin (PG) E2) production by PBMC was determined by enzyme-linked immunosorbent assay (ELISA). Subjects complied with the salmon intervention and this increased their intakes of EPA, DHA, vitamin D and selenium. The salmon intervention prevented the pregnancy-associated depletion in LC n-3 PUFA and resulted in higher LC n-3 PUFA status in maternal plasma, maternal PBMC, placenta and cord tissue. Effects of pregnancy on many of the immune parameters assessed here were identified. However, the salmon intervention had only limited impact on maternal immunity as measured here, and thus it cannot be concluded whether the intervention would have an effect on the immune system of the offspring

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ORCID for P.C. Calder: orcid.org/0000-0002-6038-710X

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