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Omega 3 intake during pregnancy and allergic disease in offspring.

Best KP, Gold M, Kennedy D, Martin J, Makrides M. 2016. Omega-3 long chain PUFA intake during pregnancy and allergic disease outcomes in offspring; a systematic review and meta-analysis of observational studies and randomized trials. Am J Clin Nutr 2016; 103:128-143.

The cause of the increasing worldwide prevalence of allergic disease is not fully understood; however, it is widely accepted that it is partly attributable to a changing environment, such as lifestyle factors and diet. Dietary changes in consumptions of different fats have reportedly changed from equal balance of omega-6 ([OMEGA]6) polyunsaturated fatty acids (PUFA) and omega-3 ([OMEGA]3) PUFA to almost 30:1 ratio ([OMEGA]6: [OMEGA]3) in some Western cultures. These dietary changes are said to parallel the increase of allergic and atopic disease, including atopic eczema, IgE-mediated rhino-conjunctivitis, and IgE-mediated allergic asthma, raising the hypothesis that this imbalance may have a causal role.

Previous clinical and animal studies have suggested an influential effect of dietary [OMEGA]3 PUFAs in early life on immune system development and function; however, investigations on clinical benefit have been conflicting. The current systematic review and meta-analysis aimed to review the role of prenatal [OMEGA]3 PUFA dietary exposure in observational studies and prenatal [OMEGA]3 PUFA supplementation in randomised controlled trials (RCTs), limiting the review to exposures or interventions commencing in the intra-partum period, in an attempt to better understand the effect on the developing foetus.

A comprehensive search was undertaken across numerous databases to identify studies for inclusion in the review. The review included prospective studies conducted in humans, including longitudinal observational studies and RCTs, with observational studies included if they examined an association between maternal fish Q3 PUFA intake during pregnancy and clinical outcomes of allergic disease or sensitisation in the offspring. Participants were pregnant women, regardless of gestation, with no restriction placed on the atopic predisposition of the women, their offspring, or age at follow-up. Studies of maternal D3 supplementation or consumption in the postnatal period only were excluded. Meta-analysis was only considered for RCTs with comparable timing of outcome assessment. The primary outcome investigated was the incidence of atopic disease, (IgE-mediated allergic disease) based on clinician diagnosis or parent report of either symptoms of allergic disease or clinician diagnosis, and/or sensitisation in the offspring during infancy, childhood or adolescence, defined as positive skin-prick test or IgE serology indicative of sensitisation.

Of the 1133 publications identified in the original search, a total of 13 publications from 10 prospective cohort studies and 7 publications representing 5 unique randomised controlled trials (RCTs) were included for analysis. Three of the RCTs were combined in a meta-analysis. Dietary fish exposure varied between women and trials from 83 g/week to 46 g/day. Four of the RCTS included fish-oil capsules as the intervention, varying in dose and composition from 900 to 3700 mg of total D3 PUFAs/day. The other RCT supplied women with 2 x 150 g portions of farmed salmon per week, equivalent to 3450 mg [OMEGA]3 PUFA/week. The timing of the interventions commenced between 20 and 30 weeks gestation and mostly ceased at the delivery of the infant, with one RCT continuing supplementation for 3.5 months postpartum.

A protective association was found in 8 of the 13 observational studies between increased prenatal D3 PUFA or maternal dietary fish intake and incidence of one or more allergic disease symptoms in the child, with a trend towards a protective association on incidence of eczema and wheeze or asthma. Of the 7 publications regarding the RCTs, 5 reported a protective effect on one or more clinical outcomes of allergic disease or sensitisation; however, a protective association trend was only observed for eczema and not wheeze or asthma, or allergic rhino-conjunctivitis.

Authors concluded that these results are suggestive that increased prenatal intake of [OMEGA]3 PUFAs may be of benefit in reducing the extent and/or severity of some allergic diseases. However, due to the inconsistent results, the association of maternal [OMEGA]3 PUFA and childhood allergic disease cannot be unequivocally confirmed or rejected. The limited number of well-powered, well-designed RCTs with long term follow-up is a challenge in establishing a better understanding of the potential protective effects of maternal D3 intake. Furthermore, the challenges of dietary estimation through questionnaires are well established and can contribute to bias and variations in results. With increasing incidence of allergic disease, the opportunity for primary prevention interventions to reduce risk through dietary intervention is of significant importance. The promising potential of [OMEGA]3 PUFAs requires further evidence to better understand the optimal dose and duration of intervention, and to conclusively establish benefits on childhood allergic outcomes.

Jodie Tester

These abstracts are brief summaries of articles which have appeared in recent issues of herbal medicine journals, some of which may be held in the NHAA library.
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Author:Tester, Jodie
Publication:Australian Journal of Herbal Medicine
Article Type:Report
Geographic Code:8AUST
Date:Jun 1, 2016
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