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Intake of n-3 polyunsaturated fatty acids in childhood, FADS genotype, and incident asthma

Talaei M, Sdona E, Calder P, Jones L, Emmett P, Granell R, Bergström A, Melén E, Shaheen S (2021) The European respiratory journal Jan 28;2003633 doi: 10.1183/13993003.03633-2020. Online ahead of print. 

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Abstract:

Longitudinal evidence on the relation between dietary intake of n-3 (omega-3) very long-chain polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in mid-childhood and asthma risk is scarce.  We aimed to investigate whether a higher intake of EPA and DHA from fish in childhood is associated with a lower risk of incident asthma.

In the Avon Longitudinal Study of Parents and Children, dietary intakes of EPA and DHA from fish were estimated by food frequency questionnaire at 7 years of age. We used logistic regression, controlling for confounders, to analyse associations between intake of EPA and DHA (quartiles) and incidence of doctor-diagnosed asthma at age 11 or 14 years, and explored potential effect modification by a fatty acid desaturase (
FADS) polymorphism (rs1535). Replication was sought in the Swedish BAMSE birth cohort.

There was no evidence of association between intake of EPA plus DHA from fish and incident asthma overall (n=4543). However, when stratified by 
FADS genotype, the odds ratio (95% confidence interval) comparing top versus bottom quartile amongst the 2025 minor G allele carriers was 0.49 (0.31-0.79) (p-trend 0.006), but no inverse association was observed in the homozygous major A allele group (odds ratio 1.43, 95% confidence interval 0.83-2.46, p-trend 0.19) (p-interaction 0.006).

This gene-nutrient interaction on incident asthma was replicated in BAMSE.In children with a common 
FADS variant, higher intake of EPA and DHA from fish in childhood was strongly associated with a lower risk of incident asthma up to mid-adolescence.

FAB RESEARCH COMMENT:

This study shows that for some children and adolescents, their risks of asthma are significantly lower if their diet provides higher intakes of the long-chain omega-3 fatty acids EPA and DHA from fish and seafood.

Importantly, this was only true for children with a particular genotype, which previous research has already shown to be associated with poorer conversion of short- to long-chain omega-3 (and omega-6) fatty acids within the body.

While short-chain omega-3 (and omega-6) fatty acids are found in vegetable and seed oils, their conversion within the body into the longer-chain forms - which are biologically essential for immune, cardiovascular and brain health - is limited by many factors, including genetic individual differences.  

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