Writing in the New England Journal of Medicine (NEJM), the international team behind the study reported that mothers who took supplements containing high doses of omega-3 fatty acids in the last three months of pregnancy had a lower incidence of persistent wheeze or asthma, and infections of the lower respiratory tract, in their children.
Led by professor Hans Bisgaard from the University of Copenhagen in Denmark, the randomised trial followed more than 700 Danish women and their children – finding that the risk of childhood asthma, wheezing and respiratory infection in the first five years of life was lowered by almost one third in women assigned to receive the marine derived omega-3 supplement.
"We've long suspected there was a link between the anti-inflammatory properties of long-chain omega-3 fats, the low intakes of omega-3 in Western diets and the rising rates of childhood asthma," said Bisgaard. "This study proves that they are definitively and significantly related."
"Asthma and wheezing disorders have more than doubled in Western countries in recent decades," he added. "We now have a preventative measure to help bring those numbers down."
In a commentary also published in NEJM, Dr Christopher Ramsden from the National Institute on Aging in Baltimore in the US state of Maryland, suggested that the results or the trial are ‘highly promising’ but warned that the dose of fatty acids used in the trial (2.4 grams per day) is around 15-20 times higher than average intakes.
“It is imperative to ensure that this dose had no adverse effects on behaviour, cognition or other long-term outcomes,” he wrote – noting that that further work could also address whether lower doses are equally effective.
The research team randomised 736 women at 24 weeks of pregnancy to receive daily supplementation with either 2.4 grams of omega-3 (55% EPA and 37% DHA in triacylglycerol form supplied by Croda Health Care) or a placebo of olive oil (72% omega–9 oleic acid and 12% omega−6 linoleic acid, Pharma-Tech A/S).
They then followed up 695 of the offspring for three years, while investigators and parents were blinded to treatment assignments, and a further two years when the only the investigators remained unaware.
Results showed that the risk of persistent wheeze or asthma in children born to women who were given the omega-3 supplement in late pregnancy was 31% lower than in those born to women in the placebo group.
Furthermore, they found that that supplementation was significantly linked to a reduced risk of lower respiratory tract infections in offspring (31.7% v 39.1%) but not with a statistically significant reduction in asthma exacerbations, eczema, or allergic sensitisation.
The trial also showed that women with low blood levels of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) at the beginning of the study benefitted the most from the supplements. For these women, it reduced their children's relative risk of developing asthma by 54%.
"Identifying these women and providing them with supplements should be considered a front-line defense to reduce and prevent childhood asthma,” said professor Ken Stark from the University of Waterloo, Canada – who led the lab testing team.
Dr Ramsden added that the fact a preventive effect of omega-3 was seen most in children whose mothers had low baseline blood levels of EPA and DHA was “a particularly salient finding.”
Writing in his commentary, he agreed that the study also highlights the importance of measuring baseline EPA and DHA levels in future trials and public health initiatives.
“These observations (...) point toward a precision-medicine approach in which factors such as blood levels of fatty acids, genotype, and parental history of asthma could potentially be used to tailor interventions to those most likely to benefit,” he suggested.
Source: New England Journal of Medicine (NEJM)
Published online ahead of print, doi: 10.1056/NEJMoa1503734
“Fish Oil–Derived Fatty Acids in Pregnancy and Wheeze and Asthma in Offspring”
Authors: Hans Bisgaard, et al