02 January 2017
Bisgaard, H. et al., New Engl. J. Med., 375: 2530-2539, 2016
Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark
The prevalence of asthma and wheezing in early childhood has increased considerably in the past several years due to many environmental, dietary, and other factors. Some evidence exists to suggest that EPA/DHA omega-3 fatty acids from fish as consumed during pregnancy may offer beneficial effects for the offspring. However, the relatively small numbers of subjects used in randomized controlled trials with fish oil supplements have yielded rather inconsistent findings. Thus, the present clinical trial was conducted with a large number of pregnant women (736) wherein supplementation was initiated during the third semester of pregnancy and maintained until one week after delivery. At week 24 of pregnancy, half the women were assigned to receive 2.4 grams (2400 mgs) of supplemental omega-3 fatty acids (EPA:DHA ratio of 3:2) via capsules or a placebo supplement (olive oil) lacking EPA/DHA. Both the researchers and the participants were unaware of the type of supplement given/received. Pediatricians monitored the offspring at regular intervals (follow-up from birth to 3-5 years of age) for persistent wheeze or asthma (the primary end point) based on lung symptoms as well as infection of the lower respiratory tract based on a diagnosis of pneumonia or bronchiolitis. A total of 695 children (both groups combined) completed the follow-up.
Both capsule counts and measured blood levels for EPA/DHA (elevated in mothers receiving EPA/DHA) indicated a high degree of supplementation compliance by the participants (greater than 80 %). Follow-up revealed that 20 % of the 695 children (136) developed persistent wheeze or asthma. The risk of persistent wheeze or asthma was significantly lower (by 31 %) in the omega-3 group (16.9 % prevalence) as compared to the placebo (control) group (prevalence of 23.7 %). The protective effect of the EPA/DHA supplementation appeared to be more pronounced (reduction of 54 % in wheeze/asthma) in the offspring from those mothers who were in the bottom third with respect to blood levels of EPA/DHA at entry. In addition, maternal omega-3 supplementation was associated with a significant reduction in the risk of lower respiratory tract infections (by 25 %) in the offspring during follow-up to 3-5 years of age.
Dr. Holub’s Comments :
It is noted that the intake of EPA/DHA via daily supplementation in the omega-3 group would be approximately 10 times higher than is typical in the Danish diet and 20 times that which our lab previously reported (average of 117 mgs/day) in pregnant Canadian women (J. Nutr.,135: 206-211 (2005). While the present study was not designed to delineate the mechanisms underlying the beneficial effects of EPA/DHA, both of these omega-3 fatty acids are known to favourably modify the generation of bioactive products resulting in a reduced inflammatory impact. The attenuation of the severity of asthma via reduced inflammation likely includes the generation of various lipid mediators such as E-series resolvins from EPA which serve to support the resolution of inflammation. Future studies which evaluate the effect of varying intakes and ratios of EPA and DHA by pregnant mothers on the prevalence of respiratory disorders in their children will be of considerable interest with the potential to improve health outcomes in the young as well as reducing health care costs.