A Danish study of 695 pregnant women is raising the possibility that fish oil supplements begun in the final three months of pregnancy may reduce the risk of asthma or persistent wheezing in offspring.
Previous research has shown that asthma is more prevalent among babies whose mothers have low levels of fish oil in their bodies. The new large-scale randomized controlled trial, published in The New England Journal of Medicine, is the first to see if supplements can actually lower the risk.
The supplements (2.4 g of omega-3’s per day) brought the risk from 23.7 percent among mothers in the placebo group who took 2.4 grams of olive oil daily down to 16.9 percent in the women who got the fish oil capsules, a 31 percent reduction according to the University of Copenhagen research team.
Supplements most beneficial in women with low levels of omega-3’s
The real benefit seemed to be exclusively among the children whose mothers started out with low levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the two omega-3 fatty acids in fish oil. Having a low level of omega-3’s may make children more vulnerable to the inflammation and heightened immune system response that is a factor in asthma.
Among the Danish women with low EPA and DHA levels, the rate of asthma and wheezing in their children was 17.5 percent when the women took fish oil during pregnancy versus 34.1 percent when they took the placebo oil.
A daily dose of 2.4 g of omega-3 fatty acids is equivalent to eating 4 ounces of salmon per day.
The findings must be tested in other parts of the world, where fish oil consumption is lower.
The World Health Organization recommends no more than 3 grams per day, in part because excessive amounts can increase the risk of bleeding, lower blood pressure, and interact with medicines or vitamins A, D and E.
It is possible that a lower dose would have sufficed, the researchers said.
Fish oil supplementation also lowered babies’ risk of lower respiratory tract infections.
But the supplements didn't seem to affect the odds of a baby or toddler developing eczema, milk or egg allergy or a severe asthma attack.
The women began taking the fish oil and olive oil capsules at the 24th week of pregnancy and continued until one week after delivery.
Until more studies are conducted in other populations, the researchers noted it would be premature to widely recommend fish oil during pregnancy.
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