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WASHINGTON, Dec. 29 (Xinhua) -- Women who take fish oil supplements during the last three months of pregnancy may reduce their child's risk of developing asthma by almost one third, a new study in Denmark has found.
The study, published in the Thursday's issue of New England Journal of Medicine, assigned about 700 pregnant Danish women at 24 weeks of gestation to take 2.4 grams per day of either a supplement of fish oil, or a placebo of olive oil.
Then, researchers monitored the health status of children of these women for five years, which is the age asthma symptoms can be clinically established.
It turned out that 16.9 percent of the children in the fish oil group had asthma, compared to 23.7 percent in the control group, corresponding to a reduction in risk of 30.7 percent.
However, the preventive effect was seen almost exclusively in children whose mothers had low blood levels of two long-chain omega-3 fatty acids in fish oil, known as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), at the beginning of the study. For these children, their risk of developing asthma was cut by 54 percent.
Previous research has found long-chain omega-3 fatty acids including EPA and DHA are key to regulating human immune response.
"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 lead author Hans Bisgaard, professor at the University of Copenhagen. "This study proves that they are definitively and significantly related."
Currently, up to 20 percent young children in developed countries suffer from asthma or a related disorder before school age.
"Asthma and wheezing disorders have more than doubled in Western countries in recent decades," Bisgaard said in a statement. "We now have a preventative measure to help bring those numbers down."
Christopher Ramsden of the U.S. National Institutes of Health sounded a cautious note in an accompanying editorial, saying that the dose of 2.4 grams per day provided in this trial was "approximately 15 to 20 times as high as the average U.S. intake from foods."
"Before these findings can be applied to clinical practice, it is therefore imperative to ensure that this dose had no adverse effects on behavior, cognition, or other long-term outcomes," Ramsden wrote. "Future work is also needed to determine whether lower doses are effective and whether these results can be replicated in other populations."
