Taking Fish Oils During Late Pregnancy Reduces Childhood Asthma

A Danish study reports that children whose mothers who took high doses of fish oils during the last three months of pregnancy were about 30% less likely to develop asthma by age three.  16.9% of children of mothers who took fish-oil capsules developed asthma by age three, compared to 23.7% of children of mothers who took placebo capsules containing olive oil.

What on earth prompted the researchers to even think of such an experiment?  It turns out that there was some logic behind it.   Two relevant facts are; 1) chronic inflammation in the lungs and airways contribute to the development of asthma, and 2) the fatty acids in fish oils are known to reduce inflammation.  Put these two together, and the experiment seemed like a good idea.

The researchers say it's too early to recommend that all pregnant women take fish-oil capsules during pregnancy.  For one thing, the doses used in this experiment were high; 2.4 grams 0f fish-oil per day, or about 15-20 times the amount found in a normal U.S. diet.  It's not known whether lower doses might be just as effective.  Nor is it known whether the results would be better (or worse) if the women had taken the fish oils throughout pregnancy, instead of just in the last trimester.

Also, consider this: the beneficial effects of fish-oils on asthma were demonstrated only because the researchers were looking for an effect on asthma as their experimental endpoint.  Could there be negative side effects of high doses of fish oils that weren't found because they weren't looked-for?  I'm not saying that there are; I'm just making the point that it's hard to prove complete safety of a drug or treatment because there are always a lot of possibilities to test.  You won't find what you don't look for.

In the long run, the real importance of the current findings may be that they encourage further research leading to a much more targeted approach to preventing asthma than just ingesting large doses of fish oils.  It's a start.