a baby wearing glasses

photo courtesy mia_mae via Flickr.

There’s been a fair amount of research showing that pregnant women who consume fish oil and fish liver oil have babies that come out smarter.  But what, exactly, is a smart baby?  And does a smart baby necessarily grow up into a smart adult?

A few years ago, a group of Norwegian researchers published the four-year follow-up of a trial where pregnant women were given cod liver oil starting a few months into their pregnancies, and continued a few months after giving birth.  (There was, of course, a placebo group).  So the infants got fish oil both in the womb, and while breast-feeding.  The paper was published in the prestigious medical journal Pediatrics.

A full four years after their mothers had taken the supplements, cod liver oil babies and placebo babies were given IQ tests.  The IQ tests assessed what are called sequential and simultaneous processing.  Sequential processing involves remembering a string of numbers or words in order, or doing things in a particular sequence, one at a time.  Simultaneous processing is more about keeping a number of things in your head at the same time.  Face recognition, which requires us to see and recognize a number of different things all at once, is an example of simultaneous processing.

The cod liver oil babies were smarter.  They did better than the placebo babies on both sequential and simultaneous processing.

Well, that was in 2003.  Last year, another follow-up was published on the same kids, again in Pediatrics.  The question was, would the benefits to intelligence follow kids a full seven years into their lives?  As it turned out, the answer was “no.”

Disappointing?  Yes, but let’s look at the data more closely.

Many of the original cod liver oil babies had been off cod liver oil for years; many of the placebo babies had been taking it.  In fact, the two groups were statistically identical for cod liver oil consumption for the entire seven years following the original intervention.  The longer this went on, the more the original difference between the groups became a “drop in the bucket”.

There’s also always a problem with research like this through no fault of the researchers where certain groups tend to select themselves to be researched.  For example, long-term sleep studies tend to involve people who don’t have families or jobs.  Trials using experimental medications for asthma tend to attract people who can’t afford a prescription of asthma medication.

In this study, the four-year follow-up, and especially the seven-year follow-up, began to attract more and more educated and wealthier people.  As the time went on, the poorer, less-educated people began dropping out.  Yet perhaps poorer, less educated people (presumably with worse diets?) would have benefited more noticeably from the original supplementation.

That’s the fun thing about research: there’s so much we never know.

But it’s pretty clear that, at the very least, cod liver oil keeps babies smarter, for a while.  Perhaps if the cod liver oil babies had stayed on the cod liver oil, and the placebo babies had stayed on placebo, we’d still see a big difference.

The dose of cod liver oil was 2 tsp a day.  It contained 1,183 mg of DHA and 803 mg of EPA a day, as well as vitamins A and D.  The placebo (corn oil) was supplemented to contain equivalent amounts of vitamins A and D.

The Norwegian government does not currently recommend cod liver oil to pregnant women.  It does, however, recommend 1 tsp per day to all infants over 5 weeks of age.