The omega-3 fatty acid called DHA – which occurs in significant amounts only in fish oil and mothers’ milk – dominates the structures of human brains and retinas, and is essential to their functioning.

This has led to decades of research designed to determine whether mothers’ intake of DHA enhances the development of their children’s brains and vision.

There is substantial evidence that higher fish or fish oil intake by mothers and infants -- or use of infant formulas fortified with DHA -- can yield developmental benefits, although the results have been mixed. A new study from Australia adds significant new evidence that infants’ brains benefit when their mothers take fish oil.

It also indicates a down side to excessive consumption of the omega-6 fatty acids consumed in gross excess by most Americans, which compete with the omega-3s in fish oil for inclusion in human cell membranes. Omega-6 fatty acids are abundant in most vegetable oils (except olive, macadamia, and hi-oleic sunflower oils) and in the packaged and restaurant foods in which they are typically used.

Researchers at the University of Western Australia conducted a well-designed (double-blind, randomized placebo-controlled) clinical trial among 83 non-smoking women who agreed to eat no more than two portions of fish per week.

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Some of the participating women received placebo capsules containing four grams of olive oil, while the others were given capsules containing four grams of fish oil, including 2.2 grams of omega-3 DHA and 1.1 grams of omega-3 EPA.

The supplement regimen began at 20 weeks after conception, and continued until delivery.

Their infants were examined and tested when they were 2 1/2 years old, to evaluate their language skills, behavior, practical reasoning capacity, and hand-eye coordination.

Results favor fish oil and put omega-6 fats in a poor light

The children of mothers who’d taken fish oil supplements displayed significantly better hand-eye coordination, scored higher on measures of vocabulary and language comprehension, and the average phrase-length of their speech was longer.

These findings persisted after the researchers took into account other potentially influential factors, including the mother's age and the duration of breast feeding.

As the researchers said, “Maternal fish oil supplementation during pregnancy is safe for the fetus and infant, and may have potentially beneficial effects on the child's eye and hand coordination.”

It was clear the omega-3s in the fish oil were responsible, since improved good hand-eye coordination also correlated with high levels of omega-3s in umbilical cords at birth.

And it is important to note that the children with higher tissue levels of omega-6 fatty acids had the lowest scores: a finding that offers further evidence that these nutrients can be counterproductive when consumed in excess, as is usual in developed countries.