Omega-3 fatty acid is early boost for female preemies

A triple dose of DHA, docosahexaenoic acid, given to infants born six weeks or more premature boosts brain development in girls but doesn’t seem to help boys, tests at 18 months of age show. Australian researchers report the findings in the Jan. 14 Journal of the American Medical Association.

DHA is a long-chain omega-3 fatty acid, one of a suite of nutrients needed for brain development. More than half of the brain is fat, and roughly one-fourth of that fat is DHA. The best sources of DHA are fish such as tuna, herring and salmon, and some organ meats. The human body can also assemble DHA from shorter fatty acid chains found in vegetable matter, such as flax oil, canola oil, leafy green vegetables and walnuts.

But fetuses cannot do this assembly, relying instead on the mother to provide DHA intact via the placenta.

Because premature infants are often brought into the world before their brains have fully developed, some may lack adequate DHA while their brains are still growing. Breast milk and infant formula contain DHA, but some scientists theorize that the amount may be insufficient for building brain matter in preemies.  

The Australian scientists hypothesized that adding DHA to the diet of a preterm infant could improve mental development in such kids.

The new findings, from the largest trial to test the supplement randomly in preterm babies, bolster that hypothesis.

“We think the level of DHA used in [this] study should become the new ‘gold standard’ for preterm infants, whether it is supplied through breast milk or infant formula,” says study coauthor Maria Makrides, a nutritionist at the Women’s and Children’s Health Research Institute in North Adelaide, Australia.

Makrides and her colleagues identified 657 premature infants born at 23 to 33 weeks gestation — roughly 5 1/4 to 7 1/2 months into a pregnancy — at five medical centers across Australia. The babies were randomly assigned to get either a typical amount of DHA, as found in breast milk or formula, or a dose triple that amount. In bottle-fed babies, half received regular formula and half received formula fortified with added DHA. Breast-feeding mothers took six capsules daily, with half the women getting fish oil and the others soy, which doesn’t add any DHA. The scientists tested the formula and breast milk to ascertain DHA levels.

Each mother was instructed to maintain her assigned regimen until her preterm baby reached its expected birth date.

The researchers examined each baby at 18 months from the child’s due date, using standard cognitive and behavioral tests that measure the baby’s alertness, curiosity, ability to do simple tasks for a reward and other behavior. Girls receiving extra DHA either in formula or breast milk scored higher on the tests and were 57 percent less likely to have a mild delay in mental development and 83 percent less likely to have a severe delay, compared with girls not getting the supplement.

Boys didn’t show any cognitive benefit from the DHA supplements.

The researchers adjusted the data to account for differences between the groups in gestational age at delivery, gender, education level of the mother and birth order.

“This is a very well-designed and well-executed study,” says Kanwaljeet Anand, a physician and neurobiologist at the University of Arkansas for Medical Sciences in Little Rock. Differences in children’s development at age 18 months “are actually quite significant,” he says.

A higher score on these cognitive tests predicts a different trajectory for the female children receiving DHA supplements, Anand says. For example, children with higher scores may be more likely to go to college than the others, he says.

Anand serves on two advisory committees to the Food and Drug Administration, which is among several bodies that make recommendations for use of supplements such as DHA. “I think these results are quite compelling,” he says. “I will be bringing this up with the other committee members.”

Meanwhile, the male-female finding remains puzzling, Makrides says. Boys have a higher metabolic rate and thus may burn more DHA as energy. “Boys may have a higher requirement for DHA,” she says.

The Australian group plans to monitor the children for seven years.