Docosahexaenoic acid (DHA), which affects brain and eye development, is derived by fetuses from their mothers and accumulates in the brain primarily in the third trimester. DHA levels appear to be affected by diet, and the DHA intake of U.S. adults, including pregnant women, is very low compared to most cultures in the world, points out Susan Carlson, professor of nutrition at the KU Medical Center in Kansas City, Kan.

"Although there is individual variability within a culture, we know from worldwide studies of breast milk that women who live in countries whose diets are rich in fish and other marine sources such as Norway have much higher DHA levels in milk and probably have more DHA to transfer to the fetus than American women," she says.

Carlson; John Colombo, KU professor of psychology and associate director for cognitive neuroscience at the Life Span Institute at KU; and Kathleen Kannass, research associate at the Life Span Institute, measured the DHA levels of 70 mothers' blood when their infants were born. The researchers then followed the infants for the first two years of their lives, evaluating them on different tests of attention during the first and second years.

"The most striking thing we found was that infants from mothers who had high levels of DHA consistently showed more advanced forms of attention all the way out into the second year of life," Colombo said.

Previous studies of the effect of DHA-enhanced infant formula on infants' cognitive development were mixed, Colombo explained, because some studies showed that the effects of DHA were present at early ages but then disappeared at older ages.

In this study, toddlers were tested at 4 months, 6 months and 8 months on a simple type of visual attention, and although infants from high-DHA mothers were ahead at 4 months and 6 months, the differences disappeared at 8 months.

However, the same infants were tested again at 12 months and 18 months, when a different kind of attention, more closely related to attention span, begins to develop and the advantage for the high-DHA group reappeared. The infants with high-DHA mothers were more engaged with complicated toys and less distractible during play.

Carlson and Colombo each have been previously involved in research on DHA. In 2002, their prior research efforts helped convince the Ross Products and Mead Johnson Nutritionals infant formula companies to add the compounds to their Similac and Enfamil brand formulas.

Colombo and Carlson hope to be able to increase DHA levels in pregnant mothers through dietary or nutritional supplements and then study the development of those mothers' infants.

The study was published in the July 2004 issue of the scientific journal Child Development.

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