Over 600 infants took part in the trial, which involved randomising them to receive either a high or standard dose of DHA (docosahexaenoic acid) from day two to four of life until the infants reached their expected date of delivery. DHA intake continued after this date via the mother’s breast milk or infant formula.
Writing in the new issue of the Journal of the American Medical Association, researchers from the Women’s and Children’s Hospital and Flinders Medical Centre in Adelaide, Australia report that measures of memory, problem solving, early number concepts and language were higher in girls who had received the high dose of DHA.
“The lack of responsiveness of boys to the intervention is puzzling, and the reasons are unclear,” wrote the researchers, led by Maria Makrides.
Infants born prematurely are at a higher risk of developing learning disabilities. The study is potentially important because, according to a study published in the British Medical Journal in 2006, the number of premature births increased by 22 per cent between 1995 and 2004. The study was carried out in Denmark, but similar patterns are reported in other European countries.
Makrides and her co-workers recruited 657 infants born before 33 weeks’ gestation. The initial supplementation involved receiving either high dose DHA (approximately 1 per cent total fatty acids) or the standard dose (approximately 0.3 per cent total fatty acids). Lactating mothers of infants in the high-DHA group consumed six 500-mg DHA-rich tuna oil capsules per day. If supplementary formula was required, infants were given a high-DHA preterm formula.
Of the 657 infants enrolled, 614 completed the 18-month follow-up.
Using the Bayley Mental Development Index (MDI) to evaluate neurodevelopment, the researchers found that no overall differences were observed between the high-DHA and standard-DHA groups. When the MDI scores among girls and boys were considered, a significant increase in MDI scores was noted for girls fed the high-DHA diet than those fed the standard-DHA diet. No benefits were observed in the boys.
Furthermore, MDI scores among smaller infants (weighing less than 1.27 kg (2.8 lbs) at birth) fed the high-DHA diet were higher than that of infants fed standard-DHA, but this wasn’t statistically significant, said the researchers. MDI scores of infants over 1.27 kg at birth did not differ between groups.
“Infants ranged in gestational age from 23 to 33 weeks and, thus, had a range of nutritional stressors, organ immaturity, and [illnesses]. Despite this, the intervention was sufficiently robust to consistently elicit an improvement in the MDI scores of girls and may point the way for higher-dose interventions in future studies. Given the lack of an alternative therapy for cognitive delay in this group of infants and the apparent safety of the current dose of DHA, further studies are warranted,” concluded the researchers.
The authors stated they have no financial interests in infant formula or nutritional supplements. They do note that some of them are members of scientific advisory boards for companies such as Nestle, Fonterra, Wyeth, and Nutricia.
Source: Journal of the American Medical Association2009, Volume 301, Issue 2, Pages 175-182“Neurodevelopmental Outcomes of Preterm Infants Fed High-Dose Docosahexaenoic Acid - A Randomized Controlled Trial”Authors: M. Makrides, R.A. Gibson, A.J. McPhee, C.T. Collins, P.G. Davis, L.W. Doyle, K. Simmer, P.B. Colditz, S. Morris, L.G. Smithers, K. Willson, P. Ryan