In a landmark study, researchers Maria Makrides, Robert Gibson and colleagues have uncovered more on the benefit of dietary DHA on the neurodevelopment of preterm infants.
Infants born before 33 weeks gestation are at high risk of developmental disorders and learning disabilities. The uptake of DHA into the developing brain is greatest during the last trimester of pregnancy – and so these pre-term infants have missed out on much of the DHA they would have received in the womb.
This well-designed study was a randomised, double-blind controlled trial of around 650 infants born at less than 33 weeks gestation. These vulnerable infants were fed formula or breast milk which was either high in DHA or the standard DHA level from a few days after they were born until they reached the time when the pregnancy would have reach full term. The high DHA feed contained approximately 1% of total fatty acids as DHA (from tuna oil) and the standard feed around 0.3% DHA. Almost all the infants were breast-fed initially and many continued to be exclusively breast-fed throughout the study. The mothers who breast fed their infants were provided with HiDHA® tuna capsules with a daily dose of around 900 mg of DHA to increase the DHA levels of their milk.
The study showed that by the time the pre-term infants reached their estimated due date, body levels of DHA (indicated by red blood cell membrane levels) was elevated in the high DHA group compared with standard DHA group (6.8 versus 5.2).
At 4 months (from estimated due date), the high-DHA group exhibited better visual acuity than the control group.
After 18 months of follow up the trial detected a benefit of the high DHA diet in girls but not boys using a Mental Development Index which evaluates memory, habituation, problem solving, early number concepts and language. Post hoc analyses demonstrated that the frequency of mild mental delay in smaller infants (weighing less than 1250g at birth) was reduced by about 45% in the high DHA group. Planned follow up at 7 years will be important with this group.
The conclusions?
The DHA requirement of preterm infants may be higher than currently provided by pre-term formula or the breast milk of Australian women.
Milk exceeding 1% DHA (3 times the usual level) may be required for pre-term infants to increase their DHA status to levels seen in term infants.
A DHA dose of 3 times the usual level in breast milk improves the mental development of infant girls born earlier than 33 weeks gestation.
Smithers LG, Gibson RA, McPhee A, Makrides M. Higher dose of docosahexaenoic acid in the neonatal period improves visual acuity of preterm infants: results of a randomized controlled trial. Am J Clin Nutr. 2008 Oct;88(4):1049-56.
Smithers LG, Gibson RA, McPhee A, Makrides M. Effect of two doses of docosahexaenoic acid (DHA) in the diet of preterm infants on infant fatty acid status: results from the DINO trial. Prostaglandins Leukot Essent Fatty Acids. 2008 Sep-Nov;79(3-5):141-6.
Makrides M, Gibson RA, McPhee AJ, Collins CT, Davis PG, Doyle LW, Simmer K, Colditz PB, Morris S, Smithers LG, Willson K, Ryan P. Neurodevelopmental outcomes of preterm infants fed high-dose docosahexaenoic acid: a randomized controlled trial. JAMA. 2009 Jan 14;301(2):175-82.