Higher DHA Intakes in Preterm Infants and Visual Acuity
Smithers LG et al., Am. J. Clin. Nutr. 88:1049-1056, 2008.
Women’s and Children’s Health Research Institute and Neonatal Medicine, Children, Youth and Women’s Health Service, North Adelaide, Australia.
Randomized control trials have indicated an improvement in visual acuity and overall retinal sensitivity in infants receiving infant formula enriched with DHA (docosahexaenoic acid) + arachidonic acid. The last trimester of gestation is a particularly active period for the accretion of DHA into retinal and neural tissues. The present study assessed visual responsiveness of pre-term infants (less than 32 weeks gestation) fed human milk and formula with a high DHA concentration (1% of milk fat) as compared to infants fed human milk and formula containing DHA at a level of approximately 0.3% of milk fat (standard practice). Both groups received similar concentrations of arachidonic acid (0.43-0.45% of total milk fat). The primary end-point measurement was a measure of visual acuity by sweep visual evoked potential (VEP) acuity at 4 months corrected age.
Visual acuity in the high-DHA group did not significantly differ from the control (low DHA) group at 2 months corrected age. However, the high-DHA group exhibited a significantly higher acuity at 4 months corrected age (mean value of 9.6 cycles per degree as compared to 8.2; the measured acuity was ultimately higher by 17% in the high-DHA group. The authors conclude that the DHA requirement (optimal intake) for preterm infants may be higher than that currently provided by preterm formula or human milk in Australian women.
Dr. Holub's Comments:
These results from Australia emphasize the importance of ongoing clinical trials in both preterm and full-term infants with varying levels of DHA (with varying levels of arachidonic acid) to establish the optimal level of DHA to support neuronal and visual functioning in infants. In this regard, it is of interest to note that a recent study of the concentrations of docosahexaenoic acid in human breast milk worldwide showed dramatic differences across countries ranging from values of 0.12-0.20% of milk fat in Canada and the USA and up to concentrations of 0.99% and 1.40% in Japan and the Canadian Arctic, respectively (Brenna et al., 85:1457-1464 (2007)). The mean concentrations of DHA in breast milk (from 65 studies worldwide of 2474 women) was 0.32% by weight of milk fat as DHA and 0.47% in the case of arachidonic acid.