According to a new US review, supplementation of infant formulas with docosahexaenoic acid (DHA) and arachidonic acid (AA) improves the visual acuity of infants up to 12 months old.
This meta-analysis was based on 19 randomized controlled trials that assessed the efficacy of long-chain polyunsaturated fatty acid (LCPUFA) supplementation in infant formulas on the visual resolution acuity of a total of 1,949 infants in their first year of life (1). The analysis showed a significant benefit of LCPUFA supple-mentation in infant formulas on infant visual acuity at several early stages of development (namely, at two, four, and 12 months of age) when compared to non-supplemented infants. In general, trials that used doses of DHA and AA similar to those found in human milk (in a ratio of 1:1 or higher) tended to show a positive effect of supplementation. Conversely, trials that used DHA doses below 0.32% were likely to show a non-significant effect on visual acuity.
The researchers commented that the new findings confirmed the results seen in some previous meta-analy-ses in term and preterm infants (2,3). However, the new results stand in contrast to two recently published systematic reviews that failed to show a benefit of LCPUFA supplementation on visual acuity (4,5). These meta-analyses failed to combine trials that measured visual acuity in certain metrics and assessed preterm and term infants separately, which substantially reduced the power of these meta-analyses. It can be hypo-thesized that a DHA dose of 0.32% with a similar or higher AA dose, i.e. maintaining a DHA/AA ratio of at least 1:1, is sufficient for optimal visual acuity maturation, the scientists noted.
Infant formula is the sole source of energy and nutritional requirements for many infants during their first
12 months of life. The US Food and Drug Administration estimates that by one year of age, 75% of infants are formula fed (6). Differences in LCPUFAs between unsupplemented infant formula and breast milk have been hypothesized to affect infant growth and development. DHA and AA are the two main LCPUFAs that constitute the integral structural part of membranes of the cells of the central nervous system and the retina. Although human fetuses can synthesize DHA and AA from their essential fatty acid precursors after 26 weeks of gestation, the synthesis varies widely between infants, being very minimal in some (7). After birth, breast milk is the main source of LCPUFAs and their metabolites; however, the amount varies among mothers (8).