This section is under preparation and will be included in the next issue.
The n-3 and n-6 essential fatty acids alpha linolenic acid and linoleic acid are the precursors of the n-3 and n-6 longchain polyunsaturated fatty acids (LCPUFA). Controversy exists over whether LCPUFA are essential nutrients for preterm infants who may not be able to synthesise sufficient amounts of LCPUFA to satisfy the needs of the developing brain and retina. The aim of this review is to assess whether supplementation of infant formula with LCPUFA is safe and of benefit to preterm infants.
Trials were identified by MEDLINE and by checking reference lists of relevant articles and conference proceedings.
All randomised trials of formula supplemented with LCPUFA and with clinical endpoints were reviewed.
Eight randomised trials were identified. Five were assessed as being of high quality and one is awaiting assessment. Problems with the remaining two included a change in assessment methodology mid-study (Memphis 1996) and assessment methodology that deviated from generally accepted international standards (Bologna 1996).
Studies from Dallas (Uauy et al 1990, Birch et al 1992, Hoffman & Uauy 1992, Uauy et al 1994) and Memphis (Carlson et al 1991, Carlson et al 1992, Carlson et al 1993, Werkman & Carlson 1996) suggest that early visual development is better in formula-fed infants who receive a LCPUFA supplement compared with those fed standard formula. However, the effects were not long-term, with no differences detected between groups after 4 months of age. The Bologna group (Fadelli et al 1996) reported some differences in the visual evoked potential at 3 months post-term but their methodology was questionable making interpretation of the data difficult. In the largest study (the Mead Johnson study, Hansen et al 1997), no difference in visual acuity was demonstrated between LCPUFA supplemented and control infants at 2 and 4 months post-term. The Memphis studies used the Fagan Infantest (Fagan 1970) to measure infant development and demonstrated lower novelty preferences (possibly predictive of lower intelligence) in preterm infants supplemented with LCPUFA. However, the supplemented infants had more looks at the novel stimulus and each look was of shorter duration which may represent more rapid visual information processing. Normalised weight (expressed as SD from the mean for age) was lower in preterm infants who were fed supplemented formula in the Memphis studies. No difference in growth between supplemented and control infants was documented in the Dallas, Bologna, Alberta (Clandinin et al 1997) and Wyeth (Vanderhoof et al 1997) studies while the Mead Johnson study documented higher weights in supplemented infants compared with controls at two months post-term. The Dallas study documented little effect of LCPUFA supplements on bleeding time and membrane fragility.
No long-term benefit has been demonstrated for preterm infants receiving formula supplemented with LCPUFA. There is some evidence that n-3 LCPUFA supplementation of formula increases the early rate of visual maturation in preterm infants. Supplementation of formula with n-3 and n-6 LCPUFA does not impair the growth of preterm infants.