Dietary Fatty Acids in Growth and Development
Gibson, Robert A., and Makrides, Maria, (2000) Dietary Fatty Acids in Growth and Development. Malaysian Journal of Nutrition, 6 (2). pp. 171-179. ISSN 1394-035X
Official URL: http://nutriweb.org.my/publications/mjn006/mjn6n2_art4.pdf
Child Nutrition Research Centre South Australia
Flinders Medical Centre South australia
A newborn infant will double his/her weight in the first 3 months of life and double it again in the next year. Such a rapid growth rate demands adequate nutrition. Fat is a vital source of energy for the growing infant. In breast milk for example, 50% of the energy is in the form of fat. The fat of breast milk contains a full complement of polyunsaturated fatty acids (PUFA), including the two essential PUFA, linoleic acid (LA, 18:2 n-6) and a-linolenic acid, (ALA, 18:3 n-3) but also a range of long chain (LC) PUFA that have been shown to have benefits for both preterm and term infants. Until recently, infant formulas contained LA and ALA only, and this was thought to provide adequate fat nutrition since formula fed infants grew as well as breast-fed babies. LCPUFA are increasingly being added to infant formulas as the technical challenge relating to identifying sources that are stable and hence safe for infants have been overcome. The scope of this paper is to review some of the latest information available in the field of LCPUFA in infant nutrition, growth and development. While LA and ALA have biological activity in their own right, their activity is enhanced when they are converted to 20 and 22 carbon metabolites (LCPUFA) as they are readily incorporated into cell membranes and can be precursors of the potent hormones known collectively as eicosanoids. The main LCPUFA of interest during infancy are docosahexaenoic acid (DHA, 22:6 n-3) and arachidonic acid (M, 20:4 n-6). DHA and AA are found in many non-vegetable foods (breast milk, fish, meat, eggs) so can be obtained directly from the diet as well as by conversion of LA and ALA in the body. Growth is one of the most sensitive indicators of adequate nutritional status in infants and young children and for this reason is considered to be of key importance in all nutritional interventions. In the field of LCPUFA research the growth of infants randomly allocated to placebo or LCPUFA supplemented formulas has been used as a primary assessment of safety. One of the earliest and most cited trials involving preterm infants allocated to either a placebo, unsupplemented formula or one supplemented with a high EPA fish oil claimed that normalized weight and length of fish oil supplemented formula infants was less than that of infants fed unsupplemented formula at each assessment time between term and 12 months corrected age. It was postulated that low levels of AA, caused by the high n-3 LCPUFA content of the formula, were related to poor growth achievement in preterm infants. Phospholipid AA was correlated to normalized weight and length. However, it is interesting to note that more recent reports have not confirmed these findings. The failure of the later preterm studies to detect an effect of LCPUFA on growth has been suggested to be due to the balance of AA and DHA. It may also be that the growth of infants in these early studies was affected by factors other than the dietary fats. There are several studies underway to clarify this issue.
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