The roles of long-chain polyunsaturated fatty acids in pregnancy, lactation and infancy

Lipids are of critical importance for the fetus, infant and young child. First of all, they are a major energy source to support appropriate growth, secondly, they can provide omega-3 and omega-6 polyunsaturated fatty acids (PUFA), which are required for normal growth and maturation of numerous organ systems, most importantly the brain and eye, but that infants can not synthesize. In this review, the recent literature on these issues is summarized and consensus recommendations and practice guidelines supported by the World Association of Perinatal Medicine, the Early Nutrition Academy, and the Child Health Foundation are provided.
Alpha-linolenic acid (ALA) and linoleic acid (LA) are essential fatty acids that must be present in the diet. ALA and LA are converted to longer chain, more highly unsaturated fatty acids through enzymatic chain elongation and desaturation. In particular, ALA is converted to eicosapentaenoic acid and then to docosahexaenoic acid (DHA), whereas LA is converted to arachidonic acid (AA). DHA is a critical component of cell membranes, especially in the brain and the retina, while AA is both a membrane component and a precursor of prostaglandins and leukotrienes, potent signaling molecules. Brain accumulation of both DHA and AA starts in utero and continues during the post-natal development. It has been shown that the consumption of oils rich in LC-PUFA during pregnancy allows normal visual and cognitive development, reduces the risk for early premature birth and is associated to other important short- and long-term benefits (lower blood pressure, modulation of immune response and increase in bone mass).
Human milk always contains both AA and DHA, whereas, in the past, infant formulae had neither. However, synthesis rates of LC-PUFA from C18 precursors are insufficient to maintain stable plasma and red blood cell LC-PUFA levels in infants receiving unsupplemented formula, and LC-PUFA levels decline in infants fed unsupplemented formula compared to those fed human milk. On the basis of the results of several trials, the fetus and neonate should receive LC-PUFA in amounts sufficient to support optimal visual and cognitive development. Recent European Commission supported consensus recommendations, based on systematic literature reviews and an expert consensus process, include the advice that pregnant and lactating women should aim at achieving an average DHA intake of at least 200 mg per day. Current recommendations strongly support breastfeeding as the preferred method of feeding healthy infants and emphasize the importance of the provision of a balanced dietary intake for breastfeeding women, including a regular supply of DHA. When breastfeeding is not possible, the use of an infant formula providing DHA at levels between 0.2 and 0.5 weight percent of total fat, and with the minimum amount of AA equivalent to the contents of DHA is recommended.

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