Omega-3 and the Special Case of the Preterm Infant
The essentiality of the long chain omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid for infants’ and children’s brain development is so well established that the strict European Food Safety Authority recently approved a health claim that DHA contributes to normal brain development. DHA starts to accumulate in the brain during the third trimester from about 27 weeks’ gestational age. The fetus obtains DHA from the mother’s circulation, and after birth from breast milk or formula, which should contain DHA. Infants born prematurely are at particular nutrition risk as they do not receive the large transfer of nutrients that occurs in the last weeks of pregnancy (see review on omega-3 requirements in pregnancy from Coletta, Bell and Roman). In a recent review, Brenna discusses omega-3 fatty acids in light of the special needs of preterm infants.
One of the issues that has plagued research into essential fatty acids in the past, and may also be a problem today, is that a deficiency in omega-3 fatty acids does not affect growth. Growth faltering is the main hallmark of a failure to thrive, the most obvious means for pediatricians to monitor the development of children. Animal models show that despite equivalent growth with young animals fed DHA-replete diets, DHA-deficient animals have poor cognitive and visual development, including adverse behavioral responses (Brenna summarizes various animal studies). Therefore, DHA-deficient infants may present with developmental or behavioral problems despite normal growth. This is in contrast to omega-6 PUFA deficiency, which also manifests itself in poor infant growth. Delays in cognitive and behavioral development are more difficult to detect or measure.
Both ARA and DHA are now present in infant formulas. While it is possible for infants to synthesize small amounts of these long chain fatty acids from their shorter-chain precursors from vegetable oils, as Salem and colleagues report, the amounts made by the body are regarded as too small to support the large increases in brain DHA levels needed for normal cognitive and visual development. Fleith and Clandinin also state that the higher relative rate of growth of preterm infants means that their needs for EPA and DHA are greater than for term infants: the average newborn takes 4 months to double its weight, but a doubling is also achieved between 27 and 32 weeks of pregnancy, and between 32 weeks and birth in the fetus, a much shorter period of time. Accumulation of DHA into the retina in the last trimester of pregnancy occurs more rapidly than into the brain, and preterm infants may require a greater supply of DHA to support visual development.
There is strong evidence that DHA is particularly helpful in supporting the normal development of preterm infants. Milk fed to preterm infants should contain adequate levels of DHA, and the need for DHA may be higher than is supplied either with breast milk or with infant formula developed for term infants. Expectant mothers that have adequate DHA intakes may also reduce their risk of preterm birth a little, as TalkingNutrition has reported earlier. More so than term infants, preterm infants may have a greater need for DHA.
J Thomas Brenna. Long-chain polyunsaturated fatty acids and the preterm infant: a case study in developmentally sensitive nutrient needs in the United States. Am J Clin Nutr ajcn103994; First published online January 20, 2016. doi:10.3945/ajcn.114.103994 http://ajcn.nutrition.org/content/early/2016/01/20/ajcn.114.103994.short
Brenna JT. Animal studies of the functional consequences of suboptimal polyunsaturated fatty acid status during pregnancy, lactation and early post-natal life. Matern Child Nutr. 2011 Apr;7 Suppl 2:59-79. doi: 10.1111/j.1740-8709.2011.00301.x. http://www.ncbi.nlm.nih.gov/pubmed/21366867
Coletta JM, Bell SJ, Roman AS. Omega-3 Fatty Acids and Pregnancy. Reviews in Obstetrics and Gynecology. 2010;3(4):163-171. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3046737/
Fleith M, Clandinin MT. Dietary PUFA for preterm and term infants: review of clinical studies. Crit Rev Food Sci Nutr. 2005;45(3):205-29. http://www.ncbi.nlm.nih.gov/pubmed/16048149
Salem N Jr, Wegher B, Mena P, Uauy R. Arachidonic and docosahexaenoic acids are biosynthesized from their 18-carbon precursors in human infants. Proc Natl Acad Sci U S A. 1996 Jan 9;93(1):49-54. http://www.ncbi.nlm.nih.gov/pubmed/8552667