Study suggests that arachidonic acid should exceed the amount of docosahexaenoic acid in infant formula used for premature babies

Rob Winwood

October 6, 2015

A new study concerning the nutritional supplementation of polyunsaturated fatty acids in formula milk for premature babies has demonstrated that a treatment group consuming a 2:1 ratio of ARA (arachidonic acid) to DHA (docosahexaenoic acid) displayed much better psychomotor development and higher blood levels of PUFAs than a 1:1 group. The work provides further evidence of the importance of ARA for the neurological development of premature babies.

It is generally acknowledged that the intake of the omega 3 fatty acid DHA and the omega 6 fatty acid ARA by premature babies plays an important role in determining their rate of neurological development. However, recent studies have focused more on the content of DHA rather than ARA in infant formula. Furthermore, it is also well-established that the biochemical pathway resulting in the endogenous production of both ARA and DHA (from alpha linolenic and linolenic acid respectively) utilizes the same enzymes. Hence, it is logical that the ratio of ARA to DHA in formula would be very important, but this had not yet been investigated prior to the current study (1).

The European Society of Paediatric Gastroenterology, Hepatology and Nutrition (2) suggests that formula for premature babies should contain 0.2–0.5% (of total fatty acids) of DHA and 0.3–0.7% (of total fatty acids) of ARA. However, most commercial formulae for premature babies contain a 1:1 ratio of DHA to ARA. The percentage of ARA in human breast milk globally is relatively small, 0.24–1.0% (expressed as fatty acids) and is unresponsive to maternal supplementation.

The current study by Alshweki et al. (1) was conducted in Spain with premature babies who had a birth weight of below 1500 g and/or who were born prior to 32 weeks’ gestation. There were three groups: infants fed formula containing 1:1 DHA to ARA, infants fed formula containing 1:2 DHA to ARA and a control group of entirely breastfed infants. The only difference between the formulae in the two interventions was the level of ARA. The DHA level was 0.33% of the total fatty acids. The primary outcome measure was psychomotor development at 24 months of age using the Brunet-Lézine scale. The scores were almost identical for the 1:2 DHA to ARA group and the control breastfed group, with the two being significantly better than those for the 1:1 DHA to ARA group. This study therefore appears to demonstrate that formula for premature babies should contain a rich ratio of DHA to ARA.

The study revealed no difference between the three groups in terms of weight, length and head circumference at 6 and 12 months. Nor were there any differences between visual and auditory evoked potentials (VEP/AEP), but this was expected as these factors are thought to be related to DHA rather than ARA.

In a further study, baboon neonates fed formula containing an ARA to DHA ratio of less than one (0.96% DHA:0.64% ARA) presented reduced levels of ARA in all analyzed areas of the brain (3).

In infant development, ARA works in combination with DHA, with both LCPs (long¬ chain polyunsaturated fatty acids) joining forces like twins, each providing unique but also intertwined benefits. However, this recent study (1) suggests that for premature babies, ARA is of particular significance.


  1. Alshweki A, Munuzuri AP, Bana Am et al., “Effects of different arachidonic acid supplementation on psychomotor development in very premature infants; a randomized controlled trial”; Nutritional Journal 2015; 14:101 DOI 10.1186/s12937-015-0091-3.
  2. Agostoni C, Buonocore G, Carnielli VP, “Enteral nutrient supply for preterm infants: commentary from the European Society of Paediatric Gastroenterology, Hepatology and Nutrition Committee on Nutrition”, J Pediatr Gastro Enterol Nutr 2010; 50: 85.
  3. Hsieh AT, Anthony JC, Diersen-Schade DA et al.,“The Influence of moderate and High Dietary Long Chain Polyunsaturated Fatty Acids (LCPUFA) on Baboon neonate Tissue Fatty Acids“, Pediatric Research 2007, 61:537-545.