Evidence for infant formulas providing both docosahexaenoic acid and arachidonic acid

Although the importance of fatty acids for human health and wellbeing was initially recognized almost 90 years ago ^1,2, it is during the last three decades that there has been considerable interest in the roles of long chain polyunsaturated fatty acids (LCPUFAs) in infant growth and development ^3-6. However, despite there now being a wealth of information on the functional roles of docosahexaenoic acid (DHA) and arachidonic acid (ARA) from cellular, animal and human studies, policies relating to dietary intakes of DHA and ARA in early life continue to lack a consensus across key policymakers ^7,8 and a pivotal issue relates to whether infant formulas should contain both DHA and ARA.

Relevant biological factors

In early life there is biological evidence that human development recognizes the importance of DHA and ARA as necessary structural and functional nutritional metabolites for optimal growth and development. For example, DHA and ARA are always available in breast milk whereas in cow’s milk, goat milk, soya- and rice-based beverages DHA and ARA are either not detected or only present in trace amounts ⁹. The need for an adequate supply of these fatty acids during pregnancy is evidenced by an active transport mechanism for the transfer of these fatty acids across the placenta from the mother to the fetus ^10,11. In the postnatal period, DHA and ARA are released from maternal lipid stores to increase the DHA and ARA content of breast milk during lactation, and this process is dependent upon maternal dietary intake of DHA and ARA ^12,13.

Seminal work by Manuela Martinez demonstrated that, during the latter part of pregnancy and during the first 2 years of life, there is a rapid accumulation of both DHA and ARA in the developing brain ¹⁴. Subsequent publications have shown that the DHA content of the infant brain is higher in breastfed infants compared with infants who receive infant formulas that are devoid of both DHA and ARA ^15,16. In addition, infants receiving a formula supplemented with added DHA and ARA have higher blood levels of DHA and ARA during the first year of life compared with infants who receive a formula that was not supplemented ¹⁷.

Human milk

In 2007, Brenna et al. published data from 65 studies and confirmed that DHA and ARA are consistently present in breast milk with the mean concentration of DHA being 0·32 percent fatty acids (range 0·06–1·4 percent) and the mean concentration of ARA was 0·47 percent (range 0·24–1·0  percent) ¹⁸.  In 2016, Fu et al. provided updated data from 78 studies conducted in 41 countries and included 4,163 breast milk samples and they reported that the worldwide mean levels of DHA and ARA in breast milk were 0·37 (SD 0·11) percent and 0·55 (SD 0·14) percent ¹⁹. Both studies showed that the ARA content of breast milk is more consistent compared with DHA, the latter being particularly influenced by maternal diet. The levels of DHA were remarkably low in populations with the greatest poverty with levels of 0·06 percent DHA in Pakistan, and Northern Sudan, and 0·10 percent DHA in Southern Sudan.

Based on the WHO recommendation on exclusive breastfeeding for 6 months and the assumption that the mother is receiving an adequate intake of DHA, infants will receive approximately 190 mg/d ARA and 130 mg/d DHA at 6 months. This is based on a breast milk intake of 850 ml/d and the reported mean concentrations of DHA and ARA in human milk. Breastfed infants should continue to receive a supply of DHA and ARA throughout the recommended breastfeeding period of 2 years or beyond. An infant exclusively receiving a formula without DHA and ARA will clearly have zero consumption from milk feeds during this time.

Complementary foods

From 6 months of age, breast milk or infant formula need to be complemented by higher energy food products that will meet the increasing energy and nutrient requirements of the rapidly growing infant.  There is clear evidence that in both developed and developing countries, the DHA and ARA content of complementary food intake is low ^20-23. In a global study, the contribution of DHA and ARA intake from complementary foods was directly related to the gross national income (GNI) of the country; the intakes of DHA and ARA from complementary foods during the period of 6-36 months for 76 medium- and low-income countries were 14.6 and 17.9 mg/day, respectively, and in the lowest income countries, intakes fell to 9.6 and 8.9 mg/day, respectively ²⁴. The DHA and ARA intake from complementary foods was exceptionally low in Nepal (DHA 0.7 mg/day; ARA 1.1 mg/day), Ethiopia (DHA 1.1 mg/day; ARA 3.8 mg/day), and Rwanda DHA 1.8 mg/day; ARA 1.7 mg/day). It is therefore evident that both breast milk and supplemented milk products, including infant formula, can provide a safety net for those infants at greatest risk of DHA and ARA deficiency during the first 3 years of life.

Endogenous synthesis

The importance of dietary intake of preformed DHA and ARA is highlighted by the evidence of low endogenous synthesis of these fatty acids during early life ²⁵. Endogenous synthesis of DHA and ARA is directed through a metabolic pathway where the n-3 and n-6 fatty acids compete for a shared desaturation and elongation enzyme system. As a consequence, the balance in intake of the essential 18-carbon n-3 and n-6 precursors can influence the levels of DHA and ARA derived from endogenous synthesis. The competition between n-3 and n-6 fatty acids is particularly evident at the rate-limiting Δ5- and Δ6-desaturase steps in the metabolic pathway.

It is now recognized that, in addition to substrate competition, the efficiency of the Δ-5 and Δ-6-desaturase steps are also dependent on the genotype of fatty acid desaturase 1 (FADS1) and desaturase 2 (FADS2), both located on chromosome 11, and which encode Δ-5 and Δ-6 desaturase enzymes, respectively ²⁶. Several studies have reported associations between single nucleotide polymorphisms (SNPs) in the FADS genes and LCPUFA status, with carriers of the minor alleles of FADS SNPs being associated with lower red blood cell content (RBC) of LCPUFAs, most notably of ARA, and it has been concluded that infant FADS genotype could contribute to differences in AA and DHA concentrations between breastfed and formula fed infants ²⁷.  Moreover, there is emerging data that there is regional and intra-regional variation in the prevalence of the minor alleles of FADS SNPs and this may contribute to population differences in LCPUFA status and subsequent health outcomes ^28,29. These data provide further evidence of the need to ensure that dietary intakes are sufficient to achieve optimum DHA and ARA status during early life.   

Because of the shared metabolic pathway, there is also a biochemical interdependence between DHA and ARA that needs to be considered when supplementing DHA and ARA. There is clear evidence from animal and human studies that alteration of the intake of either DHA or ARA can influence the endogenous synthesis of the other interdependent fatty acid and this can impact on brain composition. Non-human primate data revealed that DHA >ARA intake resulted in reductions in ARA concentrations in multiple areas of the brain ^30,31. More recently differences in human brain structure and function were reported in infants supplemented for the first 12 months of life with formula containing 0.64 percent of ARA and a range of DHA levels of 0.32 percent, 0.64 percent and 0.96 percent ³². Using magnetic resonance imaging (MRI) at age 9 years, differences in brain structure were found when the ratio of DHA to ARA significantly deviated from that present in breast milk, with the changes most evident in the anterior cingulate cortex, which controls attention and inhibition. This imaging data supported previous cognitive function data from this research cohort that showed attention control was diminished in infants who received a formula that had a higher DHA to ARA ratio compared to the mean ratio reported in breast milk ³³.

It is therefore evident that with low conversion rates from 18-carbon to 20- and 22-carbon fatty acids in early life, and DHA status being influenced by genetic variation in fatty acid metabolism, and an imbalance in dietary DHA and ARA intake altering DHA and ARA function ²⁵, a pragmatic way forward is to be guided by the composition of breast milk and supplement milk products in early life with levels of DHA and ARA that are equivalent to that reported in breast milk.  It has been recommended that at least 100 mg DHA per day, should be recognized as dietary reference values for infants 0-12 months of age ^7,34 and a scientific review concluded that an adequate daily intake of ARA during infancy is 140 mg per day.

Risk assessment

It is important that policymakers turn to risk assessors to discuss and consider the totality of the available evidence. Experimental data have demonstrated that n-3 LCPUFAs influence cellular membrane structure and function ^3,4,5,6, and DHA is especially important in the development of the brain and retina. DHA is also the precursor of potent lipid mediators called resolvins and protectins, that play crucial roles in the prevention or treatment of common chronic diseases that can cause significant morbidity and mortality. The n-6 LCPUFAs, particularly ARA, are widely distributed throughout human cells and tissues ⁶. In addition to the central nervous system where ARA plays an essential structural and functional role ³⁵, ARA is also a metabolic requirement for all cells as a precursor for eicosanoids which modulate a variety of biological processes, particularly those relating to cerebral, cardiovascular and immune function ⁶.

Translating the experimental evidence into clinical benefit has been challenging. This predominantly relates to difficulties with conducting intervention randomized controlled trials (RCTs) in infants and young children and the published RCTs show considerable variation in design, sample size and methodology; and they have mostly been undertaken in high-income countries ^36,37. The interventions have been limited to relatively short intervention periods, for example, the last 4-5 months of pregnancy or the initial months of the postnatal period. In the vast majority of studies, the intervention has included both DHA and ARA; there are only a handful of DHA alone studies and no published studies of ARA as the sole intervention. The majority of studies have used developmental assessments that provide an overall score for a wide range of cognitive functions. Based on this heterogeneous dataset some systematic reviewers have tended to conclude that the overall RCT data does not conclusively support or refute benefits from postnatal supplementation of DHA and ARA in preterm and term infants ³⁸, However, it is evident that many of the assessments adopted may not be sufficiently sensitive to specific areas of cerebral function and there are studies where a primary outcome has been specifically targeted, such as  visual function, problems solving, information processing and attention control, and the results from these studies are more consistent with positive effects in visual function and high-level cognitive functions ^39-43.

Conclusions

Relating early life nutritional interventions to later life health outcomes is always going to be challenging and all research methods will have their limitations. There is a real concern that null RCT studies of LCPUFA supplementations that have methodological weaknesses could outweigh the considerable evidence provided by experimental, animal and more specific visual and cognitive function studies. Population based evidence indicates that a high proportion of the global childhood population may be at risk of LCPUFA deficiency, especially in early life ²⁴ and it is important that the body of research available to policymakers reflects the diversity of need across communities and countries.

Infant formulas and follow-on formulas with both DHA and ARA have been consumed by more than 230 million infants worldwide over the last two decades and no national or international regulatory body has raised concerns regarding safety. The principal objective of recommendations on dietary DHA and ARA in early life should be to provide a safety net for the most vulnerable infants worldwide. Based on the well documented levels of DHA and ARA present in breast milk, and the WHO recommendation that breastfeeding should continue for 2 years or beyond, it is recommended that infants who are not breastfed should receive infant formulas and follow-on formulas that are supplemented with both DHA and ARA and in concentrations that are similar to breast milk (44,45). For countries that can clearly evidence that infants and young children consume adequate intakes of DHA and ARA during early life, an optional recommendation for these countries may be considered.

Engage with NUTRI-FACTS and its experts on LinkedIn.

1. Burr GO, Burr MM. A new deficiency disease produced by the rigid exclusion of fat from the diet J. Biol. Chem 1929; 82: 345–367.
2. Burr GO, Burr MM. On the Nature and Role of the Fatty Acids Essential in Nutrition J. Biol. Chem 1930; 6: 587–62.
3. Swanson D, Block R, Mousa SA: Omega-3 fatty acids EPA and DHA: Health benefits throughout life. Adv Nutr 2012; 3:1–7.
4. Abedi E, Sahari ME: Long-chain polyunsaturated fatty acid sources and evaluation of their nutritional and functional properties. Food Science and Nutrition 2014; 2: 443-463.
5. Calder PC. Functional roles of fatty acids and their effects on human health . J Parenter Enteral Nutr 2015; 39, Suppl.1, 18S-32S.
6. Hadley KB, Ryan AS, Forsyth S, Gautier S, Salem N Jr. The Essentiality of Arachidonic Acid in Infant Development. Nutrients 2016; 8, 216.
7. Food and Agriculture Organization of the United Nations. Fats and fatty acids in human nutrition. Report of an expert consultation. 10 − 14 November 2008, Geneva. FAO Food and Nutrition Paper 91. ISBN 978-92-5-106733-8. Rome, 2010. http://www.fao.org/docrep/013/i1953e/i1953e00.pdf
8. Crawford MA, Wang Y, Forsyth S, Brenna JT: The European Food Safety Authority recommendation for polyunsaturated composition of infant formula, overrules breast milk, puts infants at risk, and should be revised. Prostaglandins Leukot Essent Fatty Acids 2015; 102-103:1-3.
9. Markiewicz-Kęszycka M, Czyżak-Runowska G, Lipińska P et al. Fatty acid profile of milk - A review. Bull Vet Inst Pulawy 2013;57:135-139.
10. Dutta-Roy AK. Transport mechanisms for long-chain polyunsaturated fatty acids in the human placenta. Am J Clin Nutr. 2000;71:315S.
11. Herrera E. Implication of dietary fatty acids during pregnancy on placental, fetal and postnatal development—A review. Placenta. 2002;23: S9–S19. 
12. Fidler N, Sauerwald T, Pohl A, Demmelmair H, Koletzko B. Docosahexaenoic acid transfer into human milk after dietary supplementation: a randomized clinical trial. J Lipid Res. 2000;41:1376.
13. Richard C, Lewis ED, Field CJ. Evidence for the essentiality of arachidonic and docosahexaenoic acid in the postnatal maternal and infant diet for the development of the infant’s immune system early in life. Appl Physiol Nutr Metab 2016; 41: 461–475.
14. Martinez M. Tissue levels of polyunsaturated fatty acids during early human development. J Pediatr 1992; 120, S129-38.
15. Makrides M, Neumann Byard RW, Simmer K et al. Fatty acid composition of brain, retina, and erythrocytes in breast- and formula-fed infants. Am J Clin Nutr 1994;60: 89-94.
16. Farquharson J, Jamieson EC, Abbasi KA et al.  Effect of diet on the fatty acid composition of the major phospholipids of infant cerebral cortex. Arch Dis Child 1995; 72, 198-203.
17. Birch EE, Hoffman DR, Castaneda YS, Fawcett SL, Birch DG, Uauy RD. A randomized controlled trial of long-chain polyunsaturated fatty acid supplementation of formula in term infants after weaning at 6 wk of age. Am J Clin Nu 2002; 75 :70-580.
18. Brenna JT, Varamini B, Jensen, DA, Diersen-Schade DA, Boettcher JA, Arterburn LM. Docosahexaenoic and arachidonic acid concentrations in human breast milk worldwide. Am J Clin Nutr 85:1457–64, 2007.
19. Fu Y, Liu X, Zhou B, Jiang AC et al. An updated review of worldwide levels of docosahexaenoic and arachidonic acid in human breast milk by region. Public Health Nutr 2016; 19: 2675-87.
20. Sioen I, Huybrechts I, Verbeke W, Van Camp J, De Henauw S. n-6 and n-3 PUFA intakes of pre-school children in Flanders, Belgium. Br J Nutr 2007;98:819–825.
21. Sioen I, van Lieshout L, Eilander A, Fleith M, Lohner S, Szommer A, Petisca C, Eussen S, Forsyth S, Calder PC, Campoy C, Mensink RP. Systematic Review on N-3 and N-6 polyunsaturated fatty acid intake in European countries in light of the current recommendations - focus on specific population groups. Ann Nutr Metab. 2017; 70: 39-50.
22. Schwartz J, Dube K, Alexy U, Kalhoff H, Kersting M. PUFA and LC-PUFA intake during the first year of life: can dietary practice achieve a guideline diet? European Journal of Clinical Nutrition 2010; 64, 124–130.
23. Prentice AM, Paul AA. Fat and energy needs of children in developing countries. Am J Clin Nutr 2000 (suppl);72:1253S–65S.
24. Forsyth S, Gautier S, Salem N Jr. Estimated dietary intakes of arachidonic acid and docosahexaenoic acid in infants and young children living in developing countries. Ann Nutr Metab 2016; 69: 64-74.
25. Brenna JT. Arachidonic acid needed in infant formula when docosahexaenoic acid is present. Nutrition Reviews 2016; 74: 329-336.
26. Lattka E, Klopp N, Demmelmair H, Klinger JH, Koletzko B. Genetic Variations in Polyunsaturated Fatty Acid Metabolism – Implications for Child Health? Ann Nutr Metab 2012; 60 (Suppl 3): 8–17.
27. Salas Lorenzo I, Chisaguano Tonato AM, de la Garza Puentes A et al.  The Effect of an infant formula supplemented with AA and DHA on fatty acid levels of infants with different FADS genotypes: The COGNIS Study. Nutrients 2019; 11: 602; doi:10.3390/nu11030602.
28. Mathias R A, Sergeant S, Ruczinski I et al. The impact of FADS genetic variants on ω6 polyunsaturated fatty acid metabolism in African Americans. BMC Genetics 2011; 12: 50.
29. Miklavcic JJ, Larsen BMK, Mazurak VC et al. Reduction of arachidonate is associated with increase in B-cell activation marker in infants: A randomized trial. JPGN 2017;64: 446–453.
30. Hsieh AT, Anthony JC, Diersen-Schade DA, Rumsey SC, Lawrence P, Li C, Nathanielsz PW, Brenna JT. 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.
31. Hsieh AT, Brenna JT. Dietary docosahexaenoic acid but not arachidonic acid influences central nervous system fatty acid status in baboon neonates. Prostaglandins Leukot Essent Fatty Acids 2009; 81:105-10.
32. Lepping RJ, Honea RA, Martin LE, Liao K, Choi I-Y, Lee P, Papa, VB, Brooks WM, Shaddy DJ, Carlson SE, Colombo J, Gustafson KM (2019) Long‐chain polyunsaturated fatty acid supplementation in the first year of life affects brain function, structure, and metabolism at age nine years. Developmental Psychobiology 2019; 61: 5–16.
33. Colombo J, Jill Shaddy D, Kerling EH, Gustafson KM, Carlson SE. Docosahexaenoic acid (DHA) and arachidonic acid (ARA) balance in developmental outcomes.  2017; 121: 52-56.
34. European Food Safety Authority. EFSA Panel on Dietetic Products, Nutrition, and Allergies. Scientific Opinion on the essential composition of infant and follow-on formulae. EFSA Journal 2014; 12: 3760.
    
35. Harauma A, Yasuda H, Hatanaka E, Nakamura M, Salem N Jr, Moriguchi T, The essentiality of arachidonic acid in addition to docosahexaenoic acid for brain growth and function. Prostaglandins Leukot Essent Fatty Acids. 2017;116:9-18.
36. Meldrum SJ, Smith MA, Prescott SL, Hird K, Simmer K.  Achieving definitive results in long-chain polyunsaturated fatty acid supplementation trials of term infants: factors for consideration. Nutrition Reviews 69: 205–214, 2011.
37. Forsyth S. Why are we undertaking DHA supplementation studies in infants who are not DHA-deficient? Br J Nutr. 2012; 108: 948.
38. Jasani B, Simmer K, Patole SK, Rao SC. Long chain polyunsaturated fatty acid supplementation in infants born at term (Review). Cochrane Database of Systematic Reviews 2017, Issue 3. Art. No.: CD000376. DOI: 10.1002/14651858.CD000376.pub4.
39. Birch EE, Castañeda YS, Wheaton DH et al. (2005) Visual maturation of term infants fed long-chain polyunsaturated fatty acid-supplemented or control formula for 12 mo. Am J Clin Nutr 2005; 81, 871–879.
40. Colombo J, Carlson SE, Cheatham CL,et al. Long-chain polyunsaturated fatty acid supplementation in infancy reduces heart rate and positively affects distribution of attention. Pediatr Res 2011, 70:406-10.
41. Colombo J, Carlson SE, Cheatham CL, Shaddy DJ, Kerling EH, Thodosoff JM, Gustafson KM, Brez C. Long-term effects of LCPUFA supplementation on childhood cognitive outcomes. Am J Clin Nutr 2013; 98: 403-412.
42. Willatts P, Forsyth J, DiModugno M, Varma S, Colvin M. Effect of long-chain polyunsaturated fatty acids in infant formula on problem solving at 10 months of age. Lancet 1998; 352; 688-691.
43. Willatts P, Forsyth S, Agostoni C, Casaer P, Riva, E, Boehm, G. Effects of long-chain PUFA supplementation in infant formula on cognitive function in later childhood. Am J Clin Nutr 2013; 98  536S-542S.
    
44. Koletzko B, Carlson SC & van Goudoever JB Should infant formula provide both omega-3 DHA and omega-6 arachidonic acid? Ann Nutr Metab 2015; 66, 137–138.
45. World Health Organisation (WHO): Global strategy on infant and young child feeding. 2002.  http://www.who.int/nutrition/topics/infantfeeding_recommendation/en/.