By: Lucy Jones, MRES BSC Hons RD MBDA
September 7, 2017
We often hear about good fats and bad fats but the truth is – most fats play an important role in our health when consumed in the right proportions. While many parents recognize the role of omega-3 fatty acids such as docosahexaenoic acid (DHA) for brain development in young children, far fewer recognize the role of omega-6 arachidonic acid (ARA). ARA is often a forgotten essential nutrient. For young children however, ARA is both a structural and metabolically active lipid1, playing an essential role in infant development.
ARA is the primary omega-6 fatty acid found in the brain and is a key part of cell membranes2.
ARA has very different functions than DHA3. While DHA plays a role in the development of our eyes, brain and nervous system, ARA is invaluable to our immunity and brain growth4.
In the past, pre-clinical studies demonstrated the importance of ARA for growth and maturation of brain nerves and controlling inflammation in various conditions. These studies also showed that both DHA and ARA are needed for optimal cognitive and neurological development5.
Both DHA and ARA are preferentially transferred to the baby across the placenta as well as in early infancy compared to other long-chain fatty acids6,7,8. After birth, breast-fed infants take in both DHA and ARA directly from breast milk, while formula-fed infants get DHA and ARA from supplemented formulas.
Infant formulas without ARA results in a dramatic decrease in a baby’s ARA status shortly after birth 3,9,10,11,12,13, especially in preterm babies who miss out on the third trimester’s maternal supply of ARA and DHA. In research studies, providing high amounts of DHA/EPA without providing ARA has been associated with adverse effects on growth in premature babies14,15,16,17. The most recent research shows that the cognitive benefit provided to babies from formulas supplemented with DHA starts to decrease at the highest doses. Looking at the babies’ blood has now shown that this highest level of supplemented DHA reduces the blood level of ARA, which could well be why the cognitive benefits drop18.
The combination of ARA and DHA has shown benefits for cognitive development, visual function, and blood pressure well beyond the period of supplementation and into early childhood 19,20,21. Therefore it is important that infants are breast fed as they will get these key nutrients via breast milk. In situations where infants cannot be breastfed, providing a formula supplemented with both DHA and ARA is key.
The composition of different fatty acids in human milk varies depending on the mother’s diet with a high intake of fish and seafood resulting in the highest breast milk content of DHA. In general, DHA concentrations vary the most of all the fatty acid concentrations in human milk, while the content of ARA is much more stable22. In developing countries, dietary intakes of ARA and DHA in early life (6-36m) are lower than current recommended levels because of low intakes of meat and fish.
The FAO/WHO 2010 publication concluded “There can be little doubt about the essentiality of DHA and ARA for the brain”23. According to this statement, DHA and ARA should be included in infant formula with DHA (from 0.2% to 0.5% of total fatty acids) and added ARA should be at least equal to the amount of DHA24. For more than 10 years, both DHA and ARA have been added to infant formulas worldwide in an attempt to match the nutrient supply and functional benefits achieved with human milk. The stability of the ARA level in human milk is biologically important because it provides preformed ARA consistently at a time when brain growth and development is most critical3. Although DHA is more variable than ARA it is always present in human milk and the balance between ARA and DHA can be as much as 2 to 1.
Clinical evidence to support the safe removal of ARA from infant formula and follow-on formula containing DHA is lacking1. In light of the universal presence of ARA in human milk and the essential ARA functions, all infant formulas should be matched as closely as possible to human breast milk in order to support the same growth and development in all babies with the right balance of both DHA and ARA.
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