Arachidonic acid (ARA, 20:4n-6) is an n-6 polyunsaturated 20-carbon fatty acid formed by the biosynthesis from linoleic acid (LA, 18:2n-6). This review considers the essential role that ARA plays in infant development. ARA is always present in human milk at a relatively fixed level and is accumulated in tissues throughout the body where it serves several important functions. Without the provision of preformed ARA in human milk or infant formula the growing infant cannot maintain ARA levels from synthetic pathways alone that are sufficient to meet metabolic demand. During late infancy and early childhood the amount of dietary ARA provided by solid foods is low. ARA serves as a precursor to leukotrienes, prostaglandins, and thromboxanes, collectively known as eicosanoids which are important for immunity and immune response. There is strong evidence based on animal and human studies that ARA is critical for infant growth, brain development, and health. These studies also demonstrate the importance of balancing the amounts of ARA and DHA as too much DHA may suppress the benefits provided by ARA. Both ARA and DHA have been added to infant formulas and follow-on formulas for more than two decades. The amounts and ratios of ARA and DHA needed in infant formula are discussed based on an in depth review of the available scientific evidence.
Dietary supplementation with DHA increases serum levels and, if given prior to traumatic brain injury, reduces the injury response, as measured by axonal injury counts, markers for cellular injury and apoptosis, and memory assessment by water maze testing. This uniform response was seen for the highest dosage group, 40 mg/kg given over 30 days prior to injury, but when measured by stereological counting methodology there was a positive response to anatomical injury across low to high doses of DHA. The potential for DHA to provide prophylactic benefit to the brain against traumatic injury appears promising and requires further investigation.
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