ARA is the quieter half of the DHA and ARA pair in infant formula. Where DHA gets most of the attention because of its retinal and cerebral concentration, ARA is the major omega-6 long-chain polyunsaturated fatty acid in breast milk, and it serves as the building block for signaling molecules that govern immune response, inflammation, and neural membrane composition. The regulatory position is simple: if a formula has DHA, it should have at least as much ARA. EU law requires this. US law does not, though in practice most US brands include ARA.
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What ARA does
Arachidonic acid (ARA) is a 20-carbon omega-6 polyunsaturated fatty acid. It lives in the phospholipid membranes of most cells in the body, especially in the brain, retina, and immune-system cells. When cells need to generate signaling molecules (prostaglandins, thromboxanes, leukotrienes), they cleave ARA from the membrane as the substrate.
For a developing infant this matters in three ways:
- Neural membrane composition. ARA and DHA together account for a substantial share of the fatty acids in neural phospholipids. Membrane fluidity and signal transduction depend on the right balance.
- Immune signaling. The prostaglandins and leukotrienes derived from ARA are central to the immune response, inflammation modulation, pathogen defense, wound healing. Infant immune systems are developing rapidly during the first year and depend on substrate availability.
- Growth regulation. ARA-derived signals influence cell proliferation and differentiation in multiple tissues.
Why ARA must be balanced against DHA
DHA and ARA compete for some of the same metabolic pathways. A formula with high DHA but low ARA can shift the ratio away from the breast milk baseline, and the EFSA scientific review cited in Regulation 2016/127 flagged this as a nutritional concern. The resolution in EU law is a specific ratio requirement.
From EU Commission Delegated Regulation 2016/127 Annex I: infant formula must provide arachidonic acid at a level not lower than the DHA content. In practice, breast milk contains roughly equal or slightly higher ARA than DHA, and compliant EU formulas mirror this, for example, HiPP Dutch Stage 1 shows 13.2 mg ARA per 100 ml alongside 13.2 mg DHA.
Why the US is different
US FDA regulation (21 CFR Part 107) permits both DHA and ARA as nutrient additions but does not mandate either. Most major US brands voluntarily include both at roughly equal levels, following the scientific consensus that the pair matters more than either alone. But the regulatory floor is permissive, not mandatory.
This means a US parent reading a label needs to verify the ARA content specifically rather than assume it. Our Infant Formula Atlas shows the ARA content per 100 ml for every documented SKU.
Sources of ARA
ARA in infant formula comes from two sources:
- Microbial fermentation, Mortierella alpina oil. This is the most common source across EU and US formulas. M. alpina is a soil fungus that produces a high-ARA oil suitable for food use. HiPP, Holle, and most major brands use this.
- Algal oil, Schizochytrium species. Less common for ARA specifically (algae are more established as DHA sources), but used in some vegan-positioned formulas.
The ARA molecule is the same regardless of source. Absorption is identical.
What the research says
The evidence base for ARA is thinner than for DHA because ARA has rarely been studied in isolation, almost every trial administers DHA and ARA together. What is documented:
- Formulas with both DHA and ARA at breast-milk-approximate levels produce infants whose fatty acid profiles match breastfed infants. Formulas with DHA alone do not.
- Immune-function markers (cytokine profiles, infection rates in some studies) appear better in DHA and ARA formulas than in DHA-only formulas, though effect sizes are modest and not universal across trials.
- No documented harm at the ratios permitted by EU regulation.
How to check ARA in any formula
The Infant Formula Atlas lists ARA content for every documented SKU. If a formula shows DHA but no ARA, the nutrition panel should be confirmed against the manufacturer label, sometimes ARA is provided but not separately declared because the regulation or labeling convention differs.
For parents comparing US and European options, the short rule is: if the formula has DHA, it should have at least as much ARA. Every compliant EU formula satisfies this. Most US formulas do too, voluntarily, but verify per SKU.
Frequently asked questions
What is ARA and why does formula contain it?
Why must ARA be paired with DHA?
Where does ARA in formula come from?
How much ARA should infant formula contain?
Do all US formulas include ARA?
Is ARA the same as 'omega-6' on the label?
Primary sources
- EU Commission Delegated Regulation 2016/127: Annex I specifies the ARA requirement relative to DHA. eur-lex.europa.eu
- Koletzko B et al. Should formula for infants provide arachidonic acid along with DHA? Journal of Pediatric Gastroenterology, 2020. pubmed.ncbi.nlm.nih.gov/32024829
- EFSA Panel on Dietetic Products. Scientific opinion on the essential composition of infant and follow-on formulae, EFSA Journal, 2014. efsa.europa.eu
- Hadley KB et al. The essentiality of arachidonic acid in infant development. Nutrients, 2016. pubmed.ncbi.nlm.nih.gov/30723218
Related reading
- Brands, comparisons featuring ARA, and DHA, HiPP brand hub (ARA and DHA across the Combiotik line), Bobbie brand hub (algal-sourced ARA and DHA), HiPP vs Bobbie (fish oil vs algal sourcing)
- EU Regulation 2016/127 overview
- FDA vs EFSA standards compared
This site provides research and comparisons, not medical advice. Consult your pediatrician before changing your baby's formula.