Is ARA a fatty acid? Everything you need to know about Arachidonic Acid

December 27, 2025 •

2 min read

Arachidonic acid (ARA), or 20:4n-6, is a 20-carbon chain omega-6 polyunsaturated fatty acid and a fundamental component of cell membranes in the body. The question, "Is ARA a fatty acid?" has a clear scientific answer, but its implications for health, nutrition, and supplementation are complex and widely misunderstood.

Quick Summary

This article explains that Arachidonic Acid (ARA) is indeed an omega-6 polyunsaturated fatty acid essential for cell structure, signaling, and immune function. It covers dietary sources, metabolic pathways, and its crucial role in infant development and overall health.

Key Points

ARA is a fatty acid: Arachidonic Acid (ARA) is a specific type of omega-6 polyunsaturated fatty acid (PUFA), designated as 20:4(ω-6).
Building block for cell membranes: ARA is a crucial structural component of cell membranes throughout the body, particularly in the brain, liver, and muscles.
Precursor to signaling molecules: It is the main precursor for eicosanoids, powerful signaling molecules that regulate inflammation, immune response, and vascular tone.
Dietary sources: The body primarily obtains ARA from animal fats found in eggs, meat, poultry, and fish.
Important for infant development: Along with DHA, ARA is vital for the brain, eye, and nervous system development in infants, and is routinely added to infant formula.
Endogenous synthesis is limited: While the body can produce ARA from linoleic acid (an essential fatty acid), this process is slow and often insufficient to meet high demands, such as during infancy.
Balance with omega-3s is key: Maintaining a healthy balance between omega-6 (like ARA) and omega-3 (like DHA) fatty acids is important for regulating inflammatory processes.

Is ARA a Fatty Acid? The Definitive Answer

Yes, ARA (Arachidonic Acid) is unequivocally a fatty acid. It is a polyunsaturated omega-6 fatty acid with the biochemical shorthand 20:4(ω-6), indicating a 20-carbon chain and four double bonds, with the first double bond at the sixth carbon from the methyl end. This classification is fundamental to understanding its role in health.

The Importance of Arachidonic Acid

ARA is a crucial component of cell membranes, particularly in the brain, liver, and muscles, contributing to fluidity and flexibility essential for cell function. It is also the main precursor for eicosanoids, signaling molecules involved in various physiological processes. These include:

Inflammation regulation: Eicosanoids from ARA help mediate the body's inflammatory response.
Cardiovascular health: ARA metabolites affect blood circulation.
Immune function: ARA supports a healthy immune system.
Neurodevelopment: ARA is vital for brain growth in infants and cognitive function throughout life.

Where Do We Get Arachidonic Acid?

The body can make ARA from linoleic acid (LA), but this process is slow, making dietary sources important.

Animal Sources: Since animals synthesize ARA, it's found in chicken, eggs, beef, pork, and certain fish.
Microbial Sources: For supplements and infant formula, ARA is often derived from microorganisms like the fungus Mortierella alpina.

ARA vs. DHA: A Critical Balance

ARA (omega-6) and DHA (omega-3) are both vital for development, especially in infants. Experts recommend including both in infant formula to mirror breast milk composition. An imbalance can negatively impact development.


Feature	Arachidonic Acid (ARA)	Docosahexaenoic Acid (DHA)
Type	Omega-6 Polyunsaturated Fatty Acid (PUFA)	Omega-3 Polyunsaturated Fatty Acid (PUFA)
Key Functions	Immune response, muscle growth and repair, cell membrane structure, precursor to prostaglandins	Brain and eye development, cognitive function, nerve cell health
Dietary Sources	Primarily animal products (meat, eggs), some microbial sources	Primarily oily fish and some algae
Infant Needs	Supports brain and nervous system, and immune function. Should be provided alongside DHA in formula.	Crucial for rapid brain and retinal development. Often mandatory in infant formula.
Balance with Other FAs	High ARA intake without sufficient omega-3s can lead to a pro-inflammatory state; a balanced ratio is beneficial.	Proper balance with ARA is important, as high DHA levels can deplete ARA concentrations.

The Role of ARA in Infant Nutrition

Because infants have limited ability to synthesize ARA, dietary intake or supplementation is essential for their developing brains. Infant formulas are typically fortified with both DHA and ARA to provide complete nutrition similar to breast milk and support better neurodevelopmental outcomes.

Conclusion

ARA is a vital omega-6 polyunsaturated fatty acid. It's a key component of cell membranes and a precursor to signaling molecules involved in inflammation, immunity, and neurodevelopment. While the body can synthesize it, dietary sources like animal products are important. Maintaining a balance with DHA is critical for infant growth and health. Understanding ARA's role highlights the importance of balanced fatty acid intake. For more in-depth information, you can find extensive scientific literature on this topic through the National Institutes of Health (NIH) PubMed Central archive.

Frequently Asked Questions

ARA is an omega-6 fatty acid that primarily supports immune function, inflammation regulation, and muscle growth. DHA is an omega-3 fatty acid crucial for brain and eye development. Both are critical for infants and are found together in breast milk.

ARA is essential for health and is involved in numerous critical biological functions, including immune response and brain development. However, an imbalance with excessive omega-6 intake relative to omega-3s is sometimes associated with a pro-inflammatory state. The key is balance, not eliminating ARA.

Yes, the body can synthesize Arachidonic Acid from linoleic acid, an essential omega-6 fatty acid obtained from the diet. However, this conversion process is inefficient and often insufficient, especially in infants.

Arachidonic acid is found predominantly in animal products. Excellent dietary sources include chicken, eggs, beef, pork, and certain types of fish.

ARA is added to infant formula to provide a nutritional profile that more closely resembles breast milk. Infants have a limited ability to synthesize ARA, making dietary intake essential for proper brain, eye, and immune system development.

Eicosanoids are powerful, hormone-like signaling molecules derived from ARA. They play a wide range of roles throughout the body, including mediating inflammatory responses, regulating vascular tone, and influencing immune function.

A severe deficiency of ARA is rare in adults with a balanced diet. However, in infants, insufficient intake can negatively impact growth and immune and neurodevelopment.