What is the difference between DHA and ARA?

December 27, 2025 •

3 min read

DHA and ARA are two long-chain fatty acids that are vital for infant growth and development, playing significant and complementary roles in the body. While both are crucial for neural and visual development, DHA is an omega-3 acid, while ARA is an omega-6 acid, representing a fundamental distinction in their biochemical pathways and primary functions.

Quick Summary

DHA and ARA are distinct omega fatty acids essential for development, with DHA being omega-3 and ARA being omega-6. They both support brain and eye health, but ARA is also key for immunity and muscle growth. A balanced intake of both is crucial, particularly for infants, as they have complementary functions in cellular development and signaling.

Key Points

Fatty Acid Family: DHA is an omega-3 fatty acid, and ARA is an omega-6 fatty acid.
Primary Functions: DHA primarily supports brain structure and eye development, while ARA is crucial for immune function and cell signaling.
Structural vs. Signaling: DHA acts as a major structural component in neural membranes, whereas ARA is a precursor to vital signaling molecules called eicosanoids.
Dietary Sources: DHA is abundant in fatty fish and algae, while ARA is found in animal products like meat and eggs.
Importance of Balance: Optimal health, especially in infants, requires a proper balance of both DHA and ARA, as they work together synergistically.
Role in Infants: Both fatty acids are critical during the first two years of life, supporting rapid brain and eye growth.

Understanding the Omega Fatty Acids

Docosahexaenoic acid (DHA) and arachidonic acid (ARA) are polyunsaturated fatty acids (PUFAs), the building blocks of lipids (fats). They are particularly important during infancy and early childhood, as the brain and eyes experience rapid development. Both are found naturally in human breast milk and are added to most infant formulas to mimic its nutritional profile.

DHA is an omega-3 fatty acid, a family of 'healthy' fats known for their anti-inflammatory properties and critical role in neurological and visual development. It is a primary structural component of the brain's cerebral cortex and the retina of the eyes. In contrast, ARA is an omega-6 fatty acid, known for its role in supporting immunity, muscle growth, and regulating inflammatory responses. Instead of being inherently 'bad,' ARA plays a crucial and complementary role to DHA, helping to regulate the body's inflammatory signaling system.

The Functional Differences: A Deeper Look

While DHA and ARA are often mentioned together due to their combined importance in development, their specific functions within the body differ. DHA focuses on optimizing the structure and function of cells, especially in the nervous system and retina. Its presence in cell membranes promotes fluidity, which is essential for efficient communication between neurons. ARA, on the other hand, is a precursor to vital signaling molecules called eicosanoids, which are involved in immune responses and inflammation. This unique dual role in modulating inflammation is essential for defending the body against pathogens while also facilitating tissue repair.

Comparison Table: DHA vs. ARA


Feature	DHA (Docosahexaenoic Acid)	ARA (Arachidonic Acid)
Fatty Acid Family	Omega-3 (n-3)	Omega-6 (n-6)
Primary Role	Structural component of brain and eye cells, supports neural and visual development.	Precursor to signaling molecules (eicosanoids) involved in immunity and inflammatory responses.
Key Functions	Brain development (gray matter, synapse formation), visual acuity (retina), cognitive function.	Immune system function, muscle growth and repair, proper inflammatory response, cardiovascular health.
Typical Ratio (in breast milk)	Varies widely based on maternal diet.	Typically higher than DHA, more stable than DHA.
Primary Sources	Fatty fish (salmon, tuna), fish oil, microalgae.	Meats (chicken, beef), eggs.

The Importance of Balance: A Synergistic Partnership

Numerous studies highlight that both DHA and ARA are necessary for optimal infant development, and a proper balance between the two is crucial. In fact, some research has indicated that higher levels of DHA without sufficient ARA may lead to suboptimal developmental outcomes. This is because these two fatty acids work synergistically to provide comprehensive nutritional support. For example, DHA is a primary structural component, while ARA provides the signaling and regulatory support for processes like cell growth and immune function.

Dietary Sources of DHA and ARA

For infants, the main source is either breast milk, where levels can be influenced by the mother's diet, or fortified infant formula. For older children and adults, diet becomes the primary means of intake. DHA is abundant in fatty fish like salmon, tuna, and anchovies, as well as fish oil and microalgae supplements. ARA is more common in animal products, including red meat, poultry, and eggs. Vegetarians and vegans may need to be mindful of their intake, as plant-based sources of the precursor fatty acids (like ALA) are inefficiently converted to DHA and ARA.

Conclusion: The Collaborative Duo for Optimal Health

While DHA and ARA are different classes of fatty acids—omega-3 and omega-6, respectively—they are a vital pair for early development and lifelong health. The key is not to favor one over the other, but to recognize their distinct yet complementary roles. DHA primarily builds and strengthens brain and eye structures, while ARA supports immunity, muscle function, and inflammatory modulation. This collaborative effect is essential for processes ranging from cellular communication to immune defense, underscoring why they are both standard ingredients in high-quality infant formulas and critical for a balanced diet throughout life. For further information on the broader roles of fatty acids, see the Journal of Pediatrics.

Frequently Asked Questions

DHA and ARA are vital for babies because their brains and eyes develop most rapidly during the first two years of life. DHA helps build and support brain and retinal cell membranes, while ARA assists with neural growth, immunity, and muscle tissue repair.

For adults, a balanced diet including fatty fish (for DHA) and meats/eggs (for ARA) is sufficient. However, infants rely on breast milk or fortified formula, and many toddlers may not get enough from weaning foods alone.

No, this is a common misconception. While an imbalanced ratio of omega-6 to omega-3 can be an issue, ARA plays a critical role in immune response, muscle growth, and inflammatory regulation. It is a necessary fatty acid that works in concert with DHA.

DHA is a major structural component of the brain's gray matter and retina. It is crucial for synaptogenesis (formation of synapses), neurotransmission, and maintaining the fluidity of cell membranes, which all support learning and memory.

ARA is a precursor to eicosanoids, powerful signaling molecules that help modulate inflammation and immune responses. These are essential for fighting infections, repairing tissue, and maintaining a healthy inflammatory balance.

The optimal ratio is still under study, but breast milk naturally contains a higher amount of ARA than DHA. Some experts recommend that infant formula contain at least as much ARA as DHA, as supplementing with high DHA levels alone may not be as beneficial as providing both.

Yes, DHA and ARA supplements are widely available, especially for infants in drop form, and for adults. Algae-based DHA is also available for vegetarians and vegans.