What Are the Three Essential Fatty Acids?

October 23, 2025 •

3 min read

The human body is unable to produce certain types of polyunsaturated fats, classifying them as essential fatty acids (EFAs) that must be obtained through diet. These vital nutrients play a critical role in cellular function, brain health, and inflammation regulation. Here, we explore what are the three essential fatty acids that are most crucial for human health.

Quick Summary

This guide details Alpha-linolenic acid (ALA), Eicosapentaenoic acid (EPA), and Docosahexaenoic acid (DHA), their distinct roles, and where to find these crucial nutrients to support overall wellness.

Key Points

ALA is the Plant-Based Omega-3: Alpha-linolenic acid (ALA) is the most common dietary omega-3, found in plant oils like flaxseed and canola, and serves as a precursor to other omega-3s.
EPA is Anti-Inflammatory: Eicosapentaenoic acid (EPA), derived from ALA or direct consumption, produces anti-inflammatory signaling molecules and is abundant in fatty fish.
DHA is Crucial for Brain and Eye Health: Docosahexaenoic acid (DHA) is a primary structural fat in the brain and retina and is especially important during development.
LA is an Essential Omega-6: Linoleic acid (LA) is also essential and is the parent of the omega-6 fatty acid family, found widely in many vegetable oils.
Balance is Key: Maintaining a healthy balance between omega-3 and omega-6 fatty acids is crucial for managing inflammatory responses and supporting overall health.
Limited Conversion from ALA: The body's conversion of ALA into the more biologically active EPA and DHA is inefficient, making direct intake of EPA and DHA highly beneficial.

The Three Main Essential Fatty Acids: ALA, EPA, and DHA

While Alpha-linolenic acid (ALA) and Linoleic acid (LA) are technically the only fatty acids the body cannot synthesize and are thus strictly “essential,” the term often includes Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA). This is because the body's ability to convert ALA into EPA and DHA is inefficient, making direct dietary intake important.

Alpha-Linolenic Acid (ALA)

ALA is an omega-3 fatty acid commonly found in the diet, serving as a precursor to other omega-3s. Primarily from plants, ALA is an energy source and part of cell membranes. Its structure, an 18-carbon chain with the first double bond at the third carbon from the methyl end, defines it as an omega-3.

Best sources of ALA:

Flaxseed and flaxseed oil
Chia seeds
Walnuts and walnut oil
Soybean and canola oil
Hemp seeds

Eicosapentaenoic Acid (EPA)

EPA is a longer, 20-carbon omega-3 derived from ALA. Direct consumption from marine sources is more efficient than the body's conversion of ALA. EPA is a precursor to eicosanoids, molecules that regulate functions and are known for their anti-inflammatory effects, contrasting with some omega-6 eicosanoids.

Best sources of EPA:

Fatty fish (salmon, mackerel, sardines, herring)
Fish oil supplements
Krill oil
Algal oil

Docosahexaenoic Acid (DHA)

DHA is a 22-carbon omega-3, also from ALA and concentrated in marine oils. It's a key structural element of cell membranes, especially in the brain and retina. DHA is the most abundant polyunsaturated fatty acid in these areas. It's crucial for visual and neurological development in infants.

Best sources of DHA:

Fatty fish (salmon, tuna)
Fish oil supplements
Krill oil
Algal oil
Some fortified eggs and dairy products

The Importance of Linoleic Acid (LA) - The Omega-6 EFA

Linoleic acid (LA) is also an essential omega-6 fatty acid and must be obtained through diet. LA is vital for skin, hair, bone health, and metabolism. However, the typical Western diet's high omega-6 to omega-3 ratio can promote inflammation. Thus, increasing omega-3 intake is often recommended.

Comparison of Essential Fatty Acids


Feature	Alpha-Linolenic Acid (ALA)	Linoleic Acid (LA)	Eicosapentaenoic Acid (EPA)	Docosahexaenoic Acid (DHA)
Classification	Omega-3 (Short-chain)	Omega-6 (Short-chain)	Omega-3 (Long-chain)	Omega-3 (Long-chain)
Essential Status	Truly essential; body cannot make	Truly essential; body cannot make	Conditionally essential; limited conversion from ALA	Conditionally essential; limited conversion from ALA
Primary Function	Energy source; precursor to EPA and DHA	Precursor to other omega-6s; supports skin, hair, and metabolism	Anti-inflammatory; precursor to potent eicosanoids	Key structural component of brain and retina
Key Food Sources	Flaxseed, walnuts, canola oil	Soybean oil, corn oil, sunflower oil, nuts	Fatty fish (salmon, sardines), fish oil, algal oil	Fatty fish, fish oil, algal oil, fortified foods
Body Conversion	Can be converted to EPA and DHA (inefficiently)	Can be converted to Arachidonic acid (AA)	Directly used; can be formed from ALA	Directly used; can be formed from ALA

Balancing Your Omega-3 and Omega-6 Intake

A healthy balance between omega-3 and omega-6 fatty acids is critical. While optimal ratios are debated, increasing omega-3 relative to omega-6 intake is generally considered beneficial. This involves consuming more marine and plant-based omega-3s and moderating high omega-6 intake from some vegetable oils.

Conclusion

Understanding what are the three essential fatty acids—ALA, EPA, and DHA—is key for health. The inefficient conversion of ALA to EPA and DHA highlights the importance of getting all three from the diet, especially through fatty fish, seeds, and nuts. A balanced intake of these fats supports heart health, brain function, and helps manage inflammation. For further reading, an authoritative source is the Linus Pauling Institute at Oregon State University.

Linus Pauling Institute Essential Fatty Acids

Frequently Asked Questions

Essential fatty acids, such as Alpha-linolenic acid (ALA) and Linoleic acid (LA), cannot be synthesized by the body and must be obtained from diet. Non-essential fatty acids can be produced by the body itself.

Although the body can convert ALA into EPA and DHA, the process is inefficient. For practical purposes, and to ensure adequate levels of these highly beneficial forms, dietary intake is considered essential.

For plant-based ALA, excellent sources include flaxseed, walnuts, and chia seeds. For marine-based EPA and DHA, good sources are fatty fish like salmon and mackerel, as well as fish oil and algal oil supplements.

Linoleic acid (LA) is found in many vegetable oils, including soybean, corn, and sunflower oils, as well as in nuts and seeds.

Yes, a balanced intake is crucial. The typical Western diet has a high ratio of omega-6 to omega-3, which can lead to increased inflammation. Many health experts recommend increasing omega-3 intake relative to omega-6.

While rare in developed countries, an essential fatty acid deficiency can lead to symptoms such as rough, scaly skin, dermatitis, and growth issues.

Yes. Vegetarians can obtain ALA from sources like flaxseed, walnuts, and chia seeds. For EPA and DHA, algal oil supplements are an effective vegetarian source.

Omega-3s, particularly EPA and DHA, are known to have anti-inflammatory effects and can help lower triglycerides, reduce blood pressure, and decrease the risk of heart disease.