What are the 3 polyunsaturated fatty acids? The essential guide

November 2, 2025 •

3 min read

According to the American Heart Association, replacing saturated and trans fats with unsaturated fats, particularly polyunsaturated ones, can lower the risk of heart disease. Key to this dietary shift are three primary polyunsaturated fatty acids (PUFAs): alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

Quick Summary

Polyunsaturated fatty acids are essential fats obtained through diet, as the body cannot produce them. This guide details the three main types—ALA, EPA, and DHA—their functions, dietary sources, and importance for overall health.

Key Points

The three primary polyunsaturated fatty acids are ALA, EPA, and DHA: These are essential fats crucial for heart and brain health that the body cannot produce on its own.
ALA is plant-based and less efficient: Alpha-linolenic acid (ALA) is found in plant oils like flaxseed and is the precursor to EPA and DHA, though its conversion is poor.
EPA and DHA are mainly marine-sourced: Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are primarily found in fatty fish and algae.
Omega-3s are anti-inflammatory: EPA produces anti-inflammatory compounds, which is vital for managing chronic inflammation.
DHA supports brain health: DHA is a major structural component of the brain and eyes, crucial for cognitive development and function.
Balance between omega-3 and omega-6 is key: A healthy ratio of anti-inflammatory omega-3s to pro-inflammatory omega-6s is important for preventing chronic disease.

What are the 3 polyunsaturated fatty acids?

Polyunsaturated fatty acids (PUFAs) are essential fats, meaning the body cannot produce them and they must be obtained through food. They are characterized by having more than one double bond in their chemical structure. PUFAs belong to two main families: omega-3 and omega-6. Among the many types, the three most significant omega-3 polyunsaturated fatty acids for human health are Alpha-Linolenic Acid (ALA), Eicosapentaenoic Acid (EPA), and Docosahexaenoic Acid (DHA). These play vital roles in processes like brain, heart, and cellular function.

The omega-3 family: ALA, EPA, and DHA

Alpha-Linolenic Acid (ALA)

ALA is a common omega-3 found in plant-based foods and is considered the 'parent' omega-3. While the body can convert it to EPA and DHA, this process is inefficient. The body primarily uses ALA for energy. Good sources include flaxseeds, chia seeds, walnuts, and certain vegetable oils.

Eicosapentaenoic Acid (EPA)

EPA is a long-chain omega-3 primarily found in fatty fish. It is important for cell signaling and producing anti-inflammatory compounds called eicosanoids. EPA helps reduce inflammation and may assist in managing depression symptoms. Sources include salmon, mackerel, sardines, and marine algal oil.

Docosahexaenoic Acid (DHA)

DHA is crucial for brain and retinal health and is a significant structural component of the brain. It is vital for infant brain development and maintaining cognitive function. DHA promotes brain function and is essential for vision. Fatty fish and algal oil are rich sources.

The importance of the omega-6 balance

Omega-6 PUFAs are also essential. Linoleic acid (LA), common in vegetable oils, nuts, and seeds, is the main type. LA is converted to arachidonic acid (AA), which can produce pro-inflammatory eicosanoids. While some inflammation is necessary, an imbalance with too many omega-6s relative to omega-3s can lead to chronic inflammation linked to disease. A balanced intake of both is important.

Health benefits of polyunsaturated fatty acids

Replacing saturated and trans fats with PUFAs offers significant health benefits.

Cardiovascular health

PUFAs can improve cholesterol levels by lowering LDL and triglycerides, help regulate blood pressure, and reduce the risk of irregular heartbeats.

Brain and mental health

DHA supports cognitive function and development, potentially protecting against age-related decline. EPA may help manage depression. Omega-3s are essential for fetal brain development.

Anti-inflammatory effects

Omega-3s are anti-inflammatory, aiding in managing conditions like rheumatoid arthritis. A balanced intake supports a healthy immune system.

A comparison of omega-3 and omega-6 fatty acids


Feature	Omega-3 Fatty Acids	Omega-6 Fatty Acids
Primary Types	Alpha-linolenic acid (ALA), Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA)	Linoleic acid (LA), Arachidonic acid (AA)
Origin	Mainly marine (fish, algae for EPA/DHA) and some plant sources (ALA)	Mainly plant-based oils and seeds
Metabolic Precursors	ALA is the precursor for EPA and DHA.	LA is the precursor for AA.
Inflammatory Effect	Generally anti-inflammatory.	Can be pro-inflammatory if consumed in excess relative to omega-3s.
Key Functions	Brain and eye development, cognitive function, heart health.	Provides energy and is important for cell growth.

How to get enough polyunsaturated fats in your diet

Incorporate PUFAs by choosing whole-food sources and moderating omega-6 rich processed foods.

Include fatty fish: Eat two servings weekly of fish like salmon or sardines for EPA and DHA.
Use omega-3 rich oils: Cook with or use flaxseed, canola, or soybean oils in dressings.
Snack on nuts and seeds: Walnuts, chia, and flaxseeds provide ALA.
Choose healthy vegetable oils: Oils like avocado oil contain a mix of beneficial fats.
Consider algal oil for vegans/vegetarians: This provides direct EPA and DHA sources.

Conclusion

Understanding what are the 3 polyunsaturated fatty acids—ALA, EPA, and DHA—is key to a healthy diet. These essential fats, obtained from food, significantly benefit cardiovascular health, brain function, and inflammation management. By prioritizing omega-3 sources like fatty fish, seeds, and nuts while balancing omega-6 intake, you can leverage PUFAs for better health. For detailed guidance, consult resources like the National Institutes of Health.

Frequently Asked Questions

A polyunsaturated fatty acid (PUFA) is a type of fat molecule with more than one double bond in its chemical structure. The human body cannot create these fatty acids, so they must be obtained through diet and are considered essential nutrients.

Omega-3 and omega-6 are the two main types of PUFAs, differing in the location of their final double bond. Omega-3s (like ALA, EPA, DHA) are generally anti-inflammatory, while omega-6s (like linoleic acid) can be pro-inflammatory, especially when the intake ratio is unbalanced.

Docosahexaenoic acid (DHA) is the most critical PUFA for brain health. It is a major structural component of the brain and is vital for proper brain development and cognitive function.

While ALA is essential, it is less biologically active than EPA and DHA. The body can convert ALA into EPA and DHA, but the process is highly inefficient, meaning ALA intake alone is not enough to meet the body's needs for the longer-chain omega-3s.

The best dietary sources of EPA and DHA are fatty, oily fish such as salmon, mackerel, and sardines. For vegans and vegetarians, marine algal oil is an excellent source.

An imbalanced ratio, often with excessive omega-6 intake relative to omega-3s in modern Western diets, can lead to increased chronic inflammation. This condition is linked to a higher risk of heart disease and other chronic illnesses.

For those who do not consume enough fatty fish or plant-based sources, supplements like fish oil or algal oil can be beneficial to ensure adequate intake of EPA and DHA. The American Heart Association recommends supplements for individuals with existing heart disease.