What are the essential fatty acids not produced by humans?

December 23, 2025 •

3 min read

Studies show that while the human body can create most fats, it cannot synthesize all of them from scratch. These crucial nutrients, known as the essential fatty acids not produced by humans, must be obtained exclusively through diet to support vital bodily functions.

Quick Summary

An overview of the essential fatty acids, linoleic acid (LA) and alpha-linolenic acid (ALA), that must be consumed through diet to support critical bodily functions, including cellular and brain health.

Key Points

Two Core EFAs: Linoleic Acid (omega-6) and Alpha-Linolenic Acid (omega-3) are the only two fatty acids humans cannot produce.
Dietary Source: These essential fatty acids must be obtained entirely from food, as the human body lacks the necessary enzymes for their synthesis.
Vital Functions: EFAs are crucial for cell membrane structure, brain function, hormone production, and inflammation regulation.
Conversion to LC-PUFAs: While ALA and LA can be converted into longer-chain fatty acids like EPA and DHA, this process is inefficient, necessitating dietary intake of these derivatives as well.
Balanced Ratio: Maintaining a healthy balance between omega-6 and omega-3 fatty acids is important for health and to avoid pro-inflammatory states.
Deficiency Symptoms: A lack of EFAs can manifest in physical signs like dry skin and hair, as well as cognitive and mood changes.

What Makes a Fatty Acid 'Essential'?

Not all fats are created equal, and some are absolutely vital for survival. The term 'essential' in nutrition refers to a compound that the body cannot synthesize on its own and must therefore acquire from food. Humans cannot synthesize these essential fatty acids due to a lack of specific enzymes needed to create double bonds at certain positions. The two parent essential fatty acids are linoleic acid and alpha-linolenic acid.

The Two Essential Fatty Acid Families

Essential fatty acids belong to two families based on the location of the first double bond: Omega-6 (n-6) with Linoleic Acid (LA) as the parent, and Omega-3 (n-3) with Alpha-Linolenic Acid (ALA) as the parent. The body can make longer-chain fatty acids from these, but the process is often inefficient, making direct intake of derivatives like EPA and DHA important.

Linoleic Acid (LA): The Omega-6 Essential Fatty Acid

Linoleic acid (LA) is an 18-carbon omega-6 fatty acid. It is used to produce other omega-6 fatty acids, including arachidonic acid (AA), which is involved in creating eicosanoids that play a role in immune function.

Dietary Sources of Linoleic Acid

Omega-6 fatty acids are abundant in Western diets. Sources include various vegetable oils, nuts, seeds, and products made with these oils.

Alpha-Linolenic Acid (ALA): The Omega-3 Essential Fatty Acid

Alpha-linolenic acid (ALA) is an 18-carbon omega-3 fatty acid. It is often less common in modern diets than omega-6. While ALA can be converted to longer-chain omega-3s like EPA and DHA, the conversion is limited, particularly for DHA.

Dietary Sources of Alpha-Linolenic Acid

Good sources of ALA include flaxseeds, chia seeds, walnuts, and soybeans. Fatty fish and algal oil are direct sources of EPA and DHA.

The Importance of a Balanced Ratio

The balance between omega-3 and omega-6 intake is crucial, with many diets having an unfavorable high omega-6 to omega-3 ratio. A better balance supports anti-inflammatory processes and overall health.

Comparison Table: Omega-3 vs. Omega-6


Feature	Omega-3 (Alpha-Linolenic Acid)	Omega-6 (Linoleic Acid)
Classification	Essential Fatty Acid	Essential Fatty Acid
Body Production	Cannot be synthesized by humans	Cannot be synthesized by humans
Key Functions	Anti-inflammatory, brain health, eye health, nervous system function, heart health	Cell membrane structure, hormone production, immune function, energy source
Derivatives	EPA, DHA	Arachidonic acid (AA), Gamma-linolenic acid (GLA)
Effect on Inflammation	Typically anti-inflammatory	Precursors to both pro-inflammatory and anti-inflammatory compounds
Common Sources	Flaxseeds, chia seeds, walnuts, fatty fish	Vegetable oils (corn, soy), nuts, seeds

Symptoms of Essential Fatty Acid Deficiency

Essential fatty acid deficiency, though severe cases are rare, can lead to symptoms. These may include skin issues like dryness and dermatitis, brittle hair and nails, immune system problems, hormonal imbalances, and cognitive changes. Omega-3s, especially DHA, are important for brain function, and deficiency can affect concentration and mood.

Conclusion

The essential fatty acids humans cannot produce are linoleic acid (omega-6) and alpha-linolenic acid (omega-3). They are vital for numerous bodily functions. Due to inefficient conversion of ALA to EPA and DHA, consuming sources of these longer-chain omega-3s is also recommended. A balanced diet incorporating various sources like seeds, nuts, and fish is key for optimal EFA intake. For more information, see {Link: Linus Pauling Institute https://lpi.oregonstate.edu/mic/other-nutrients/essential-fatty-acids}.

Frequently Asked Questions

The two essential fatty acids that the human body cannot produce are Linoleic Acid (LA), an omega-6 fatty acid, and Alpha-Linolenic Acid (ALA), an omega-3 fatty acid.

The human body lacks the necessary desaturase enzymes required to insert double bonds at the correct locations in the omega-3 and omega-6 fatty acid carbon chains.

An essential fatty acid deficiency can cause symptoms including dry, scaly skin, brittle hair, a weakened immune response, hormonal imbalances, and cognitive difficulties.

Excellent sources of omega-3 fatty acids include flaxseeds, chia seeds, walnuts, and fatty fish like salmon, mackerel, and sardines.

Omega-6 fatty acids are common in vegetable oils, such as corn, soybean, and sunflower oil, as well as nuts and seeds.

Yes, many modern diets contain a higher proportion of omega-6 fatty acids than omega-3, which can contribute to chronic inflammation and metabolic issues. A balanced ratio is important for health.

While the body can convert ALA into EPA and DHA, the process is highly inefficient. Therefore, it is often recommended to consume foods or supplements rich in EPA and DHA directly, making them essential from a practical dietary perspective.