What is the common name for the fatty acid 18:3 δ9,12,15?

January 4, 2026 •

2 min read

According to the National Institutes of Health, alpha-linolenic acid (ALA) is one of the three main omega-3 fatty acids vital for human health. It is a fundamental component of cell membranes and an essential nutrient that the body cannot produce on its own. This article delves into the common name and importance of the fatty acid specified by the scientific notation 18:3 δ9,12,15.

Quick Summary

The fatty acid 18:3 δ9,12,15 is most commonly known as alpha-linolenic acid, or ALA. An essential omega-3 fatty acid, ALA is required for normal bodily functions and must be obtained through dietary sources. It is a vital component for cellular health, energy, and the production of other crucial long-chain omega-3s.

Key Points

Common Name: The fatty acid 18:3 δ9,12,15 is commonly known as alpha-linolenic acid (ALA).
Omega-3 Classification: ALA is a type of omega-3 fatty acid because its first double bond is at the third carbon from the methyl end of the molecule.
Essential Nutrient: ALA is an essential fatty acid that the human body cannot produce and must be obtained through dietary intake.
Key Sources: Rich plant-based sources of ALA include flaxseed oil, chia seeds, walnuts, and canola oil.
Converted to EPA and DHA: The body can convert ALA into longer-chain omega-3s like EPA and DHA, although this process is inefficient.

Understanding Fatty Acid Nomenclature

Fatty acid nomenclature, like "18:3 δ9,12,15", provides structural details. "18:3" indicates 18 carbon atoms and 3 double bonds. The delta notation "δ9,12,15" specifies the double bond locations at the 9th, 12th, and 15th carbons from the carboxylic acid end.

This structure corresponds to alpha-linolenic acid (ALA). It is also classified as an omega-3 fatty acid because the first double bond is three carbons from the methyl (omega) end.

The Importance of ALA in Human Health

ALA is an essential fatty acid crucial for human health, particularly growth and development. The body cannot produce it, so dietary intake is necessary. ALA serves multiple roles:

Energy Source: Provides calories.
Cellular Structure: A key component of cell membranes.
Precursor: Can be converted into longer-chain omega-3s, EPA and DHA, although this process is inefficient.

Key Sources of Alpha-Linolenic Acid

ALA is abundant in plant foods. Rich sources include:

Flaxseeds and flaxseed oil
Chia seeds
Walnuts
Canola oil
Soybeans and soybean oil
Hemp seeds and oil

Omega-3 vs. Omega-6: Understanding the Balance

ALA is an omega-3, distinct from omega-6 fatty acids like linoleic acid (18:2 δ9,12). A balanced intake of omega-3s and omega-6s is vital, with a ratio of 1:1 to 4:1 often recommended. Many diets are too high in omega-6, and increasing ALA intake can help correct this imbalance.

Comparison of ALA and its Omega-3 Derivatives


Feature	Alpha-Linolenic Acid (ALA)	Eicosapentaenoic Acid (EPA)	Docosahexaenoic Acid (DHA)
Source	Plant-based (flaxseed, walnuts, chia seeds)	Primarily marine-based (fatty fish, algae oil)	Primarily marine-based (fatty fish, algae oil)
Classification	Short-chain omega-3 fatty acid	Long-chain omega-3 fatty acid	Long-chain omega-3 fatty acid
Conversion	Can be converted by the body into EPA and DHA, but conversion is limited.	Can be formed from ALA and is a precursor to DHA.	The longest-chain omega-3, formed from EPA.
Key Functions	Precursor to EPA and DHA, energy source, cellular structure.	Reduces inflammation and supports cardiovascular health.	Crucial for brain, retina, and nervous system development and function.

Conclusion: The Cornerstone of Omega-3s

The fatty acid 18:3 δ9,12,15 is commonly called alpha-linolenic acid (ALA). It's an essential omega-3 primarily found in plants. While it converts to EPA and DHA, this conversion is limited, underscoring the need for diverse omega-3 sources for optimal health. Incorporating ALA-rich foods supports a healthy fatty acid balance.

For more detailed information on essential fatty acids and their roles, the Linus Pauling Institute at Oregon State University provides comprehensive resources on nutrition(https://lpi.oregonstate.edu/mic/other-nutrients/essential-fatty-acids).

Frequently Asked Questions

Alpha-linolenic acid (ALA) is considered an essential fatty acid because the human body cannot synthesize it from other substances, meaning it must be obtained through the diet.

The main difference is their classification: ALA is an omega-3 fatty acid, while GLA is an omega-6 fatty acid. They are structural isomers, with ALA having its first double bond at the third carbon from the omega end, and GLA having its first at the sixth.

No, ALA cannot provide the same full range of benefits as EPA and DHA. While the body can convert some ALA to EPA and DHA, the conversion rate is very low, especially for DHA, making direct intake of EPA and DHA from food or supplements the most practical way to increase their levels.

While there is no single consensus, many experts suggest a ratio of omega-6 to omega-3 between 1:1 and 4:1 for optimal health. However, Western diets typically have a much higher ratio, and focus should be on increasing omega-3 intake rather than simply reducing omega-6.

ALA is generally safe when consumed in amounts found in food. However, it is high in calories, and excessive intake could potentially contribute to weight gain. As with any dietary change, it is best to consult a healthcare provider.

No. While most plant sources, like flaxseeds and walnuts, are rich in ALA, marine algae and seaweed are among the few plant-based sources that also contain EPA and DHA.

ALA is thought to decrease the risk of heart disease by helping to maintain normal heart rhythm, lowering triglyceride levels, and reducing blood clots. Some studies suggest higher ALA intake is associated with lower cardiovascular mortality.