How Many Fatty Acids Are There? A Comprehensive Guide

December 24, 2025 •

4 min read

More than 70 fatty acids have been identified in nature, with some sources suggesting over 100 different types exist in certain food products like butterfat. This immense variety means the answer to 'how many fatty acids are there?' is not a simple number, but a complex topic best understood through classification.

Quick Summary

The exact number of fatty acids is unknown and varies widely, with classification based on saturation, chain length, and omega position. Main categories include saturated, monounsaturated, and polyunsaturated fats.

Key Points

No Single Number: There is no definitive count for fatty acids, with hundreds of natural variants existing due to differences in chain length, saturation, and structure.
Classification is Key: Understanding the classifications of fatty acids—by saturation (saturated vs. unsaturated), chain length, and omega position—is more practical than trying to quantify them.
Saturated vs. Unsaturated: The presence or absence of double bonds determines a fatty acid's saturation level, which in turn influences its physical properties, like being solid (saturated) or liquid (unsaturated) at room temperature.
Essential vs. Non-essential: Humans must get essential fatty acids like linoleic and alpha-linolenic acid from their diet because the body cannot produce them on its own.
Diverse Health Effects: Different classes of fatty acids have varied effects on health, from potentially raising LDL cholesterol (saturated fats) to supporting heart and brain health (omega-3 polyunsaturated fats).

The Simple Answer: Why No Single Number Exists

There is no single, definitive number for how many fatty acids exist because of their vast diversity. They are fundamentally carboxylic acids with hydrocarbon chains, but the specific number is fluid and depends on how they are categorized. The variations come from differences in chain length, the number and position of double bonds, and their spatial orientation (cis or trans). For instance, a single food item like butterfat may contain over 100 different types of fatty acids, although many are only present in trace quantities. For this reason, it is more useful to understand the major classes and common examples rather than trying to memorize a specific number.

Classification by Saturation: Saturated vs. Unsaturated

One of the most common ways to classify fatty acids is by their level of saturation, which refers to the number of double bonds in their carbon chain. This structural difference profoundly affects their physical properties and biological function.

Saturated Fatty Acids (SFAs)

Saturated fatty acids contain no carbon-carbon double bonds, meaning their carbon backbone is fully "saturated" with hydrogen atoms. This straight, flexible structure allows them to pack tightly together, making them solid at room temperature. They are abundant in animal-based fats and certain plant oils.

Examples of SFAs:

Butyric acid (C4:0): Found in butterfat.
Palmitic acid (C16:0): Common in most fats and oils.
Stearic acid (C18:0): Also found in most fats and oils.

Unsaturated Fatty Acids

Unsaturated fatty acids, conversely, contain at least one double bond in their carbon chain. This double bond introduces a rigid bend or 'kink' in the chain (in the case of the more common cis configuration), preventing them from packing as densely and causing them to be liquid at room temperature. Unsaturated fatty acids are further divided into two subcategories.

Monounsaturated Fatty Acids (MUFAs)

MUFAs contain only one double bond in their carbon chain. A well-known example is oleic acid, which is abundant in olive oil.

Polyunsaturated Fatty Acids (PUFAs)

PUFAs contain two or more double bonds in their carbon chain. The human body cannot synthesize certain PUFAs, known as essential fatty acids, and they must be obtained from the diet.

Differentiating by Carbon Chain Length

Fatty acids can also be classified by the number of carbon atoms in their chain, which impacts how the body processes them.

Short-Chain Fatty Acids (SCFAs): Have fewer than 6 carbon atoms. Butyric acid (C4) is a common example.
Medium-Chain Fatty Acids (MCFAs): Contain 6 to 12 carbon atoms. Caprylic acid (C8) and capric acid (C10) are found in palm kernel and coconut oils.
Long-Chain Fatty Acids (LCFAs): Consist of 13 to 21 carbon atoms. Palmitic acid (C16) and oleic acid (C18) are very common LCFAs.
Very Long-Chain Fatty Acids (VLCFAs): Have more than 22 carbon atoms. Important VLCFAs include erucic acid (C22) and nervonic acid (C24).

The Omega System: Positional Naming for PUFAs

For polyunsaturated fatty acids, another important classification system is based on the position of the first double bond, counting from the methyl (omega) end of the carbon chain.

Omega-3 Fatty Acids: The first double bond is three carbons from the omega end. Key examples include alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
Omega-6 Fatty Acids: The first double bond is six carbons from the omega end. Linoleic acid (LA) is a primary omega-6 fatty acid.
Omega-9 Fatty Acids: While not essential like omega-3 and omega-6, these fatty acids have a double bond nine carbons from the omega end. Oleic acid is the most well-known omega-9 fatty acid.

Essential vs. Non-essential Fatty Acids

This classification is critical for human health. Essential fatty acids (EFAs) are those the human body cannot synthesize and must be obtained from the diet. The two primary EFAs are alpha-linolenic acid (an omega-3) and linoleic acid (an omega-6). George and Mildred Burr's pioneering work in 1929 established the concept of EFAs, demonstrating that their absence from a diet could cause deficiency diseases. While other fatty acids like EPA and DHA are important, they can be produced from ALA in the body, although the conversion is often limited, making dietary intake of these important. Non-essential fatty acids are those the body can produce on its own, such as omega-9 fatty acids. For more on the history of this important discovery, see this Frontiers article on fatty acids.

A Comparison of Fatty Acid Types


Feature	Saturated Fatty Acids (SFAs)	Monounsaturated Fatty Acids (MUFAs)	Polyunsaturated Fatty Acids (PUFAs)
Double Bonds	None	One	Two or more
State at Room Temp.	Solid	Liquid (but can thicken when chilled)	Liquid
Key Dietary Sources	Animal fats (meat, butter), dairy, coconut oil, palm oil	Plant oils (olive, canola, peanut), avocados, nuts	Plant oils (soybean, sunflower, corn), seeds (flax, walnuts), fatty fish
Health Effects	High intake may raise LDL ("bad") cholesterol; moderate intake is part of a balanced diet.	Can help lower LDL cholesterol and raise HDL ("good") cholesterol.	Can help lower LDL cholesterol and support cellular health; essential types must be consumed.
Shape	Straight chain	Contains a bend or 'kink' at the double bond	Multiple bends or 'kinks'

Conclusion: The Diverse World of Fatty Acids

Ultimately, the question of "how many fatty acids are there" is less important than understanding their fundamental characteristics and classifications. The number is constantly expanding as new variants are discovered in nature or created synthetically. The key takeaway for nutrition and biochemistry is to appreciate the wide spectrum of fatty acids—from short-chain to very long-chain, and from saturated to highly unsaturated—and to recognize the profound health implications of each type. Recognizing the different types and their roles, particularly the essential ones, is far more useful than an arbitrary number.

Frequently Asked Questions

A saturated fatty acid has no double bonds in its carbon chain, making it straight and solid at room temperature. An unsaturated fatty acid has at least one double bond, which introduces a 'kink' and makes it liquid at room temperature.

The three main types of fatty acids are saturated (no double bonds), monounsaturated (one double bond), and polyunsaturated (two or more double bonds).

Essential fatty acids (EFAs) are polyunsaturated fats that the human body cannot produce on its own. They are crucial for normal body function and must be obtained through diet. The two main EFAs are alpha-linolenic acid (ALA) and linoleic acid (LA).

Yes, omega-3 and omega-6 fatty acids are both polyunsaturated fatty acids (PUFAs), but they are differentiated by the position of the first double bond in their carbon chain. Omega-3 has the first double bond at the third carbon from the omega end, while omega-6 has it at the sixth.

Most naturally occurring fatty acids have an even number of carbon atoms, a consequence of how they are biosynthesized from two-carbon units. However, fatty acids with odd numbers of carbon atoms do exist, although they are less common.

Fatty acids serve as building blocks for lipids and cell membranes, act as energy storage molecules (as triglycerides), function as signaling molecules and hormones, and aid in the absorption of fat-soluble vitamins.

Fatty acids are found in a wide range of foods. Saturated fats are common in animal products like meat and dairy, while unsaturated fats are more prevalent in plant-based sources like vegetable oils, nuts, and seeds, as well as fatty fish.