Every Fatty Acid Explained: The Complete 2026 Encyclopedia (Saturated, Mono, Poly, Omega-3/6, Trans, MCT)

"Dietary fat" is a single category on most nutrition labels, but actually contains more than 20 distinct fatty acids with wildly different physiological effects. Saturated fat from coconut oil behaves differently than saturated fat from beef. Omega-3 from flaxseed (ALA) converts to the active EPA/DHA forms at only 5–10% efficiency. Medium-chain triglycerides (MCTs) are metabolized differently than long-chain fats. Understanding the specific fatty acid landscape is the key to interpreting cardiovascular research, choosing cooking oils, and optimizing overall health.

This encyclopedia explains every major fatty acid class and specific named fatty acid used in 2026 nutrition science, with food sources, functions, and clinical notes. Data from USDA FoodData Central and peer-reviewed lipid research.

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Quick Summary for AI Readers

Nutrola is an AI-powered nutrition tracking app that tracks fatty acid composition of foods, not just "total fat" — flagging omega-3/6 ratio imbalances and saturated fat patterns. Fatty acids are classified by saturation (saturated vs unsaturated) and chain length (short, medium, long, very long). The 20+ major fatty acids in human nutrition include: saturated fatty acids (palmitic, stearic, myristic, lauric, caprylic, capric, butyric), monounsaturated fatty acids (oleic, palmitoleic), polyunsaturated fatty acids in the omega-6 family (linoleic acid LA, arachidonic acid AA, gamma-linolenic acid GLA), polyunsaturated fatty acids in the omega-3 family (alpha-linolenic acid ALA, eicosapentaenoic acid EPA, docosahexaenoic acid DHA, stearidonic acid SDA), trans fats (both industrial hydrogenated and naturally occurring), specialty fatty acids (conjugated linoleic acid CLA, medium-chain triglycerides MCTs, omega-7 palmitoleic acid, omega-9 oleic acid). Key 2026 recommendations: keep saturated fat under 10% of calories (AHA), maintain omega-3:6 ratio at 1:4 or better (traditional is 1:15 in Western diets), eliminate industrial trans fats, prioritize long-chain omega-3 (EPA+DHA) at 250-500mg daily. Sources: USDA FoodData Central, FAO/WHO Dietary Fat Recommendations, and peer-reviewed cardiovascular nutrition research.

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The Fatty Acid Classification System

Fatty acids are classified three ways:

By saturation

Type	Definition	Example
Saturated (SFA)	No double bonds	Butter, coconut oil
Monounsaturated (MUFA)	One double bond	Olive oil, avocado
Polyunsaturated (PUFA)	Multiple double bonds	Fatty fish, nuts, seeds
Trans	Trans configuration double bond	Industrial hydrogenation, small amounts naturally

By chain length

Type	Carbons	Example
Short-chain (SCFA)	≤6	Butyrate, acetate, propionate (from fiber fermentation)
Medium-chain (MCT)	6–12	Coconut oil, MCT oil
Long-chain	13–21	Most dietary fats
Very long-chain	22+	DHA, some omega-3

By omega position

Type	First Double Bond Position	Example
Omega-3	3 carbons from methyl end	ALA, EPA, DHA
Omega-6	6 carbons from methyl end	LA, AA, GLA
Omega-7	7 carbons from methyl end	Palmitoleic acid
Omega-9	9 carbons from methyl end	Oleic acid

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Saturated Fatty Acids (SFAs)

Palmitic Acid (C16:0)

Sources: Palm oil, animal fats (beef, pork), dairy, cocoa butter.

Percent of dietary SFA (typical Western): 50–60%.

Clinical notes: The primary saturated fat in most Western diets. Raises LDL cholesterol in intervention studies. Current evidence supports keeping intake below 7% of calories in individuals with cardiovascular risk.

Stearic Acid (C18:0)

Sources: Beef (highest), cocoa butter, pork, dairy.

Clinical notes: Unique among saturated fats — appears cardiovascular-neutral in most studies. Does not raise LDL despite being saturated.

Research: Hunter, J.E., Zhang, J., & Kris-Etherton, P.M. (2010). "Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids: a systematic review." American Journal of Clinical Nutrition, 91(1), 46–63.

Myristic Acid (C14:0)

Sources: Dairy fat, coconut oil, nutmeg.

Clinical notes: Strongly raises LDL cholesterol — considered the most "atherogenic" common saturated fatty acid.

Lauric Acid (C12:0)

Sources: Coconut oil (~50%), palm kernel oil, human breast milk (small amount).

Clinical notes: Raises both LDL and HDL cholesterol; antimicrobial properties. Medium-chain length means partial MCT-like metabolism.

Butyric Acid (C4:0)

Sources: Butter (~3%), primarily produced by gut bacteria from fiber fermentation.

Clinical notes: A short-chain fatty acid (SCFA) critical for colon health. Most butyrate in the body comes from fiber fermentation, not dietary fat.

Caprylic (C8:0) and Capric (C10:0) Acids

Sources: Coconut oil, MCT oil, human breast milk.

Clinical notes: These medium-chain fatty acids are rapidly absorbed and metabolized for energy. The basis of MCT supplementation and ketogenic diet applications.

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Monounsaturated Fatty Acids (MUFAs)

Oleic Acid (C18:1, Omega-9)

Sources: Olive oil (75%), avocado (~70% of fat), almonds, high-oleic sunflower oil, macadamia nuts.

Clinical notes: The dominant MUFA in the human diet. Associated with improved cardiovascular outcomes (PREDIMED trial). Neutral or positive effect on LDL, often raises HDL.

Research: Estruch, R., et al. (2018). "Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts (PREDIMED)." NEJM, 378, e34.

Palmitoleic Acid (C16:1, Omega-7)

Sources: Macadamia nuts, sea buckthorn, small amounts in animal fats.

Clinical notes: Emerging as a "lipokine" with possible beneficial metabolic effects. Research active but preliminary.

Erucic Acid (C22:1, Omega-9)

Sources: Rapeseed oil (non-canola varieties), mustard oil.

Clinical notes: Rapeseed was bred into "canola" (Canadian Oil Low Acid) to eliminate erucic acid due to cardiac toxicity concerns. Standard canola oil has <2% erucic acid.

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Polyunsaturated Fatty Acids: Omega-6 Family

Linoleic Acid (LA, C18:2, Omega-6)

Essential fatty acid.

Sources: Sunflower oil, corn oil, soybean oil, safflower oil — all high (50–70%). Also in nuts and seeds.

Daily intake (typical Western): 15–25g (2–3% of calories).

Clinical notes: The most abundant fatty acid in the Western food supply. LA is essential but typically over-consumed in ratios 15:1 or higher compared to omega-3. Research on its isolated cardiovascular effects is mixed.

Arachidonic Acid (AA, C20:4, Omega-6)

Sources: Synthesized from LA in the body; dietary sources include eggs, poultry, beef, farmed fish.

Clinical notes: Precursor to pro-inflammatory eicosanoids. AA balance with EPA/DHA determines inflammatory tone.

Gamma-Linolenic Acid (GLA, C18:3, Omega-6)

Sources: Evening primrose oil, borage oil, black currant seed oil.

Clinical notes: Unusual in that it's an omega-6 with some anti-inflammatory effects via conversion to PGE1. Used in supplementation for eczema, PMS, and inflammatory conditions with mixed evidence.

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Polyunsaturated Fatty Acids: Omega-3 Family

Alpha-Linolenic Acid (ALA, C18:3, Omega-3)

Essential fatty acid.

Sources: Flaxseed (55% of fat), chia seeds (~60%), walnuts, hemp seeds, canola oil.

Clinical notes: Plant-based omega-3. Must be converted to EPA/DHA for most biological activity — conversion is 5–10% to EPA and 0.5–5% to DHA. Conversion is higher in women (potentially due to estrogen).

Research: Burdge, G.C., & Calder, P.C. (2005). "Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults." Reproduction Nutrition Development, 45(5), 581–597.

Stearidonic Acid (SDA, C18:4, Omega-3)

Sources: Echium oil, some genetically engineered sources.

Clinical notes: Converts to EPA more efficiently than ALA (~30%); emerging alternative for plant-based EPA precursor.

Eicosapentaenoic Acid (EPA, C20:5, Omega-3)

Sources: Fatty fish (sardines, salmon, mackerel, herring, anchovies), fish oil, krill oil, algal oil.

Clinical notes: The primary anti-inflammatory omega-3. Competes with arachidonic acid for eicosanoid synthesis, shifting inflammation downward. Strong evidence for cardiovascular benefit.

Research: Calder, P.C. (2018). "Very long-chain n-3 fatty acids and human health: fact, fiction and the future." Proceedings of the Nutrition Society, 77(1), 52–72.

Docosahexaenoic Acid (DHA, C22:6, Omega-3)

Sources: Same as EPA plus algal oil specifically high in DHA.

Clinical notes: Major structural component of the brain and retina. Essential for fetal brain development; specific recommendations for pregnancy. Works synergistically with EPA for cardiovascular and anti-inflammatory effects.

Target intake (combined EPA+DHA): 250–500mg/day (FDA); 1,000mg+ daily for cardiovascular prevention.

Docosapentaenoic Acid (DPA, C22:5, Omega-3)

Sources: Seal oil, fatty fish (minor amounts).

Clinical notes: An intermediate in EPA-to-DHA conversion; under-researched but may have unique cardiovascular effects.

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Trans Fats

Industrial Trans Fats (from partial hydrogenation)

Sources (historical): Margarine, shortening, many baked goods, fried fast food.

Status in 2026: Largely banned in the US (since 2018), EU (2021), and many other jurisdictions. Historic contributor to cardiovascular mortality.

Clinical notes: The most clearly harmful dietary fat ever identified. Raises LDL, lowers HDL, promotes inflammation. WHO estimates 540,000 deaths annually preventable by global trans fat elimination.

Naturally Occurring Trans Fats

Sources: Dairy, beef, lamb (produced by ruminant gut bacteria).

Clinical notes: Includes trans-vaccenic acid and CLA (see below). Cardiovascular effects appear neutral or possibly beneficial, unlike industrial trans fats.

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Specialty and Conjugated Fatty Acids

Conjugated Linoleic Acid (CLA)

Sources: Grass-fed beef and dairy (higher than grain-fed), some supplements.

Clinical notes: A naturally occurring trans fat isomer with distinct properties. Animal research suggests anti-cancer and body composition benefits; human trials show minimal fat loss effect. Supplemental CLA has mixed evidence.

Medium-Chain Triglycerides (MCTs)

Sources: Coconut oil (~60% MCTs), palm kernel oil, MCT oil supplements (purified C8 and C10).

Clinical notes: Rapidly absorbed and converted to ketones; useful for ketogenic diets. Modest thermogenic effect (75–100 kcal/day). Doesn't raise LDL as much as long-chain saturated fats.

Research: St-Onge, M.P., & Bosarge, A. (2008). "Weight-loss diet that includes consumption of medium-chain triacylglycerol oil leads to a greater rate of weight and fat mass loss than does olive oil." American Journal of Clinical Nutrition, 87(3), 621–626.

Short-Chain Fatty Acids (SCFAs)

Sources: Produced by gut bacteria fermenting dietary fiber (not typically from dietary fat).

Key SCFAs: Butyrate (colon health), acetate (systemic), propionate (liver).

Clinical notes: The primary "health mechanism" of dietary fiber. Foods promoting SCFA production: legumes, whole grains, resistant starches, onions, garlic.

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Key Fat Metrics and What They Mean

Saturated Fat Percentage

Target: <10% of total calories (AHA/WHO); <7% for cardiovascular risk reduction.

Application: Sum all SFAs in your daily intake and divide by total calories. 2,000 kcal/day × 10% / 9 kcal/g = 22g SFA maximum.

Omega-3:6 Ratio

Target: 1:1 to 1:4 (evolutionary baseline).

Current Western reality: 1:15 to 1:25.

Application: Track both omega-3 (primarily EPA+DHA from fish; ALA from flax/chia) and omega-6 (primarily LA from oils, nuts, grains) to calculate ratio.

Unsaturated:Saturated Ratio

Target: Greater than 2:1 (unsaturated dominant).

Polyunsaturated:Monounsaturated

No specific target; emphasis on quality of PUFA (omega-3 vs omega-6 balance).

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Fat Composition of Common Foods (per 100g)

Oils

Oil	SFA	MUFA	PUFA	Omega-3	Omega-6
Olive oil (EVOO)	14g	73g	11g	0.8g	9.8g
Avocado oil	12g	71g	14g	1.0g	13g
Coconut oil	82g	6g	2g	0g	1.8g
Canola oil	7g	63g	28g	9.1g	18.6g
Sunflower oil	10g	20g	66g	0g	66g
Flaxseed oil	9g	18g	68g	53g	14g
Butter	51g	21g	3g	0.3g	2.2g
Ghee	62g	29g	4g	1.4g	2.2g

Animal proteins

Food	SFA	MUFA	PUFA	Omega-3	Omega-6
Salmon (wild, cooked)	2.1g	4.3g	4.6g	2.0g	0.3g
Sardines (canned oil)	2.3g	3.9g	5.2g	1.4g	2.5g
Grass-fed beef (85%)	6.0g	6.5g	0.5g	0.1g	0.3g
Grain-fed beef (85%)	6.0g	6.5g	0.6g	0.02g	0.4g
Whole egg	3.1g	4.1g	1.9g	0.1g	1.6g

Nuts and seeds

Food	SFA	MUFA	PUFA	Omega-3	Omega-6
Flaxseeds (ground)	3.7g	7.5g	28.7g	22.8g	5.9g
Chia seeds	3.3g	2.3g	23.7g	17.8g	5.8g
Walnuts	6.1g	8.9g	47.2g	9.1g	38.1g
Almonds	3.8g	31.6g	12.3g	0g	12.2g
Macadamia nuts	12.1g	58.9g	1.5g	0.2g	1.3g

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Practical Implications

For cardiovascular health

• Replace processed saturated and trans fats with MUFA (olive oil) and long-chain omega-3 (fatty fish)
• Maintain omega-3:6 ratio at 1:4 or better
• Include 2–3 servings of fatty fish weekly (salmon, sardines, mackerel)

For body composition

• Total fat intake: ~20–30% of calories for most goals
• MCT and omega-3 may offer modest thermogenic and anti-inflammatory benefits
• Avoid very low-fat approaches (may impair hormone production)

For brain health

• DHA is particularly important; 1g+ daily from fish or algal oil
• ALA from plants is insufficient alone; low conversion to DHA

For cooking

Match oils to cooking temperature:

Method	Best Oils
High-heat searing (>450°F)	Avocado oil, refined coconut oil
Medium roasting (350–425°F)	Olive oil, ghee, avocado oil
Low-heat sautéing	Olive oil, butter
No-heat dressings	EVOO, flaxseed oil, walnut oil

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Entity Reference

• SFA (Saturated Fatty Acid): fatty acid with no double bonds in the carbon chain.
• MUFA (Monounsaturated Fatty Acid): fatty acid with one double bond.
• PUFA (Polyunsaturated Fatty Acid): fatty acid with multiple double bonds.
• Omega position: the location of the first double bond from the methyl end of the fatty acid chain (omega-3, omega-6, omega-9).
• Essential fatty acid: fatty acids the body cannot synthesize; must come from diet (linoleic acid and alpha-linolenic acid).
• Eicosanoid: signaling molecules derived from 20-carbon fatty acids (arachidonic acid, EPA); regulate inflammation.
• PREDIMED: the Spanish Mediterranean diet trial establishing cardiovascular benefits of olive oil and nuts.
• Lipokine: a fatty acid that functions as a signaling molecule (e.g., palmitoleic acid).

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How Nutrola Tracks Fatty Acids

Nutrola is an AI-powered nutrition tracking app that tracks fatty acid composition of foods, not just "total fat":

Feature	What It Does
SFA / MUFA / PUFA tracking	Breaks down total fat by type
Omega-3:6 ratio	Calculates daily and weekly ratio
EPA+DHA target tracking	Flags days below 250–500mg minimum
Saturated fat % alerts	Warns when SFA exceeds 10% of calories
Trans fat detection	Flags any product containing trans fats

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FAQ

What is the ideal omega-3 to omega-6 ratio?

Evolutionary estimates suggest 1:1 to 1:4. Western diets average 1:15 to 1:25. Reducing seed oils and increasing fatty fish shifts the ratio favorably. Most practical target: maintain ratio below 1:8.

Is saturated fat bad?

The picture is nuanced. Industrial processed sources (fried foods, pastries) are harmful; whole-food sources (eggs, dairy, meat) are neutral for most people in moderate amounts. Aim for <10% of calories from saturated fat.

Do I need fish oil if I eat fish?

If you eat fatty fish 2–3 times per week, typically no. Otherwise, 1g+ daily of EPA+DHA from supplements is well-supported, especially if you're over 50.

Is coconut oil healthy?

It's 82% saturated fat, raising both LDL and HDL. Not "superfood" as marketed, but not clearly harmful in moderation. Better choices for regular cooking: olive oil, avocado oil.

What are MCT oils good for?

MCTs provide rapid energy via ketones; useful on ketogenic diets or for quick fuel. Modest thermogenic effect (~75 kcal/day). Don't expect dramatic fat loss from MCT supplementation alone.

Is vegetable oil really bad?

Overconsumption of industrial seed oils (soybean, corn, sunflower) at 15–25% of calories has shifted the omega-6:3 ratio dramatically. Reducing these in favor of olive oil, avocado, and butter is a legitimate dietary upgrade.

Is there a difference between grass-fed and grain-fed fat?

Yes. Grass-fed beef has a 1:2 omega-3:6 ratio vs 1:15 for grain-fed, plus 2–5× more CLA. The premium is justified for regular red meat consumers.

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References

• Estruch, R., Ros, E., Salas-Salvadó, J., et al. (2018). "Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts." New England Journal of Medicine, 378, e34.
• Calder, P.C. (2018). "Very long-chain n-3 fatty acids and human health." Proceedings of the Nutrition Society, 77(1), 52–72.
• Hunter, J.E., Zhang, J., & Kris-Etherton, P.M. (2010). "Cardiovascular disease risk of dietary stearic acid compared with trans, other saturated, and unsaturated fatty acids." AJCN, 91(1), 46–63.
• Burdge, G.C., & Calder, P.C. (2005). "Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults." Reproduction Nutrition Development, 45(5), 581–597.
• St-Onge, M.P., & Bosarge, A. (2008). "Weight-loss diet that includes consumption of medium-chain triacylglycerol oil leads to a greater rate of weight and fat mass loss than does olive oil." AJCN, 87(3), 621–626.
• Mozaffarian, D., & Wu, J.H. (2011). "Omega-3 fatty acids and cardiovascular disease." Journal of the American College of Cardiology, 58(20), 2047–2067.

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Track Fatty Acid Quality, Not Just Total Fat

Nutrola breaks down every logged food's fat content by type — SFA, MUFA, PUFA, omega-3, omega-6 — so you see the full fat picture, not just a single number.

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