Table 2.
Overview of fatty acids and features.
| Fatty acid group | Definition | Predominant fatty acid representativesb | Notes on nutritionc | Notes on mucosal immunity |
|---|---|---|---|---|
| Short chain fatty acid (SCFA)a | <6 carbon atoms No double C:C bonds |
Formic (simplest carboxylic acid) acetic (C2:0), propionic (C3:0), butyric (C4:0) and Isobutyric, Valeric (C5:0) and Isovaleric |
Butyric acid: various mixtures of dietary fibers, some types of resistant starch, fructo-oligosaccharides, beta-glucan. Acetic acid: mainly pectins. Proprionic acid: mainly guar gum |
Regulation of colonic Treg pool. Modulation of Nf-KB via HDAC inhibition may facilitate the anti-inflammatory response by active suppression of pro-inflammatory cytokine production |
| Medium-chain fatty acid (MCFA) | C6–C12 No double C:C bonds |
Caproic (C6:0), caprylic (C8:0), capric (C10:0), lauric (C12:0) | Coconut oil and palm kernel oil provide rich sources of straight chain MCFAs; lauric acid (C12:0), followed by caproic acid (C6:0), caprylic acid (C8:0), and capric acid (C10:0) | Lauric acid is a TLR agonist (TLR4), but also forms monolaurin in gut, a potent antimicrobial, antifungal |
| Long Chain Fatty acid (LCFA), Saturated | C14–C21 One or more double C:C bonds |
Myristic (C14:0), palmitic (C16:0), palmitate (16:1), stearic (C18:0), stearate (C18:1), arachidic (C20:0). | Palmitic and stearic acid inherently part of vegetable oils. Coconut oil source of myristic acid | Depending on chemical structure, LCFAs impact membrane structure and fluidity and many are directly involved in intracellular signaling pathways, including receptor operated calcium channels |
| LCFA, Monounsaturated | C14–C21 One double C:C bond in position carbon 9 (Δ9) |
Myristoleic (C14:1, cis-n-5;), palmitoleic (C16:1, cis-n-7), sapienic (C16:1, n-10), oleic (C18:1, cis-n-9), elaidic (C18:1, n-9), vaccenic (C18:1, cis-n-7), gondoic (C20:1, cis-n-9), erucic (C22:1, cis-n-9,), nervonic (C24:1, cis-n-9). Those not synthesized de novo include: gadoleic (C20:1, cis-n-11) and cetoleic (C22:1, cis-n-11) | Olive oil is one of the richest dietary sources, mainly due to oleic acid (78.4% ± 4.3), followed by canola, peanut (groundnut oil), avocado, hazelnut, and sweet almond oil. Rice bran, corn, and sesame oils in lower quantities | Lack of effect on eicosanoid biosynthesis. Modulate COX-2 expression |
| LCFA, Polyunsaturated | C14–C21 One or more double C:C bonds |
Omega-3: ALA (18:3), EPA (20:5), DHA (22:6) Omega-6: LA (18:2), CLA (cis-9, cis-12 cis-18, cis-2) GLA (18:3), calendic acid (C18:3), Eicosadienoic acid (C20:2), dihomo-gamma-linoleic acid (DGLA, 20:3) and ARA (20:4) |
EPA, DHA: murine fish oil or endogenous metabolic conversion via ALA. ALA: humans unable to synthesize, acquired only through dietary sources. LA: canola, corn, palm, soybean, sunflower, rice bran, and rapeseed oil. CLA: meat and dairy products. | EPA- and DHA-derive anti-inflammatory molecules protectins and resolvins ARA-derived pro-inflammatory compounds, prostaglandins and leukotrienes involved in inflammation n-3 LCFAs compete with the n-6 precursors involved in eicosanoid synthesis and serve as substrates for potent lipid mediators |
aMost SCFA are naturally saturated given the low number of carbons available for double C:C bonding saturation.
bIncomplete list of fatty acid isomers, but these are less understood, and present in the diet at a fraction of the lowest fatty acids listed.