Short-chain fatty acids (SCFAs) arefatty acids of two to sixcarbonatoms.[1] The SCFAs' lower limit is interpreted differently, either with one, two, three or four carbon atoms.[citation needed] Derived fromintestinalmicrobialfermentation of indigestible foods, SCFAs in human gut are acetic, propionic and butyric acid. They are the main energy source ofcolonocytes, making them crucial togastrointestinal health.[1][2] SCFAs all possess varying degrees of water solubility, which distinguishes them from longer chain fatty acids that are immiscible.
| Lipid number | Name | Salt/Ester Name | Formula | Mass (g/mol) | Diagram | |||
|---|---|---|---|---|---|---|---|---|
| Common | Systematic | Common | Systematic | Molecular | Structural | |||
| C2:0 | Acetic acid | Ethanoic acid | Acetate | Ethanoate | C2H4O2 | CH3COOH | 60.05 |  |
| C3:0 | Propionic acid | Propanoic acid | Propionate | Propanoate | C3H6O2 | CH3CH2COOH | 74.08 |  |
| C4:0 | Butyric acid | Butanoic acid | Butyrate | Butanoate | C4H8O2 | CH3(CH2)2COOH | 88.11 |  |
| C4:0 | Isobutyric acid | 2-Methylpropanoic acid | Isobutyrate | 2-Methylpropanoate | C4H8O2 | (CH3)2CHCOOH | 88.11 |  |
| C5:0 | Valeric acid | Pentanoic acid | Valerate | Pentanoate | C5H10O2 | CH3(CH2)3COOH | 102.13 |  |
| C5:0 | Isovaleric acid | 3-Methylbutanoic acid | Isovalerate | 3-Methylbutanoate | C5H10O2 | (CH3)2CHCH2COOH | 102.13 |  |
| C5:0 | 2-Methylbutyric acid | 2-Methylbutyric acid | 2-Methylbutanoate | 2-Methylbutanoate | C5H10O2 | CH3CH2CH(CH3)COOH | 102.13 |  |
SCFAs are produced whendietary fiber is fermented in thecolon.[1][3] Macronutrient composition (carbohydrate, protein or fat) of diets affects circulating SCFAs.[4] Acetate, propionate and butyrate are the three most common SCFAs.[3]Butyrate is particularly important forcolon health because it is the primary energy source forcolonocytes (the epithelial cells of the colon).[1][2] The liver can use acetate for energy.[5]
SCFAs andmedium-chain fatty acids are primarily absorbed through theportal vein duringlipid digestion,[6] whilelong-chain fatty acids are packed intochylomicrons, enterlymphatic capillaries, then transfer to the blood at thesubclavian vein.[1]
SCFAs have diversephysiological roles in body functions, affecting the production of lipids, energy, and vitamins.[1][2][7] They may affect appetite and cardiometabolic health.[4]