Short-chain fatty acids (SCFAs) are fatty acids of two to six carbon atoms. Derived from intestinal microbial fermentation of indigestible foods, SCFAs in human gut are acetic, propionic and butyric acid. Butyrate is the main energy source of colonocytes, making them crucial to gastrointestinal health. SCFAs all possess varying degrees of water solubility, which distinguishes them from longer chain fatty acids that are immiscible.

List of SCFAs

Lipid numberNameSalt/Ester NameFormulaMass (g/mol)Diagram
CommonSystematicCommonSystematicMolecularStructural
C2:0Acetic acidEthanoic acidAcetateEthanoateC2H4O2CH3COOH60.05
C3:0Propionic acidPropanoic acidPropionatePropanoateC3H6O2CH3CH2COOH74.08
C4:0Butyric acidButanoic acidButyrateButanoateC4H8O2CH3(CH2)2COOH88.11
C4:0Isobutyric acid2-Methylpropanoic acidIsobutyrate2-MethylpropanoateC4H8O2(CH3)2CHCOOH88.11
C5:0Valeric acidPentanoic acidValeratePentanoateC5H10O2CH3(CH2)3COOH102.13
C5:0Isovaleric acid3-Methylbutanoic acidIsovalerate3-MethylbutanoateC5H10O2(CH3)2CHCH2COOH102.13
C5:02-Methylbutyric acid2-Methylbutanoic acid2-Methylbutanoate2-MethylbutanoateC5H10O2CH3CH2CH(CH3)COOH102.13

Functions

SCFAs are produced when dietary fiber is fermented in the colon. Acetate, propionate and butyrate are the three most common SCFAs. SCFAs and medium-chain fatty acids are primarily absorbed through the portal vein during lipid digestion, while long-chain fatty acids are packed into chylomicrons, enter lymphatic capillaries, then transfer to the blood at the subclavian vein.

SCFAs have diverse physiological roles in body functions, affecting the production of lipids, energy, and vitamins. Butyric acid supports large intestine health as the primary energy source for colonocytes – the epithelial cells of the colon. The liver can use acetate for energy.

See also

Further reading