DF are highly complex substances that can be described as any nondigestible carbohydrates and lignins not degraded in the
upper gut
Commonly, DF are classified according to their solubility in water, even though grading according to viscosity, gel-forming
capabilities, or fermentation rate by the gut microbiota might be physiologically more relevant
Main sources of soluble
DF are fruits and vegetables
n increased intake of total DF was inversely associated with markers of insulin resistance in several studies
consumption of insoluble DF increased whole
body glucose disposal independent of changes in body weight in both short-term and more prolonged studies
Short-chain fatty acids (SCFA) such as acetate, propionate, and butyrate are produced by bacterial fermentation of indigestible
DF polysaccharides in the colon
increased production of SCFA is assumed to be beneficial by reducing hepatic glucose output and improving lipid
homeostasis
a high DF diet (oligofructose) reduced gram-negative bacterial content and body weight, whereas a high fat
diet increased the proportion of a gram-negative bacterial lipopolysaccharides (LPS) containing microbiota in humans
Prospective cohort studies indicate that diets high in insoluble cereal DF and whole grains might reduce diabetes risk