The behavior of polyols, and other carbohydrates, in the human digestive system varies depending on their molecular size and chemical nature.

The simple monosaccharides are directly absorbed through the cell layer of the intestine. Their rate of absorption depends upon active and passive uptake. Glucose for instance is actively, and therefore rapidly, and completely absorbed. In its subsequent metabolism it contributes an energy value of 4 kcal/g.

Disaccharides first need to be hydrolyzed by the intestinal enzymatic systems before they can be absorbed.

Polysaccharides such as starch due to their complex, often branched, structures are only absorbed to the extent the digestive enzymatic system is capable of liberating the essential monosaccharide building blocks.

Absorbed monosaccharides are transported in the body and are oxidized to CO2 to provide energy or are metabolized to other substances such as glycogen or fats for energy storage. The remaining undegraded polysaccharide structures are then subjected to microbial fermentation in the large intestine where the resulting production and subsequent absorption of volatile fatty acids may contribute additional energy. At this stage gases such as methane (CH4) and hydrogen (H2) are also produced. Any undigested carbohydrate is excreted with the microbial biomass in the faeces.

Sorbitol, mannitol and xylitol, the monosaccharide polyols, can be directly absorbed while maltitol and isomalt, the disaccharide polyols, first need to be hydrolyzed to their sorbitol, mannitol and glucose building blocks before absorption is possible. The cells in the digestive system cannot actively transport polyols through the cell membrane. Polyols are therefore absorbed by a passive diffusion (osmotic) which is much slower and incomplete than the active transport. The absorbed part, in its subsequent metabolism, contributes an energy value of 4 kcal/g, as for glucose. However, erythritol is not metabolized and therefore hardly contributes any energy. The major, not absorbed part of the monosaccharide polyols, is fermented by the microflora in the large intestine to give volatile fatty acids. This fermentation contributes an energy value of 2 kcal/g.