Sugar Alcohols (Polyols) - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 50

alcohol group that replaces the carbonyl group and the occurrence of saccharide linkages other than
the α (1-4) and α (1-6) present in starches and sucrose. Thus, a low digestibility and/or slow hepatic
glucose release is the determinant of their low glycemic and insulinemic response properties (Table
3.3; Livesey 2003).

• Polyols are resistant to fermentation and acidogenesis by the microorganisms of dental plaque

(Willibald-Ettle and Schiweck 1996; Kandelman 1997). They are also not absorbed through the
stomach. Monosaccharide absorption along a concentration gradient does not occur by passive dif-
fusion (Herman 1974). Other polyols, disaccharide, and higher polyols are too large to diffuse from
the gut into the circulation in amounts more than 2% of oral intake (Livesey 1992). Some disac-
charide, oligosaccharide, and polysaccharide polyols may release glucose, but their digestion is slow
and incomplete. Due to the slow and incomplete digestion, the blood glucose level does not rise. It
is possible that due to the less permeability of small intestine, monosaccharide polyols may be more
readily absorbed than their coreleased monosaccharide polyols. After absorption, monosaccharide
polyols are excreted by the kidneys, oxidized directly, or converted to glycogen or glucose in the
liver. The metabolism pathway and excretion are dependent on the polyol structure. Any unabsorbed
carbohydrates from polyols are generally fermented completely by the colonic microlora (Table 3.6;
Livesey 1992).

• Many low-calorie and sugar-free foods are sweetened with polyols.

As a result of these indings, the United States Food and Drug Administration has approved a
“does not promote tooth decay” health claim for sugar-free foods and beverages sweetened with
polyols (Deis 2005; U.S. Department of Agriculture 1995). In addition, the American Dental
Association (1998) has issued an oficial statement saying that sugar-free foods do not promote
dental caries.
Except for erythritol, which is a four-carbon symmetrical polyol and exists only in the meso
form, the majority of sugar alcohols are produced industrially by hydrogenation in the presence of
Raney-nickel as a catalyst from their parent-reducing sugar (Wang 2003). Both disaccharides and
monosaccharides can form sugar alcohols; however, sugar alcohols derived from disaccharides (e.g.,
maltitol and lactitol) are not entirely hydrogenated because only one aldehyde group is available for
reduction. The simplest sugar alcohol, ethylene glycol, is the sweet, but notoriously toxic, chemical
used in antifreeze. The higher sugar alcohols are, for the most part, nontoxic (Wang 2003).
All the sugar alcohols are acyclic polyols since they contain three or more hydroxyl groups.
Polyols naturally occur in many plants. For example, sorbitol is found in various berries and some
higher plants (Lohmar 1962). One of the widely distributed polyols, d-mannitol, is being most

table 3.6 Digestibility of Common Sugar alcohols

Fermentation
(g/100 g)

absorption
(g/100 g)

Urinary Secretion
(g/100 g)

polyol

Lactitol 98 2 <2

Isomalt 90 10 <2

Mannitol 75 25 25

Sorbitol 75 25 <2

Maltitol 60 40 <2

Xylitol 50 50 <2

Erythrithol 10 90 90

Polyglycitol 60 a 40 a <2

Maltitol syrup
Regular, intermediate, high

ca. 50 b ca. 50 b <2

high polymer ca. 50 b ca. 50 b <2

a Based on in vitro digestion.
b Data based solely on glycemic and insulinemic responses.