Sugar alcohols (also called polyhydric alcohols, polyalcohols, alditols or glycitols) are

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

s, typically derived from sugars, containing one hydroxyl group (–OH) attached to each carbon atom. They are white, water-soluble solids that can occur naturally or be produced industrially by

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organ ...

of sugars. Since they contain multiple –OH groups, they are classified as

polyol In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, thr ...

s. Sugar alcohols are used widely in the food industry as thickeners and sweeteners. In commercial foodstuffs, sugar alcohols are commonly used in place of table sugar ( sucrose), often in combination with high-intensity

artificial sweetener A sugar substitute is a food additive that provides a sweetness like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie () or low-calorie sweetener. Artificial sweeteners may b ...

s, in order to offset their low sweetness.

Xylitol Xylitol is a chemical compound with the formula , or HO(CH2)(CHOH)3(CH2)OH; specifically, one particular stereoisomer with that structural formula. It is a colorless or white crystalline solid that is freely soluble in water. It can be classifi ...

and sorbitol are popular sugar alcohols in commercial foods.

Chemical structure

Sugar alcohols have the general formula HOCH₂(CHOH)_''n''CH₂OH. In contrast, sugars have two fewer hydrogen atoms, for example HOCH₂(CHOH)_''n''CHO or HOCH₂(CHOH)_''n''−1C(O)CH₂OH. The sugar alcohols differ in chain length. Most have five- or six-carbon chains, because they are derived from

pentose In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. The chemical formula of many pentoses is , and their molecular weight is 150.13 g/mol.hexose In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. The chemical formula for all hexoses is C6H12O6, and their molecular weight is 180.156 g/mol. Hexoses exist in two forms, open-chain or cyclic, that easily convert ...

s (six-carbon sugars), respectively. They have one –OH group attached to each carbon. They are further differentiated by the relative orientation ( stereochemistry) of these –OH groups. Unlike sugars, which tend to exist as rings, sugar alcohols do not. They can, however, be dehydrated to give cyclic ethers; e.g. sorbitol can be dehydrated to isosorbide.

Production

Sorbitol and mannitol

Mannitol Mannitol is a type of sugar alcohol used as a sweetener and medication. It is used as a low calorie sweetener as it is poorly absorbed by the intestines. As a medication, it is used to decrease pressure in the eyes, as in glaucoma, and to lo ...

is no longer obtained from natural sources; currently, sorbitol and mannitol are obtained by

of sugars, using Raney nickel catalysts. The conversion of glucose and mannose to sorbitol and mannitol is given as: :HOCH₂CH(OH)CH(OH)CH(OH)CH(OH)CHO + H₂ → HOCH₂CH(OH)CH(OH)CH(OH)CH(OH)CHHOH More than a million tons of sorbitol are produced in this way every year. Xylitol and lactitol are obtained similarly.

Erythritol

Erythritol Erythritol is an organic compound, a four-carbon sugar alcohol (or polyol) with no optical activity, used as a food additive and sugar substitute. It is naturally occurring. It can be made from corn using enzymes and fermentation. Its formula is ...

is obtained by the fermentation of glucose and sucrose.

Health effects

Sugar alcohols do not contribute to

tooth decay Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicatio ...

; on the contrary,

xylitol Xylitol is a chemical compound with the formula , or HO(CH2)(CHOH)3(CH2)OH; specifically, one particular stereoisomer with that structural formula. It is a colorless or white crystalline solid that is freely soluble in water. It can be classifi ...

is a deterrent to tooth decay. Sugar alcohols are absorbed at 50% of the rate of sugars, resulting in less of an effect on

blood sugar Glycaemia, also known as blood sugar level, blood sugar concentration, or blood glucose level is the measure of glucose concentrated in the blood of humans or other animals. Approximately 4 grams of glucose, a simple sugar, is present in the blo ...

levels as measured by comparing their effect to sucrose using the

glycemic index The glycemic (glycaemic) index (GI; ) is a number from 0 to 100 assigned to a food, with pure glucose arbitrarily given the value of 100, which represents the relative rise in the blood glucose level two hours after consuming that food. The GI of ...

. The unabsorbed sugar alcohols may cause bloating and

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

if consumed in sufficient amounts.

Common sugar alcohols

Ethylene glycol Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...

(2-carbon) *

Glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...

(3-carbon) *

(4-carbon) *

Threitol Threitol is a four-carbon sugar alcohol with the molecular formula C4H10O4. It is primarily used as an intermediate in the chemical synthesis of other compounds. It is the diastereomer of erythritol, which is used as a sugar substitute. In livin ...

(4-carbon) *

Arabitol Arabitol, or arabinitol, is a sugar alcohol. It can be formed by the reduction of either arabinose or lyxose. Some organic acid tests check for the presence of D-arabitol, which may indicate overgrowth of intestinal microbes such as ''Candida a ...

(5-carbon) *

Ribitol Ribitol, or adonitol, is a crystalline pentose alcohol (C5H12O5) formed by the reduction of ribose. It occurs naturally in the plant '' Adonis vernalis'' as well as in the cell walls of some Gram-positive bacteria, in the form of ribitol phosp ...

(5-carbon) *

(6-carbon) * Sorbitol (6-carbon) * Galactitol (6-carbon) *

Fucitol Fucitol, also known as L-fucitol, 6-deoxy-L-galactitol, and (2''R'',3''S'',4''R'',5''S'')-hexane-1,2,3,4,5-pentol, is a sugar alcohol derived from fucoidan which is found in the North Atlantic seaweed ''Fucus vesiculosus'' or by the reduction of ...

(6-carbon) * Iditol (6-carbon) * Inositol (6-carbon; a cyclic sugar alcohol) * Volemitol (7-carbon) *

Isomalt Isomalt is a sugar substitute, a type of sugar alcohol used primarily for its sugar-like physical properties. It has little to no impact on blood sugar levels, and does not stimulate the release of insulin. It also does not promote tooth decay an ...

(12-carbon) *

Maltitol Maltitol is a sugar alcohol (a polyol) used as a sugar substitute. It has 75–90% of the sweetness of sucrose (table sugar) and nearly identical properties, except for browning. It is used to replace table sugar because it is half as energetic, ...

(12-carbon) *

Lactitol Lactitol is a sugar alcohol used as a replacement bulk sweetener for low calorie foods with 30–40% of the sweetness of sucrose. It is also used medically as a laxative. Lactitol is produced by two manufacturers, Danisco and Purac Biochem. ...

(12-carbon) *Maltotriitol (18-carbon) *Maltotetraitol (24-carbon) *Polyglycitol Both

disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, la ...

s and monosaccharides can form sugar alcohols; however, sugar alcohols derived from disaccharides (e.g. maltitol and lactitol) are not entirely

hydrogenated Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic ...

because only one

aldehyde group In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

is available for reduction.

Sugar alcohols as food additives

This table presents the relative sweetness and

food energy Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscular activity. Most animals derive most of their energy from aerobic respiration, namely combining the carbohy ...

of the most widely used sugar alcohols. Despite the variance in food energy content of sugar alcohols, EU labeling requirements assign a blanket value of 2.4 kcal/g to all sugar alcohols.

Characteristics

As a group, sugar alcohols are not as sweet as sucrose, and they have slightly less

than sucrose. Their flavor is similar to sucrose, and they can be used to mask the unpleasant

aftertaste Aftertaste is the taste intensity of a food or beverage that is perceived immediately after that food or beverage is removed from the mouth. The aftertastes of different foods and beverages can vary by intensity and over time, but the unifying f ...

s of some high-intensity

sweeteners A sugar substitute is a food additive that provides a sweetness like that of sugar while containing significantly less food energy than sugar-based sweeteners, making it a zero-calorie () or low-calorie sweetener. Artificial sweeteners may be d ...

. Sugar alcohols are not metabolized by oral bacteria, and so they do not contribute to

. They do not brown or

caramelize Caramelization is a process of browning of sugar used extensively in cooking for the resulting sweet nutty flavor and brown color. The brown colors are produced by three groups of polymers: caramelans (C24H36O18), caramelens (C36H50O25), and ...

when heated. In addition to their sweetness, some sugar alcohols can produce a noticeable cooling sensation in the mouth when highly concentrated, for instance in sugar-free

hard candy A hard candy (American English), or boiled sweet (British English), is a sugar candy prepared from one or more sugar-based syrups that is heated to a temperature of 160 °C (320 °F) to make candy. Among the many hard candy varieti ...

chewing gum Chewing gum is a soft, cohesive substance designed to be chewed without being swallowed. Modern chewing gum is composed of gum base, sweeteners, softeners/ plasticizers, flavors, colors, and, typically, a hard or powdered polyol coating. Its t ...

. This happens, for example, with the

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

phase of sorbitol, erythritol, xylitol, mannitol,

lactitol Lactitol is a sugar alcohol used as a replacement bulk sweetener for low calorie foods with 30–40% of the sweetness of sucrose. It is also used medically as a laxative. Lactitol is produced by two manufacturers, Danisco and Purac Biochem. ...

and

maltitol Maltitol is a sugar alcohol (a polyol) used as a sugar substitute. It has 75–90% of the sweetness of sucrose (table sugar) and nearly identical properties, except for browning. It is used to replace table sugar because it is half as energetic, ...

. The cooling sensation is due to the dissolution of the sugar alcohol being an endothermic (heat-absorbing) reaction, one with a strong

heat of solution In thermochemistry, the enthalpy of solution ( heat of solution or enthalpy of solvation) is the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure resulting in infinite dilution. The enthalpy of sol ...

Absorption from the small intestine

Sugar alcohols are usually incompletely absorbed into the blood stream from the small intestine which generally results in a smaller change in

blood glucose Glycaemia, also known as blood sugar level, blood sugar concentration, or blood glucose level is the measure of glucose concentrated in the blood of humans or other animals. Approximately 4 grams of glucose, a simple sugar, is present in the blo ...

than "regular" sugar (sucrose). This property makes them popular sweeteners among

diabetic Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

s and people on

low-carbohydrate diet Low-carbohydrate diets restrict carbohydrate consumption relative to the average diet. Foods high in carbohydrates (e.g., sugar, bread, pasta) are limited, and replaced with foods containing a higher percentage of fat and protein (e.g., meat, ...

s. As an exception, erythritol is actually absorbed in the small intestine and excreted unchanged through urine, so it contributes no calories even though it is rather sweet.

Side effects

Like many other incompletely digestible substances, overconsumption of sugar alcohols can lead to

bloating Abdominal bloating (or simply bloating) is a short-term disease that affects the gastrointestinal tract. Bloating is generally characterized by an excess buildup of gas, air or fluids in the stomach. A person may have feelings of tightness, pres ...

and flatulence because they are not fully absorbed in the small intestine. Some individuals experience such symptoms even in a single-serving quantity. With continued use, most people develop a degree of tolerance to sugar alcohols and no longer experience these symptoms.

References

{{Alcohols Sugar substitutes fr:Polyol