Sugar Alcohols Occurrence

Sugar alcohols of exogenous origin—if consumed in limited amounts—have no disease-causing effects. Many occur in plants and lower organisms (A); some are produced technically, often by hydrogenation of glucose syrup (B).

Naturally occurring sugar alcohols do not play a major quantitative role in nutrition. However, sugar alcohols added to foods during processing may become significant, depending on the amounts consumed. The food industry uses them for the following purposes:

  • As alternative sweeteners
  • To slow crystallization
  • As a softener
  • To decrease water availability to microorganisms (preservative)
  • To improve rehydration of dry products

All these applications arise from the sugar alcohols' common properties: they are sweet and hygroscopic. The relative sweetening power of sugar alcohols is about 60 % compared to sucrose. Therefore, they have to be used in larger amounts to achieve the same perception of sweetness. Because of their hygroscopic nature, this has unwanted consequences for digestive system function. Since many sugar alcohols are poorly absorbed, they may—if consumed in large amounts—reach distal sections of the intestinal tract. There, their hygroscopic nature makes them the cause of diarrhea.

alcohols in favor of small amounts of sucrose. This reversal of the strict interdiction on sugar consumption for diabetes mellitus patients is a result of improved therapeutic possibilities, which can be adapted to virtually any nutritional situation. It should be pointed out that these recommendations apply to very well-trained diabetics. Sugar alcohols still play a role in the nutrition of less well-trained patients.

Since the energy content of most sugar alcohols (with the exception of maltitol) is equivalent to that of the monosaccha-rides they are derived from, they have no relevant role in reduced-calorie products.

They are also used in solutions for parenteral nutrition, another important application. Since many indications for parenteral nutrition are accompanied by metabolic problems with glucose use, sugar alcohols represent an attractive source of carbohydrates.

Prevention of tooth decay is frequently cited as a further indication for sugar alcohol use. It should be mentioned here, that the most common representatives like sorbitol are actually rather easily fermented by cariogenic bacteria. Disaccharide alcohols are second generation alternative sweeteners. They are not cariogenic and are hydrolyzed and absorbed very slowly in the intestine; hence, they have hardly any impact on blood glucose levels.

Nowadays, their use as alternative sweeteners is most common in diet foods for diabetics, based on their largely insulin-independent metabolic use. However, in recent times, it has been recommended that diabetics avoid sugar

- A. Naturally Occurring Sugar Alcohols

Polyalcohol

Erythritol

Arabitol Ribitol

Xylitol

Sorbitol

D-Mannitol

Galactitol Dulcitol

Occurrence

Algae, grasses, fungi, various bacteria, human urine, fermented syrup

Fungi, lichens, yeasts, higher plants, human body fluids (liquor) and tissue (brain)

Lichens, fungi, yeasts, higher plants, human body fluids, nectar; component of various liposaccha-rides and of riboflavin

Various microorganisms, lower and higher plants (much higher concentrations then sorbitol or D-manni-tol), animal tissues

Algae, fungi, many higher plants, animal tissues

Bacteria, algae, grasses etc., including higher plants

Algae, fungi, higher plants

Characteristics

Its vasodilative effect has been investigated. Cariogenicity and physiological significance not sufficiently clear to date

Poorly metabolized by mammals (can be used as low-calorie sweetener). Large amounts are excreted with the urine. Cariogenicity studies lacking

Involved in pentose phosphate cycle. Less antiketogenic and metabolized more slowly than xylitol

Absorbed very slowly in human gastrointestinal tract. Precursor of liver glycogen. Used in enteral and parenteral feeding and as alternative sweetener for diabetics and for noncariogenic nutrition

Absorbed more slowly than glucose and used as alternative sweetener for diabetics. Precursor in of liver glycogen. Used preferentially in food processing and as sweetener. Fermented by cariogenic bacteria

Absorbed more slowly than sorbitol and xylitol; precursor of liver glycogen. Stronger laxative effect than sorbitol and xylitol. Most ingested mannitol reaches the urine unchanged. Cariogenic effect similar to that of sorbitol

Precursor of liver glycogen. Poorly absorbed. Cariogenic effects not investigated

B. Synthetic Sugar Alcohols

Polyalcohol

Occurrence

Characteristics

Lactitol

Natural occurrence not proven

Hydrolyzed to galactose and sorbitol in gastrointestinal tract by duodenal glucosidases. Its carbon skeleton may be broken down completely in the small intestine. Apparently noncariogenic; human long-term studies lacking

Maltitol

Natural occurrence not proven

Slowly hydrolyzed to glucose and sorbitol in small intestine. Noncariogenic. Used as sweetener in various foods (~ 2 kcal/g)

Isomaltitol

Natural occurrence not proven

Lower-level caloric utilization observed in rats. Cariogenicity studies lacking; behaves like lactitol and maltitol

Palatinite

Natural occurrence not proven

Caloric utilization ~ 50%. Metabolism and cario-genic effects like lactitol and maltitol

Maltotriitol Maltotetraitol

Not found to occur naturally to date

Intestinal breakdown. Inhibit amylase

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