The Sweetening Power of Polyols

With America's growing concern over obesity and diabetes, polyols may appear on ingredient lists more often in the future. "There is absolutely a recent increase in demand for polyols because of the popularity of low-carbohydrate diets," says Donna Brooks, product manager, Danisco Sweeteners, Ardsley, NY.  

"Today's demand for some polyols, like isomalt and maltitol, is exceeding the output," says Ron Perko, business development manager for polyols, Cargill, Minneapolis.  

Polyols -- sugar-free sweeteners also known as sugar alcohols or sugar replacers -- have filled a niche in food production for years. Not only do they provide fewer calories per gram compared to nutritive sugars, they are versatile food additives, serving as humectants, bulking agents and freeze-point depressants.  

Some people seem to be born with a sweet tooth, although sweetness perception varies and has been linked to many factors, including genetics. The nation's penchant for sweets has prompted the Washington, D.C.-based Institute of Medicine to suggest that diet quality suffers when people consume more than 25% of their total energy in sugars. Most folks don't come close to this level, but one in four children between the ages of nine to 18 surpass it. Sugar intake can also increase the risk of dental caries, and high-fructose consumption may cause hypertriglyceridemia and gastrointestinal symptoms in some individuals.

Currently, no research directly links sugar alone to an increased risk of obesity, but consuming sugar substitutes that provide less calories per gram can aid weight management. About nine out of 10 U.S. consumers turn to low-calorie products, including sugar-free foods and beverages.   

If they replace sugar, polyols can create a sugar-free label. Unlike high- potency, nonnutritive sweeteners, which are used in very small amounts, polyols are carbohydrates used in approximately the same quantity as sucrose.

Polyols provide fewer calories because the intestine absorbs them slowly and incompletely by passive diffusion. Incomplete absorption causes indirect metabolism via fermentative degradation by the intestinal flora. Products with sorbitol and mannitol must carry a warning label, "Excess consumption may have a laxative effect," because they increase the risk of malabsorption.

Chemically, polyols are considered polyhydric alcohols or sugar alcohols, because part of their structure resembles sugar and part is similar to alcohols. They are derived from carbohydrates whose carbonyl group has been reduced to a primary or secondary hydroxyl group. Polyols can have a chemical structure that is monosaccharide-derived, such as sorbitol, mannitol, xylitol and erythritol; disaccharide-derived mixtures like isomalt, lactitol or maltitol; or polysaccharide-derived mixtures, such as maltitol syrup or hydrogen hydrolysates. Many polyol sweeteners occur naturally in plants, but they also are produced for commercial use. The most widely used polyols are sorbitol, mannitol and maltitol.

"We are seeing a tremendous interest in erythritol. Most polyols contain 2 to 3 calories per gram, while erythritol contains 0.2 calories per gram. It is a very small molecule and is absorbed in the small intestine, and this makes its digestive tolerance much higher than other polyols," says Perko.  

Many foods utilize polyols, such as chewing gums, candies, ice cream, baked goods and fruit spreads. They also function well in fillings, frostings, canned fruits, beverages, yogurt and tabletop sweeteners. "Polyols are being used in many new products. There has been a history of using polyols for the sugar-free niche market, but it is expanding to mainstream consumers as a result of their interest in reducing sugar intake," says Brooks.  

Molds and bacteria do not grow well on polyols (compared with sugars), so shelf life may be longer in products that contain them. Since there is no loss of sweetness in heating, polyols may be used in hot beverages and foods that are heated, but they don't provide the crisp brown surface on baked foods that sugar does.

Sugar replacers often are combined with other alternative sweeteners, like aspartame or saccharin, as the polyol contributes a mild sweetness along with the bulk and texture of sugar, while the other alternative sweetener brings the sweetness level up.  

Polyols are regulated as either GRAS or food additives. In nutrition labeling, the polyol content must be displayed in the Nutrition Facts panel if a "sugar-free" claim is made about the product. If more than one polyol is used, the term "sugar alcohols" must be used on the label. In the United States, FDA must approve the safety of all potential food-additive sweeteners. Each polyol has a different regulatory status. An Acceptable Daily Intake (ADI) also is established (which varies for each polyol). The ADI is the estimated amount per kilogram of body weight that a person can safely consume on average every day over a lifetime without risk. The ADI usually reflects an amount 100 times less than the maximum level at which no observed effect occurs in animals.  

Recent attention has focused on the potential health benefits of polyols. Nutrition Research Reviews (Dec. 2003) reported that improved glucose control was seen during a 12-week study with type 2 diabetes patients consuming polyols. The same article noted that polyols contribute toward short-chain organic acid formation for a healthy colonic epithelium. Polyols also are noncariogenic; hence FDA authorizes the health claim, "does not promote tooth decay" for erythritol, hydrogenated starch hydrolysates, isomalt, lactitol, maltitol, mannitol, sorbitol, xylitol or a combination of these in sugar-free foods that don't lower   plaque pH below 5.7.

With consumers counting up carbohydrates like dollars, polyols are likely to be star ingredients in many products on supermarket shelves in the future.

Sharon Palmer is a registered dietitian with a 16-year career in health-care food and nutrition management. She now focuses her interest on the world of journalism as a freelance writer and editor, cookbook contributor and culinary instructor.

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