Sweeteners can generally be classified as nutritive or nonnutritive. Nutritive sweeteners, which include sugar, honey, and corn syrup, for example, contribute calories and carbohydrate to the diet. Nonnutritive sweeteners, which include acesulfame K, aspartame, neotame, saccharin, and sucralose, contribute no calories or carbohydrate to the diet, either because they are not metabolized by the body, or because they are intensely sweet and therefore used in tiny quantities too small to make a difference.
Sugar alcohols. Sugar alcohols, which are often used as ingredients in “low-carbohydrate” foods, are nutritive sweeteners. In spite of label claims suggesting otherwise, sugar alcohols contribute calories and carbohydrate to the diet, and they raise blood glucose levels. Most sugar alcohols provide fewer calories than sugar (2–3 calories per gram rather than 4 calories per gram). They are also absorbed into the bloodstream more slowly than sugar, so they do not raise blood glucose levels as high, and they require less insulin to metabolize. Sugar alcohols are also less sweet than sugar, and they add bulk and moisture to foods, so they are often used in combination with nonnutritive sweeteners in foods and in products such as cough drops. Some products also combine sugar alcohols with sugar or other caloric sweeteners to create a product that’s somewhat lower in carbohydrate than one sweetened only with sugar.
Food manufacturers may voluntarily list the number of grams of sugar alcohols in a serving of food in the Nutrition Facts panel. However, if a claim such as “sugar-free” or “no added sugar” is made on the package, the sugar alcohol content must be shown in the Nutrition Facts panel, according to FDA regulations. If only one type of sugar alcohol is used, the specific name may appear in the Nutrition Facts panel, but if more than one type is used, the term “sugar alcohols” must be used. Most diabetes nutrition experts recommend counting half the grams of sugar alcohols in the portion of food you eat toward your carbohydrate total for the meal or snack.
Common sugar alcohols include erythritol, hydrogenated starch hydrolysates, isomalt, lactitol, maltitol, mannitol, sorbitol, and xylitol. If eaten in excess, sugar alcohols can cause gastrointestinal symptoms such as gas or diarrhea. The American Dietetic Association advises that more than 50 grams per day of sorbitol or more than 20 grams per day of mannitol “may cause diarrhea.” However, individual tolerance of these substances varies, and some people may be affected by as little as 10 grams of sorbitol a day. Because of these side effects, foods that contain sorbitol or mannitol and are likely to be eaten in amounts that could produce such an effect must bear the statement “Excess consumption may have a laxative effect.”
Tagatose. A relatively new reduced-calorie sweetener on the US market, tagatose occurs naturally in a variety of foods, including some dairy products, and is 92% as sweet as sucrose (table sugar). Because it is not completely absorbed by the body, it provides only around 38% of the calories of sucrose, but this incomplete absorption can lead to bloating, nausea, flatulence, and diarrhea.
Trehalose. Another relative newcomer on the US sweetener market, trehalose is a sugar that is naturally present in foods such as mushrooms and lobster. It is commercially produced from cornstarch and is approved for use in a variety of foods and beverages including nutrition bars and sports drinks. According to preliminary studies by Cargill, the company that produces trehalose, it may cause a lower insulin response than glucose. However, trehalose is only about half as sweet as sucrose.
Fructose. This sugar occurs naturally in foods such as fruit, honey, and some vegetables. Products sweetened with fructose are sometimes marketed with the claim that they raise blood glucose levels less than similar products sweetened with sucrose. It is true that pure fructose has little effect on blood glucose levels and, because of the way it’s metabolized, can be used by the body for energy without insulin. However, fructose has the same number of calories per gram as sucrose or glucose, so portion size remains important, and it’s a good idea to check the label for other ingredients, such as white flour, that have a more pronounced effect on blood glucose level.