Sugar alcohols, a family of sweetening agents also known as "polyols", are used as food additives. They occur naturally in small amounts in fruits and vegetables, including berries, apples, and plums, but for large-scale commercial use they are manufactured from common sugars. While they are chemically very similar to sugars, they are less sweet than sugars and have fewer calories per gram.
Before any food additive is permitted to be used in foods sold in Canada, it is evaluated by Health Canada scientists to determine that it is safe, and achieves its intended purpose. Permitted food additives are listed under Division 16 of the Food and Drug Regulations.
Currently the following sugar alcohols are permitted for use as food additives in Canada: hydrogenated starch hydrolysates, isomalt, lactitol, maltitol, maltitol syrup, mannitol, sorbitol, sorbitol syrup, xylitol and erythritol.
Another food additive, polydextrose, a compound synthesized from dextrose (glucose), is also permitted. Because it has a low digestible energy value, it is used to provide bulk in foods, thereby reducing the caloric content. Unlike polyols, polydextrose is not sweet but has a slightly tart taste and thus can add texture to food without adding sweetness. It is often used as a replacement for sugar, starch, and fat in foods such as cakes, candies, pudding, and desserts.
Health Canada scientists have studied the human health effects of these compounds and have concluded that the addition of sugar alcohols and/or polydextrose to foods is safe and that they are effective sweetening or texturizing/bulking agents. It is known, however, that eating too much of these substances can cause gastro-intestinal discomfort and laxative effects. This is a result of sugar alcohols and polydextrose being poorly taken up from the gastrointestinal tract. The likelihood of such effects occurring is related to the amount consumed and, therefore, increases with the consumption of more than one product containing sugar alcohols and/or polydextrose. There is a wide variation, however, in sensitivity between individuals to these effects. Also, it is possible with frequent consumption of products containing sugar alcohols and/or polydextrose to develop a tolerance, and be able to increase consumption without experiencing adverse effects.
In order to assist individuals in learning to recognize the amount of sugar alcohols and polydextrose they can tolerate, the Food and Drug Regulations (Sections B.01.018 and B.01.021) require that foods containing sugar alcohols and/or polydextrose carry a statement identifying their total content expressed in grams per serving of a stated size. In the case of those foods in which the product label carries a Nutrition Facts table, the Regulations require that the Nutrition Facts table show the amount of sugar alcohols added to the product. Consumers can then determine their potential intake of these substances from a food product and avoid intakes that they recognize in themselves as causing abdominal cramps and diarrhea.
Mannitol and sorbitol, along with other sugar alcohols, have been promoted as useful sugar substitutes for diabetics. Unlike sucrose and glucose which cause quick changes in blood glucose concentration, these sugar alcohols do not produce significant changes in blood glucose concentration because, once absorbed, they are converted to energy by processes that require little or no insulin. People with diabetes, however, should consult their physician or other health professionals about the usefulness of sugar alcohols in their diet before increasing the amount of foods they eat that contain these substances.
Sugar alcohols are also resistant to metabolism by the bacteria in the mouth which break down sugars and starches to release decay-causing acids. As a result, sugar alcohols in general are considered not to promote tooth decay. Studies have indicated that xylitol in particular may actually help to prevent tooth decay.
The following table highlights some of the key properties of specific sugar alcohols and polydextrose.
|Sweetener/ Name of Compound||% Relative Sweetness vs. Sucrose (normal sugar)||Impact on Blood Sugar and Insulin Secretion||Calorie Value kcal/g||Derived From|
|Mannitol||50 - 70||Low||1.6||Fructose|
|Sorbitol||50 - 70||Low||2.6||Glucose|
|Sorbitol Syrup||25 - 50
(depending on sorbitol content)
|Low||3||Corn, Wheat or Potato Starch|
|Maltitol||90||Low||3||High Maltose Corn Syrup|
|Maltitol Syrup||25 - 50
(depending on maltitol content)
|Low||3||Corn, Wheat or Potato Starch|
|Lactitol||30 - 40||Low||2||Lactose|
|Isomalt||45 - 65||Low||2||Sucrose|
|Erythritol||60 - 80||Low||0.2||Glucose|
|Polydextrose||0||Low||1||Dextrose (Glucose), Sorbitol & Citric or Phosphoric Acid|
Overall, the benefits of permitting the use of sugar alcohols and polydextrose as food additives in certain foods are greater than the potential for laxative effects that could result from excessive consumption of these substances. Health Canada, however, considers that it is important for consumers to be made aware that sugar alcohols and/or polydextrose are added to certain foods, to recognize the names of these compounds and to be aware that excessive consumption of such foods could lead to gastro-intestinal discomfort and laxative effects.