Food Safety Focus (221st Issue, December 2024) – Article 2
Sugar Alcohols – an Overview
Reported by Ms. Sosanna WONG, Scientific Officer
Risk Assessment Section, Centre for Food Safety
In the last issue, we have discussed some sweeteners like aspartame and saccharin. In contrast to those non-nutritive sweeteners, there are in fact some other “non-sugar” sweetening substances that contain calories. In this article, let us continue our sweet journey with sugar alcohols, also known as polyols or polyhydric alcohols, which are nutritive sweeteners.
What are Sugar Alcohols?
Some people may wonder whether sugar alcohols belong to sugar or alcohol. Sugar alcohols are carbohydrates the chemical structures of which resembles both sugar and alcohol. However, they are different from sugar and do not contain ethanol (the type of alcohol present in alcoholic beverages).
In fact, sugar alcohols are naturally found in small quantities in a range of fruits and vegetables such as apples and mushrooms. They can also be produced from sugars and starches in larger quantities for commercial use. Examples of sugar alcohols include sorbitol, xylitol, erythritol, mannitol and maltitol.
Figure 2: Chemical structures of sugar alcohol (e.g. sorbitol), sugar (e.g. glucose) and alcohol (e.g. ethanol and propanol)
Properties of Sugar Alcohols
Although sugar alcohols have a sweet taste, they are typically not sweet as table sugar, in contrast to non-nutritive sweeteners that have an intense sweetness. They range from 25% to 100% of table sugar in terms of sweetness. Nowadays, sugar alcohols are often used in combination with non-nutritive sweeteners to create a better flavour profile. Sugar alcohols are commonly used as some of the sugar substitutes in sugar-free and sugar-reduced products, including candies, chewing gum, cookies and ice cream.
Beyond just adding sweetness, sugar alcohols also serve several purposes in food. Similar to sugars, sugar alcohols in food add bulk and texture. They also help food retain moisture and prevent browning when heated, making them food additives with multiple technological functions.
Since sugar alcohols are slowly and incompletely absorbed from the small intestine into the blood, they provide fewer calories per gram (approximately 0.2 to 3 kcal per gram) compared with sugar, which has about 4 kcal per gram, and produce a smaller change in blood glucose than other carbohydrates such as sucrose and glucose.
Unlike sugar, sugar alcohols are considered not to promote tooth decay because they are resistant to metabolism by bacteria in the mouth that break down sugars and starches to release decay-causing acids. When added to food in high quantities, sugar alcohols also produce a cooling sensation in the mouth, which goes well with the flavour of mint. For this reason, they are frequently found in sugar-free chewing gum and candies.
Safety of Sugar Alcohols
Concerns have been raised regarding the potential health risk of sugar alcohols. For instance, the results of some studies suggested a possible association between higher circulating blood levels of erythritol and cardiovascular disease and related risk factors. However, the European Food Safety Authority (EFSA) in its evaluation published in 2023 considered that the available studies had not demonstrated a causal relationship between dietary exposure to erythritol and the risk of cardiovascular diseases.
Like other food additives, sugar alcohols have undergone rigorous safety evaluation before permitted for use in food. In fact, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) have evaluated the safety of some sugar alcohols, namely erythritol, isomalt, lactitol, maltitol, maltitol syrup, mannitol, polyglycitol syrup, sorbitol, sorbitol syrup and xylitol, and established Acceptable Daily Intakes (ADIs) as “not specified” for them, meaning that their use as food additives does not represent a health concern.
| Sugar alcohols |
Relative sweetness vs |
Calorie value (kcal per gram) |
|---|---|---|
| Erythritol | 60 – 80% | 0.2 |
| Isomalt | 45 – 65% | 2 |
| Lactitol | 30 – 40% | 2 |
| Maltitol | 90% | 3 |
| Maltitol syrup | 25 – 50% | 3 |
| Mannitol | 50 – 70% | 1.6 |
| Polyglycitol syrup | 40 – 90% | 3 |
| Sorbitol | 50 – 70% | 2.6 |
| Sorbitol syrup | 25 – 50% | 3 |
| Xylitol | 100% | 3 |
| Compared with: table sugar | 100% | 4 |
Figure 3: Relative sweetness and calorie value of sugar alcohols
However, when consumed in excess, sugar alcohols can cause laxative effects and gastrointestinal discomforts, including abdominal gas and bloating, in some individuals. This occurs because sugar alcohols are not completely absorbed in the intestine. The likelihood of experiencing such effects depends on the quantity consumed. Therefore, it is important that manufacturers use sugar alcohols in accordance with Good Manufacturing Practice (GMP) i.e. limited to the lowest possible level necessary to accomplish the desired effect.
Local and International Situation
In Hong Kong, under the existing Sweeteners in Food Regulations (Cap. 132U), sweetener means any chemical compound which is sweet to the taste, but does not include any sugars or other carbohydrates or polyhydric alcohols (i.e. sugar alcohols). Even though sugar alcohols are currently not under the regulatory scope of Cap. 132U, they can still be used in food in accordance with GMP.
Internationally, the aforementioned ten sugar alcohols evaluated by JECFA are considered as sweeteners by the Codex Alimentarius Commission. Besides, according to the General Standard for Food Additives, they are all permitted for use in food when utilized in compliance with the principles of GMP.