A
sugar alcohol (also known as a
polyol,
polyhydric alcohol,
polyalcohol, or
glycitol) is a
hydrogenated form of
carbohydrate, whose
carbonyl group (
aldehyde or
ketone,
reducing sugar) has been reduced to a primary or secondary
hydroxyl group (hence the
alcohol). Sugar alcohols have the general formula H(HCHO)
n+1H, whereas sugars have H(HCHO)
nHCO. In commercial foodstuffs sugar alcohols are commonly used in place of table sugar (
sucrose), often in combination with high intensity
artificial sweeteners to counter the low sweetness. Of these,
xylitol is perhaps the most popular due to its similarity to sucrose in visual appearance and sweetness. Sugar alcohols do not contribute to tooth decay.
However, consumption of sugar alcohols does affect blood sugar levels. Sugar alcohols may also cause bloating and diarrhea when consumed in excessive amounts.
Some common sugar alcohols:
The simplest sugar alcohols,
ethylene glycol and
methanol, are sweet but notoriously toxic chemicals used in
antifreeze. The more complex sugar alcohols are for the most part nontoxic.
Sugar alcohols as food additives
As a group, sugar alcohols are not as sweet as
sucrose, and they have less
food energy than sucrose. Their flavor is like sucrose, and they can be used to mask the unpleasant
aftertastes of some high intensity
sweeteners. Sugar alcohols are not metabolized by oral bacteria, and so they do not contribute to
tooth decay. They do not brown or
caramelize when heated.
In addition to their sweetness, some sugar alcohols can produce a noticeable cooling sensation in the mouth when highly concentrated, for instance in sugar-free
hard candy or
chewing gum. This happens, for example, with the
crystalline phase of
sorbitol,
erythritol,
xylitol,
mannitol,
lactitol and
maltitol. The
cooling sensation is due to the dissolution of the sugar alcohol being an endothermic (heat-absorbing) reaction, one with a strong
heat of solution.
Sugar alcohols are usually incompletely absorbed into the blood stream from the
small intestines which generally results in a smaller change in
blood glucose than “regular” sugar (
sucrose). This property makes them popular sweeteners among
diabetics and people on
low-carbohydrate diets. However, like many other incompletely digestible substances, overconsumption of sugar alcohols can lead to
bloating,
diarrhea and
flatulence because they are not absorbed in the small intestine. Some individuals experience such symptoms even in a single-serving quantity. With continued use, most people develop a degree of tolerance to sugar alcohols and no longer experience these symptoms. As an exception,
erythritol is actually absorbed in the small intestine and excreted unchanged through urine, so it has no side effects at typical levels of consumption.
The table above presents the relative sweetness and
food energy of the most widely-used sugar alcohols. Despite the variance in food energy content of sugar alcohols,
EU labeling requirements assign a blanket value of 2.4 kcal/g to all sugar alcohols.
People who have undergone
gastric bypass surgery, specifically Roux-en-Y (RGB), should be careful not to eat too many sugar alcohols as doing so, with the exception of erythritol, can lead to
“dumping”.
(Source: Wikipedia)
