Polyols are carbohydrates widely utilized as sugar substitutes in food production because they provide sweetness with fewer calories than traditional sugar. These compounds are found naturally in small quantities in various fruits and vegetables, such as berries, apples, and mushrooms. They are often referred to as “sugar alcohols” in ingredient lists for diet, low-sugar, or ketogenic products. Understanding their unique chemical properties and effects on the body is relevant to modern diets.
Understanding Polyol Chemistry
A polyol is an organic compound containing multiple hydroxyl groups (-OH). These molecules are typically produced commercially by reducing the aldehyde or ketone group of a sugar molecule, such as glucose or xylose. The resulting chemical structure resembles both a sugar and an alcohol, leading to the common name “sugar alcohol.”
The “alcohol” in their name is a chemical classification and does not mean they contain ethanol. Common examples include Sorbitol, Xylitol, Maltitol, and Erythritol, each derived from a different parent sugar. The presence of multiple hydroxyl groups makes polyols water-soluble, which contributes to their functional properties in food products.
Applications in Food and Products
Polyols serve multiple purposes beyond providing sweetness. While they activate sweet taste receptors, most polyols offer less sweetness than table sugar (sucrose), often ranging from 25% to 90% of its intensity. Because they are used in high volume to achieve the desired flavor, polyols function effectively as bulking agents. This ability to add volume is necessary when sugar is removed from products like baked goods and confections, which would otherwise lack the expected texture.
Polyols also function as humectants, meaning they attract and retain moisture. This property helps keep processed foods, such as cookies and chewing gums, soft and fresh. Certain polyols, like Xylitol, are non-cariogenic, meaning they are not metabolized by the bacteria that cause tooth decay. This makes them valued ingredients in sugar-free chewing gum and dental hygiene products.
Metabolic Processing and Calorie Content
The benefit of polyols stems from their unique interaction with the digestive system. Unlike sucrose, most polyols are only partially absorbed in the small intestine. This slow absorption prevents a rapid influx of glucose into the bloodstream, resulting in a low glycemic index. This makes polyols a popular sweetener choice for individuals managing blood sugar levels, such as those with diabetes.
Incomplete absorption directly impacts their caloric value, which is lower than the four calories per gram provided by sugar. Most polyols provide between 1.5 and 3 calories per gram, often cited as 2.4 calories per gram. Erythritol is an exception; it is nearly completely absorbed in the small intestine and excreted unchanged in the urine. This unique metabolic pathway means Erythritol provides virtually zero calories, around 0.2 calories per gram.
Digestive Effects
Incomplete absorption is the mechanism that can lead to gastrointestinal side effects. The portion of the polyol not absorbed in the small intestine passes to the large intestine. There, unabsorbed polyols become a food source for resident gut bacteria, which ferment them. This fermentation produces gases, resulting in symptoms like bloating, abdominal discomfort, and flatulence.
Polyols also exert an osmotic effect as they travel through the digestive tract. They draw water into the large intestine, which softens the stool and increases bowel movements. This water-drawing action is why excessive consumption can lead to a laxative effect or diarrhea, often requiring a warning label on products. The severity of these digestive issues is dose-dependent; consuming a large amount at once increases the likelihood of discomfort.
Individuals vary in their tolerance, and those with pre-existing conditions like Irritable Bowel Syndrome (IBS) may be sensitive to small doses. Starting with small amounts and consuming polyol-containing foods with a meal can increase tolerance over time. Erythritol is generally the best tolerated polyol because its high absorption rate minimizes the amount available for fermentation in the colon.