The confusion surrounding carbohydrate counting often arises for individuals following low-carb or ketogenic diets when they consume alternative sweeteners. Standard nutrition labels can be misleading because they group all types of carbohydrates together, regardless of how the body processes them. This presents a dilemma for dieters trying to calculate their true carbohydrate intake, especially with ingredients the body does not fully break down for energy. Understanding how a specific sweetener, like allulose, is listed and metabolized is necessary for accurately tracking dietary macros.
Defining Allulose: A Rare Sugar
Allulose is chemically classified as a “rare sugar,” a monosaccharide that occurs naturally in only small amounts in certain foods. Its chemical name is D-psicose, and it shares the same molecular formula as fructose, though its atoms are arranged differently. Trace amounts can be found in wheat, figs, raisins, and maple syrup. Commercially, it is often produced through enzymatic conversion from corn or fructose.
This sweetener provides a taste and texture similar to traditional table sugar (sucrose), though allulose is only about 70% as sweet. In the US, allulose has been granted Generally Recognized As Safe (GRAS) status by the Food and Drug Administration, permitting its use as a sugar substitute.
The Net Carb Calculation for Allulose
The concept of “net carbs” is used by dieters to estimate the carbohydrates that actually affect blood sugar levels, excluding those the body cannot digest or metabolize for energy. The calculation involves subtracting non-digestible components, such as fiber and certain sweeteners, from the total carbohydrate count. Allulose belongs in this category due to its unique metabolic pathway. When a product contains allulose, the total grams of allulose should be subtracted from the total carbohydrates listed on the nutrition label to determine the net carbohydrate count. For example, if a product lists 15 grams of Total Carbohydrate and 10 grams of Allulose, the net carb count is 5 grams (15 – 10 = 5).
The United States Food and Drug Administration requires allulose to be included in the “Total Carbohydrate” count on the Nutrition Facts panel because it is technically a carbohydrate. However, the agency permits it to be excluded from the “Total Sugars” and “Added Sugars” lines, reflecting its minimal metabolic impact. Manufacturers often list allulose separately on the label, which simplifies the net carb calculation for consumers.
How Allulose is Metabolized (or Not)
The subtraction rule for allulose is based entirely on its distinct physiological fate within the human body. Unlike common sugars like glucose, which the body readily uses for fuel, allulose is largely ignored by metabolic pathways. After ingestion, a significant portion, estimated to be between 70% and 90%, is absorbed from the small intestine into the bloodstream. Despite being absorbed, the body lacks the necessary enzymes to effectively metabolize allulose for energy. Consequently, it circulates briefly before being excreted almost entirely unchanged in the urine.
Studies show that over 80% of an ingested dose leaves the body via the urine, demonstrating a lack of energy conversion. This inefficient metabolism results in a negligible caloric contribution, ranging from approximately 0.2 to 0.4 calories per gram. This is in stark contrast to standard table sugar, which provides about 4 calories per gram because it is fully metabolized.
Allulose and Your Diet Goals
The unique metabolic properties of allulose make it highly compatible with diet goals focused on carbohydrate restriction and blood sugar management. Allulose has a Glycemic Index (GI) of virtually zero, meaning consuming products containing it does not cause a rapid or significant increase in blood glucose levels. Allulose also does not trigger a major insulin response, which benefits individuals managing diabetes or seeking to maintain ketosis. Traditional sugars cause a sharp rise in blood sugar, prompting an insulin release that can halt the body’s fat-burning process. Allulose bypasses this mechanism, allowing the body to continue utilizing fat for fuel.
Because of its minimal impact on blood sugar and insulin, it is widely considered a keto-friendly sweetener. Subtracting the allulose content ensures dieters are only counting the carbohydrates that could potentially interfere with their metabolic state.