Allulose is a low-calorie sweetener that has gained popularity as a substitute for traditional table sugar, offering a similar taste and texture with minimal caloric impact. Classified as a rare sugar, allulose is a monosaccharide, or single-unit sugar, naturally found in small quantities in foods like figs and raisins. It is produced commercially from corn or fructose to meet market demands. People are curious about how this unique sugar affects the body, particularly the digestive tract.
How the Body Processes Allulose
The unique structure of allulose dictates how it is processed differently from other sugars. When consumed, allulose is mostly absorbed directly into the bloodstream from the small intestine, but the human body lacks the necessary enzymes to fully metabolize it for energy. Approximately 70% of the absorbed allulose is then excreted quickly and unchanged through the urine. This efficient, non-metabolized pathway is the reason for its nearly negligible caloric value (0.2 to 0.4 calories per gram), and it does not significantly raise blood sugar or insulin levels. About 30% of the ingested allulose is not absorbed in the small intestine and continues its journey into the large intestine, where this unabsorbed portion interacts with the gut environment, leading to the potential for digestive symptoms.
Digestive Tolerance and Acute Side Effects
The unabsorbed allulose reaching the large intestine can cause acute physical symptoms related to its concentration. When unabsorbed, it creates an osmotic effect, pulling excess water into the intestinal tract. This increased fluid volume can result in loose stools or diarrhea, particularly when large quantities are consumed. Discomfort is highly dose-dependent, meaning the amount consumed directly influences the likelihood and severity of side effects. Studies have established specific thresholds for consumption.
For healthy adults, the suggested maximum single dose to avoid significant gastrointestinal symptoms is about 0.4 grams per kilogram of body weight. Exceeding this limit can significantly increase the risk of severe diarrhea and abdominal pain. The suggested maximum total daily intake is higher, at about 0.9 grams per kilogram of body weight, allowing for consumption over the course of a day. This individual tolerance explains why some people can consume allulose without issue, while others experience gas, bloating, or abdominal pain. These symptoms arise because the unabsorbed sugar becomes available for fermentation by bacteria in the colon, which produces gas as a byproduct, so starting with small amounts allows the body to adjust and helps determine personal tolerance.
Allulose’s Interaction with Gut Bacteria
The portion of allulose that bypasses absorption in the small intestine ultimately enters the large intestine, where it encounters the vast community of gut bacteria. Once in the colon, this unabsorbed sugar is fermented by certain microbes. This fermentation process is what can lead to the production of gas, contributing to symptoms like bloating. However, this interaction also introduces the possibility of allulose acting as a mild prebiotic. Prebiotics are non-digestible food components that selectively stimulate the growth or activity of beneficial bacteria in the gut.
Some research suggests that allulose consumption may promote the growth of specific beneficial bacteria, such as Bifidobacterium and Akkermansia. These changes in microbial activity and composition are a key area of ongoing research. While the fermentation can cause acute discomfort, the long-term impact on the overall gut microbiome appears to be minimal and potentially positive. Current evidence suggests that allulose does not cause significant negative disruption to a healthy gut microbial community.