Xylose is a sugar, often called “wood sugar,” that occurs naturally in a wide variety of plant life. It is classified as a monosaccharide, the simplest form of sugar, and belongs to a group of five-carbon sugars known as aldopentoses. In its purified form, xylose presents as white or colorless crystals. This sugar is a component of hemicellulose, which, along with cellulose and lignin, forms the rigid structure of plant cell walls.
Natural Sources and Properties of Xylose
Xylose is abundant in nature, primarily locked within the structure of plant-based materials. High concentrations are found in the wood of trees like birch and in agricultural byproducts such as corncobs, straw, and cottonseed hulls. It is also present in smaller quantities in various fruits and vegetables that are part of a normal diet, including raspberries, strawberries, and broccoli.
The most notable property of xylose for general comparison is its level of sweetness. It is estimated to be about 40% as sweet as sucrose, which is common table sugar. In its pure, isolated form, it appears as a white crystalline powder.
Commercial and Industrial Uses
In the food industry, xylose is used as a low-calorie sweetener and can be found in products designed for individuals managing their weight or diabetes. Its most significant industrial application, however, is serving as the primary raw material for the production of xylitol, a widely used sugar substitute. The manufacturing process involves the chemical conversion of xylose into xylitol.
Beyond food products, xylose plays a role in the field of renewable energy. As a major component of hemicellulose, it can be extracted from plant biomass and fermented by certain yeasts or bacteria. This fermentation process converts the xylose into ethanol, contributing to the production of cellulosic biofuels.
The D-Xylose Absorption Test
The D-xylose absorption test is a diagnostic medical procedure used to evaluate how well the small intestine absorbs nutrients from food. Its main purpose is to help physicians identify malabsorption disorders. The test is particularly useful in investigating the underlying causes of symptoms like chronic diarrhea, unexplained weight loss, and abdominal pain, and can be relevant in diagnosing conditions such as Celiac disease and Crohn’s disease.
The procedure for the test is straightforward. A patient is required to fast for a period before the test begins. They are then given a measured dose of D-xylose, which is dissolved in water, to drink. Following the consumption of the xylose solution, blood and/or urine samples are collected at timed intervals over the next several hours.
Xylose is the specific sugar used for this test because it is absorbed directly by the small intestine without the need for digestive enzymes. This means the amount of xylose detected in the collected blood and urine samples is a direct indicator of the small intestine’s absorptive capability. If the levels of xylose are lower than the normal range, it suggests that the intestine is not absorbing nutrients properly. Normal to high levels of xylose in the samples indicate that the intestine’s absorptive function is intact.