Sugar intolerance is a digestive issue where the body struggles to properly break down and absorb specific carbohydrate molecules. Unlike a food allergy, which involves an immune system response, intolerance is a non-immune reaction rooted in the digestive tract. When the body cannot process a sugar correctly, the substance travels to the large intestine, causing uncomfortable symptoms. Treatment primarily focuses on managing these symptoms through diet and, in some cases, supplemental enzymes.
Defining the Root Cause of Intolerance
Sugar intolerance results from a deficiency or absence of specific digestive enzymes in the small intestine. These enzymes are necessary to break down complex sugars (disaccharides) into simple sugars (monosaccharides) that the body can absorb. Without proper enzyme activity, the undigested sugar remains in the gut, pulling water into the intestines and causing diarrhea.
The most common types of sugar intolerance stem from a different missing enzyme. Lactose intolerance, the most frequent, is caused by a shortage of lactase, which breaks down milk sugar (lactose). Sucrose intolerance, also known as Congenital Sucrase-Isomaltase Deficiency (CSID), occurs when the sucrase-isomaltase enzyme is deficient, preventing the breakdown of table sugar (sucrose) and starches. Fructose malabsorption involves difficulty absorbing fruit sugar (fructose), often related to transporter proteins rather than an enzyme deficiency.
Confirming the Diagnosis
Identifying the specific sugar causing digestive distress requires professional medical testing. A definitive diagnosis allows for targeted treatment and avoids unnecessarily restrictive diets. The most common tool used to identify carbohydrate malabsorption is the Hydrogen Breath Test.
This non-invasive test involves the patient ingesting a measured amount of the sugar being tested, such as lactose or fructose. If the sugar is not digested, it ferments in the colon, producing hydrogen gas. This hydrogen travels to the lungs and is exhaled, where a machine measures the levels in the breath over two to four hours. For rare conditions like CSID, a medically supervised elimination diet or a small intestine biopsy to measure enzyme activity may be necessary.
Primary Treatment: Dietary Restriction and Management
The primary strategy for managing sugar intolerance is careful dietary restriction of the specific trigger sugar. The initial step is often a medically supervised, short-term elimination diet to confirm that removing the sugar resolves the symptoms. Once the trigger is identified, long-term management focuses on sustained avoidance while maintaining nutritional balance.
Learning to read food labels is essential, as the trigger sugar can be disguised under multiple names. For example, individuals with sucrose intolerance must look for “sucrose,” “table sugar,” or “cane sugar” on ingredient lists. Similarly, fructose can be hidden in ingredients like high-fructose corn syrup, honey, and agave nectar. Many packaged goods, condiments, and even savory items contain added sugars.
Successful management involves substituting foods containing the problematic sugar with tolerable alternatives. For lactose intolerance, alternatives include plant-based milks and aged cheeses, which are naturally lower in lactose. For fructose malabsorption, substituting high-fructose fruits like apples and pears with lower-fructose options such as berries or citrus fruits can help. A critical aspect is recognizing that many individuals have a tolerance threshold, meaning they can consume a small amount of the sugar without symptoms. Determining this unique threshold requires careful, self-monitored experimentation.
Using Enzyme Replacement Therapies
Enzyme replacement therapies offer a secondary medical approach to manage symptoms when dietary restrictions are challenging. These supplements introduce the missing enzyme directly to the digestive tract to assist in breaking down the problematic sugar. The most widely available example is over-the-counter lactase supplements, taken immediately before consuming dairy products to help digest lactose.
For other intolerances, specific enzyme supplements are available, sometimes requiring a prescription. For instance, individuals with CSID may be prescribed a saccharomyces cerevisiae-based product containing sucrase to help break down sucrose. These supplements are generally taken at the start of a meal containing the trigger food to ensure the enzyme is present simultaneously with the sugar. While enzyme therapy improves quality of life and dietary flexibility, it does not cure the underlying condition or eliminate the need for some dietary caution.