Sucrose intolerance is a condition where the body has difficulty breaking down sucrose due to a deficiency of the sucrase-isomaltase enzyme in the small intestine. When sucrose is not broken down effectively, it can lead to digestive symptoms.
The Mechanism of Sucrose Intolerance
Sucrose, commonly known as table sugar, is a disaccharide, meaning it is composed of two simpler sugar units: glucose and fructose. For absorption, sucrose must be broken down into these monosaccharide components. This occurs in the small intestine, where the sucrase-isomaltase enzyme catalyzes its hydrolysis into absorbable glucose and fructose.
When the sucrase-isomaltase enzyme is deficient, undigested sucrose cannot be absorbed. Instead, it travels to the large intestine. There, gut bacteria ferment the sucrose, producing gases and other byproducts. This fermentation leads to uncomfortable digestive symptoms.
Sucrose intolerance primarily manifests in two forms. Congenital Sucrase-Isomaltase Deficiency (CSID) is a genetic disorder where individuals are born with a reduced or absent ability to produce functional sucrase-isomaltase enzyme due to gene mutations. This inherited condition typically presents in infancy or early childhood when sucrose or starch-containing foods are introduced into the diet.
The other form, acquired (secondary) sucrose intolerance, develops later in life due to damage or injury to the small intestine’s lining, which impairs the production of the sucrase-isomaltase enzyme. Conditions like celiac disease, small intestinal bacterial overgrowth (SIBO), or inflammatory bowel disease can contribute to this type of intolerance. Once the underlying cause is addressed, symptoms of acquired sucrose intolerance may resolve.
Identifying the Symptoms
Symptoms of sucrose intolerance primarily involve the digestive system and often appear shortly after consuming sucrose. These include abdominal pain, cramping, and bloating. These symptoms arise from the fermentation of undigested sucrose by bacteria in the large intestine, which produces excess gas.
Individuals may also experience increased gas, flatulence, and nausea. Diarrhea, which can be chronic, watery, and acidic, is another frequent symptom. Vomiting or a feeling of fullness after eating can also occur.
The severity of symptoms varies among individuals, depending on the amount of sucrose consumed and the degree of enzyme deficiency. While digestive discomfort is the most prominent sign, some individuals might also experience non-digestive symptoms such as fatigue and headaches.
How Sucrose Intolerance Is Diagnosed
Diagnosing sucrose intolerance typically begins with a review of symptoms and dietary history. Medical professionals inquire about foods consumed and any resulting digestive discomfort. This assessment helps determine if sucrose might be a trigger.
The hydrogen breath test is a common diagnostic method, which is a non-invasive procedure. After consuming a controlled sucrose solution, breath samples are collected over several hours. The test measures hydrogen and/or methane gases in exhaled breath. Elevated levels indicate undigested sucrose fermentation by bacteria in the large intestine.
While the hydrogen breath test is a common screening tool, it is not always definitive for confirming a diagnosis of Congenital Sucrase-Isomaltase Deficiency (CSID). An intestinal biopsy, where a tissue sample is taken from the small intestine during endoscopy, can directly measure sucrase-isomaltase enzyme activity. Genetic testing can also identify mutations in the SI gene associated with CSID, confirming the inherited form.
Living with Sucrose Intolerance
Managing sucrose intolerance primarily involves dietary adjustments to limit or avoid high-sucrose foods. This means reducing or eliminating table sugar and many processed foods. Individuals should read food labels, as sucrose can be hidden in products like sauces, dressings, and baked goods, often listed as “sugar” or “cane sugar.”
Certain fruits and vegetables naturally contain sucrose, and their consumption may need to be limited depending on individual tolerance. Examples of typically lower-sucrose fruits include berries, citrus fruits, and avocados. Lean proteins like chicken, fish, and eggs, along with whole grains such as oats, quinoa, and rice, are usually safe options.
Enzyme replacement therapy is another management option. Prescription enzyme supplements, such as sacrosidase, help break down sucrose during digestion, reducing symptoms and potentially allowing for a less restrictive diet.
Consulting with healthcare professionals, particularly a dietitian, is highly recommended. A dietitian can provide personalized dietary advice, help identify food triggers, and ensure nutritional needs are met while managing sucrose intake. They can also guide individuals in slowly reintroducing foods to determine personal tolerance levels.