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Sucrose Intolerance: an Overlooked Cause of Digestive Disorders
A condition more common than previously thought
Disaccharidase deficiency can be present at birth or develop later in life.
The congenital form is caused by a genetic abnormality. The best-known type is congenital sucrase-isomaltase deficiency (CSID), which reduces the ability to digest sucrose and, in some people, starches as well.
The acquired form is more common than previously thought. It can occur when the intestinal brush border is damaged—for example, due to celiac disease, Crohn’s disease, gastroenteritis, small intestinal bacterial overgrowth (SIBO), certain treatments such as chemotherapy or radiotherapy, or other conditions affecting the intestinal mucosa. The good news is that these acquired forms can sometimes improve once the underlying cause is treated and the intestine regains normal function.
How is the diagnosis made?
Diagnosis can be challenging because symptoms resemble those of several other digestive disorders, notably IBS. It is therefore based on the overall clinical picture, including symptoms, trigger foods, medical history, and the results of various tests.
Key diagnostic tools include measuring disaccharidase activity in duodenal biopsies (the gold standard), a carbon-13-labeled sucrose breath test to assess sucrose intolerance, and genetic testing for *SI* gene variants when a congenital form is suspected.
It is important to emphasize that no test is perfect. Results must always be interpreted in the context of symptoms and the overall clinical picture. An enzyme deficiency detected in the laboratory is not always the cause of the symptoms, just as a person may exhibit consistent symptoms despite inconclusive test results. For this reason, a comprehensive assessment by a gastroenterologist or a dietitian experienced in this condition remains essential.
Another approach sometimes suggested is the “4-4-4” sucrose home test. This involves dissolving 4 tablespoons (approximately 50 g) of table sugar in 4 ounces (120 mL) of water, drinking the solution on an empty stomach, and then monitoring for the onset of digestive symptoms over the next 4 to 8 hours. Although this test may provide useful clues for some individuals, it has not yet been validated by clinical studies and cannot establish a diagnosis on its own. Results should always be interpreted with caution and discussed with a healthcare professional.
Author
Kathryn holds a Bachelor Degree in Nutrition as well as a Bachelor and a Master Degree in Kinesiology, all from Laval University. She is a Registered Dietitian and active member of the Ordre professionnel des Diététistes Nutritionnistes du Québec (ODNQ) and of the American Academy of Nutrition and Dietetics. She holds the Monash University's certification for the FODMAP diet and IBS, and has considerable clinical experience in that area. She is also an accomplished athlete, having ran track and cross-country at a national level. Kathryn specializes in sports nutrition, weight loss, diabetes, as well as heart and gastrointestinal health.
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