CSID is an inherited condition characterized by a dysfunctional digestive enzyme.The purpose of the digestive enzyme, sucrase-isomaltase, is to break down the compound sugars sucrose (table sugar) and starch sugars so they will be small enough to be absorbed from the gastrointestinal tract.In addition to CSID, a primary gastrointestinal disorder such as a gastrointestinal infection, celiac disease or Crohn’s disease, can transiently suppress the digestive function of sucrase-isomaltase, causing an acquired form of sucrase-isomaltase deficiency (SID). Once the underlying disorder is treated and resolved, the symptoms of SID usually go away.A deficiency or absence of sucrase-isomaltase function is likely to cause chronic gastrointestinal symptoms whenever a person eats food containing sucrose or starch sugars, which are very common in carbohydrates. In fact, the sucrase-isomaltase enzyme is responsible for the digestion of all foods containing sucrose and approximately 60% to 80% of all foods containing starch sugars. When sucrose or starch sugars are not absorbed from the gastrointestinal tract, they travel to the large intestine (colon) where two things happen:
The food draws in excess water by a process called osmosis, creating watery diarrhea. The food is broken down by the normal bacteria that reside in the colon by a process called fermentation; byproducts of all fermentation include the production of excess gas and an acidic environment.The timing of gastrointestinal symptoms associated with CSID is distinctive. CSID symptoms are frequent, daily events; they are lifelong, and they are postprandial (occurring after eating food).
Diet modification
The level of ability to digest sucrose or starch sugars is unique to each person who is living with CSID and depends on many factors, including the following:
The individual level of function of the digestive enzyme sucrase-isomaltase
How well the other functions of the gastrointestinal tract are working
How much sucrose and starch sugars are consumed
If a person has any other health issues that may affect digestionFor these reasons, a restriction diet needs to be specific for each patient who has CSID. Before making any changes to the diet, it is important for a patient to speak with a healthcare provider, especially if the patient is underweight or not gaining weight as would be expected. It is also advised that the patient work with a registered dietitian or nutritionist who can help identify the foods that can be tolerated and those that cannot be tolerated. A registered dietitian or nutritionist can also help the patient plan a diet that will meet the nutritional needs for normal growth and development. Vitamins, minerals, and additional supplements may be needed to meet all nutritional needs. Epidemiology
The highest prevalence rates are seen in the Inuit populations of Greenland (5–10%), Alaska (3–7%), and Canada (about 3%). European descent prevalence ranges from 0.2% to 0.05%. There is a lower prevalence reported in African Americans and Hispanics compared to Caucasians. See also
Fructose malabsorption
Digestive system diseases
Lactose intolerance

References
External links
"Congenital sucrase-isomaltase deficiency". Genetic Home Reference. US National Library of Medicine.