Starch intolerance

Sucrose, maltose and starch intolerance

Starch intolerance


Individuals with congenital sucrase-isomaltase enzyme deficiency (CSID or GSID) have reduced digestion of the sugars sucrose (table sugar) and maltose (found in grains) and sometimes also of starch in the small intestine.

The deficiency may affect several enzymes (sucrose, maltase, isomaltase and lactase), is caused by multiple possible genetic mutations and is therefore present from birth onwards. Depending on the mutation, sucrose, maltose, starch and sometimes also lactose digestion are impaired, leading to varying degrees of intolerance of these carbohydrates. The intolerance symptoms are caused by a reduced breakdown in the small intestine and subsequent fermentation by the flora (microbiome) in the lower intestine.

Inheritance is by an autosomal recessive pattern, i.e. both parents must have the mutation for the child to develop the full-blown disease. The parents (heterozygotes) typically show no or only minor signs and symptoms of the condition.

Frequency in population and natural history

The frequency of classic sucrose-isomaltase deficiency is estimated to be 1 in 5000 people of European descent. In native populations of Greenland, Alaska, and Canada up to 1 in 10 individuals may be affected.

In children with chronic diarrhea of unknown origin 4-10% have CSID. 1 in 1000 adults with chronic diarrhea are likely to have some degree of CSID.

Between 2 and 9% of the general US population are carriers of the genetic abnormality (heterozygotes), some of whom are likely to have symptoms similar to Irritable Bowel Syndrome.

Congenital sucrase-isomaltase deficiency usually becomes symptomatic after an infant is weaned and starts to ingest fruits, juices, and grains. Children may tolerate sucrose and maltose better as they get older. However, the condition often persists and rarely only appears in adulthood. If the diet is restricted appropriately affected individuals live normal lives.


The ingestion of sucrose, maltose or starch (and sometimes also lactose) typically results in stomach cramps, bloating, excess gas production, nausea, vomiting and diarrhea. These digestive problems can lead to lower than normal weight gain and growth. Depending on the type of CSID, varying amounts of sucrose, maltose, starch or lactose are tolerated. Upper respiratory tract, ear and viral infections are common and kidney stones and copper malabsorption may be more frequent.

Testing and diagnosis

Genetic analysis or enzyme activity determination in small intestinal biopsies during endoscopy and the C13-sucrose breath test are the most accurate diagnostic tools.

Sucrose breath hydrogen breath tests are simple and useful, but less accurate. Careful history taking and observation of food-related reactions may indicate the source of food intolerance. 

The food history should include:

  • Identification of suspect food, drink, sweets / candy, or chewing gum.
  • What is the time lag between eating and development of symptoms?
  • What types of symptoms ensue?
  • What amount of food is required to cause reaction?
  • Does the reaction occur with every ingestion of the food?
  • Does the reaction only occur under certain circumstances, e.g. exercise or stress?
  • When did the last reaction occur?
  • Do allergies exist, e.g. hay fever, asthma, eczema?
  • Do other family members have food reactions, if so, which?

Breath tests

Breath tests are the most useful and non-invasive tests for determining the various sugar (e.g. fructose, lactose, sucrose) and sugar alcohol (e.g. sorbitol, xylitol) intolerances. They are well validated, widely used, but some discussion still exists about the ideal test conditions. These tests should not be used in infants and reduced doses of test compound are used in children. The tests procedures are identical for all the intolerances.

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Contact us if you have problems accessing tests locally.

The following are important details regarding the test procedure:

  • Dietary restrictions, no smoking or excessive exercise from the day before testing and no antibiotics or colonoscopy in the last week pre-test.
  • Ingestion of a specific amount of the sugar or sugar alcohol to be tested for intolerance.
  • Regular breath samples taken for a standardized period.
  • Diary of symptoms during the next day for calculation of the symptom index.
  • Measurement of specific gases, e.g. hydrogen and methane, in the breath samples.

An intolerance is diagnosed based on the symptoms following the test and the gas concentrations in the breath samples. The diagnosis is confirmed by a significant decrease in symptoms whilst on a diet low in the poorly tolerated sugar or sugar alcohol. Expert dietary advice is very helpful for the identification of food and drink containing the difficult-to-spot offending ingredient.

See Food tables

Direct enzyme quantification in tissue biopsies

Direct enzyme levels can be determined in biopsies of the small intestine. Only a few laboratories can perform these complex analyses. Sucrase-isomaltase deficiency, a quite rare genetic disorder, is preferentially diagnosed using this method.

Genetic tests

Sucrase-isomaltase deficiency (sucrose – starch intolerance): genetic analysis from duodenal biopsies is not widely available, but has demonstrated several genetic polymorphisms, i.e. abnormalities.


Reduction and sometimes strict avoidance of sucrose and maltose intake is required.

This means avoiding table sugar in all forms, such as sugar cane and sugar beets, sorghum, confectioners’ sugar or powdered sugar, rock candy, brown sugar (made of white sugar and molasses), cotton candy, maple syrup, Demerara and Barbados sugar, molasses, pancake syrup, gingerbreads, baked beans and pumpernickel breads. In some affected individuals sources of starch need to be avoided as well.

Sacrosidase (Sucraid®) is the appropriate oral enzyme replacement

( for sucrose digestion, but does not aid in the digestion of maltose or starch.

See Food tables for a listing of sucrose, starch and maltose content in food

Links to literature

CSID Food Composition Tables CSID cares Sucraid

Symposium review papers on sucrose-isomaltase deficiency from the 8th Starch Digestion Consortium Workshop in the JPGN 2012;55:Supplement 2 (PDFs)

Clinical Aspects and Treatment of Congenital Sucrase- Isomaltase Deficiency

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Congenital Sucrase-Isomaltase Deficiency: Heterogeneity of Inheritance, Trafficking, and Function of an Intestinal Enzyme Complex

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Congenital Sucrase-Isomaltase Deficiency: Summary of an Evaluation in One Family

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Direct Starch Digestion by Sucrase-Isomaltase and Maltase-Glucoamylase

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Four Mutations in the SI Gene Are Responsible for the Majority of Clinical Symptoms of CSID

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Frequency of Sucrase Deficiency in Mucosal Biopsies

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Starch Digestion and Patients With Congenital Sucrase-Isomaltase Deficiency

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Transient Sucrose and Starch Intolerance

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