Sucrose (table sugar) Intolerance is more common than you think! Your unresolved enteropathy IBS-D/M (irritable bowel syndrome-diarrhea/mixed) symptoms discussed in Article 3 may actually be caused by Sucrose Intolerance.
Let’s summarize the articles in the series that are relative to this possibility. If you haven’t already done so, we recommend you begin by reviewing the two introductory articles of the enteropathy series:
In this series, we’re empowering you to:
- Initially consider your triad of gut symptoms to be those of an enteropathy other than IBS (Article 3): abdominal pain and/or discomfort, gas (abdominal bloating, distention, flatulence, and/or gurgling — rumbling), and bowel dysfunction with constipation, diarrhea, or both. In this article, we’re focusing on bowel dysfunction that includes loose stools and diarrhea.
- Know your differential diagnosis, which is consideration of all possibilities that may be either causing or contributing to your enteropathy symptoms (Article 4). Importantly, Sucrose Intolerance is a relatively common one.
- Understand how and why eating certain foods may trigger enteropathy symptoms (Article 5).
Don’t accept an initial diagnosis of IBS without considering the differential diagnosis of possible causes. Figure 6.1 is a simplification of my map of differential diagnoses introduced as Figure 4.1 in Article 4.
The circled numbers have been removed with the exception of #6, which includes common, specific food-related enteropathies. Recalling the learning in (Article 5), we refer to both maldigestion and malabsorption collectively as malabsorption.
The red oval emphasizes the need to consider the diagnosis of Sucrose Intolerance. Remember, it’s possible for more than one diagnosis or disorder to be present.
Sucrose Intolerance/malabsorption refers to the inability or reduced ability to digest sucrose (table sugar) in the small intestine. Sucrase is an enzyme located in the small intestinal lining that is responsible for digestion of the sugar, sucrose. Sucrose Intolerance is caused by either the absence or reduced activity of sucrase, resulting in diminished digestion, colonic fermentation, and enteropathy symptoms after eating foods containing sucrose, as shown in Figure 6.2.
Figure 6.2 is a cut-away side view of the gut. Note the arrow pointing to the horizontal blue line marking the transition of the small intestine above and the colon or large intestine below. The figure shows the difference between a normal intestine on the left, where the sucrase digestive enzyme is present, versus an intestine on the right that has either absent or reduced activity of the sucrase enzyme. Without this enzyme, intestinal gases are produced when food containing sucrose is fermented by the normal bacteria present in the colon, as well as excess water in the colon that is drawn in by the presence of other undigested molecules. Symptoms of enteropathy result. If SIBO (small intestinal bacterial overgrowth) is present, fermentation can also occur in the small intestine.
Causes of Sucrose Intolerance
Just as there are many causes of enteropathy, there are also many causes of Sucrose Intolerance:
- Congenital or genetic Sucrose Intolerance, first symptomatic in infancy or early childhood – This relatively rare condition is also called Congenital Sucrase-Isomaltase Deficiency (CSID). It’s a genetic disorder in which the infant inherits two variants of the gene that codes for sucrase-isomaltase, one from each parent, who may or may not have symptoms of Sucrose Intolerance. Symptoms of Sucrose Intolerance may be severe, resulting in chronic malnutrition and failure to thrive. Because it is a genetic disorder, CSID is a life-long condition.
- Later onset and/or diagnosis – Research confirms up to 5 percent — that’s five in 100 — who have the enteropathy symptoms described here or have otherwise been diagnosed with IBS-D/M may instead have CSID. Sucrose Intolerance may also coexist with other diagnoses.
- SIBO (small intestinal bacterial overgrowth) – Refer to Article 4, Figure 4.1, and #2a. The presence of colon-type bacteria in the small intestine can result in fermentation of sucrose before it gets down to the colon. It’s important to search for the underlying cause or causes of SIBO. If corrected, this acquired form of Sucrose Intolerance may be relieved.
- Multiple diseases and disorders – Irritation or inflammation of the intestinal lining commonly occur with some enteropathies, which can result in the development of either deficient or malfunctioning digestive enzymes, including sucrase-isomaltase. Examples of these enteropathies include celiac disease, Crohn’s disease, or gut infection, which may develop at any age. If the underlying enteropathy can be successfully treated and the intestinal irritation and inflammation resolved, the acquired Sucrose Intolerance may improve or resolve.
Diagnosis of Sucrose Intolerance
Several methods are available that can aid in the diagnosis of Sucrose Intolerance.
Gastrointestinal Endoscopy Test
During a gastrointestinal endoscopy test, several biopsies (tissue specimens) may be obtained from the small intestinal wall and sent for a specialized analysis of enzymatic activity of a number of disaccharide enzymes, including sucrase and isomaltase. The laboratory analysis that determines enzyme activity is commonly known as a disaccharidase assay via a small bowel biopsy. After measuring the activity of these intestinal disaccharidases (lactase, sucrase, isomaltase or palatinase, and maltase), a definitive diagnosis of the presence or absence of CSID can be made.
Sucrose Breath Testing
NOTE: Sucrose Hydrogen/Methane breath testing was discussed in Article 4.
13C-Sucrose Breath Test
The 13C-Sucrose Breath Test is a simple, non-invasive breath test that quantifies sucrase activity. The test uses a sucrose solution containing naturally occurring 13C as the test nutrient. Sucrose is broken down by sucrase, which splits 13C-sucrose into 13C-glucose and 13C-fructose. These simple sugars are absorbed through the intestinal mucosal cells and metabolized in the liver, releasing 13CO2, which is transported by the blood to the lungs where it is expelled in the breath. The amount of 13CO2 in exhaled breath correlates with the amount of sucrase activity in the small intestine. Note that people with sucrase deficiency may experience gastrointestinal symptoms following the consumption of the sucrose required as the test nutrient.
Sugar Challenge Test
The 4-4-4 Sugar Challenge Test is a simple, short test that can be performed by the individual at home. A physician should be consulted before this test is performed. Stir 4 tablespoons of table sugar into 4 ounces of water and drink it on an empty stomach. If symptoms (bloating, gas, and/or diarrhea) occur during the next 4 to 8 hours, this is suggestive of decreased sucrase activity. Please consult your doctor before taking this test. This test is not appropriate for infants, young children, geriatric patients, and those with comorbid conditions such as diabetes. Individuals may have severe symptoms if they are very sensitive to sugar.
Treatment of Sucrose Intolerance
When Sucrose Intolerance is caused by the genetic condition CSID, the GI symptoms may be managed with a restriction diet, pharmaceutical therapy, or both. People with Sucrose Intolerance, whether acquired or genetic, may have individual tolerances for foods containing sucrose or other carbohydrates such as starches. For this reason, no one restriction diet is appropriate for all individuals. People with Sucrose Intolerance should work with their doctor and/or a registered dietitian to develop a diet that they can tolerate and still consume the nutrients they need.
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