Sugar intolerance refers to a digestive condition where the body is unable to properly break down and absorb specific types of sugar, or carbohydrates, in the small intestine. This difficulty is most often traced back to a deficiency or reduced activity of certain digestive enzymes responsible for breaking down complex sugars. For instance, lactose intolerance results from insufficient production of the enzyme lactase, which is required to digest the sugar found in dairy products. When these sugars are not digested and absorbed efficiently, they pass into the large intestine, causing symptoms. Sugar malabsorption can affect various sugars, including lactose, fructose, and sucrose, leading to gastrointestinal distress.
Common Indicators of Intolerance
The inability to fully digest certain sugars triggers symptoms in the gastrointestinal tract, often prompting individuals to seek medical testing. These indicators typically begin shortly after consuming the offending food, ranging from minutes to a few hours after ingestion. Common symptoms include abdominal pain, bloating, and flatulence caused by fermentation in the colon.
Changes in bowel habits, such as diarrhea or, less commonly, constipation, are also frequent complaints, along with feelings of nausea or stomach rumbling. It is important to distinguish these digestive symptoms from a true food allergy. An allergy involves an immune system response and can cause reactions like hives or difficulty breathing, whereas intolerance is a digestive issue related to enzyme function.
Understanding the Hydrogen Breath Test
The Hydrogen Breath Test (HBT) is the standard, non-invasive method used to diagnose the malabsorption of specific sugars, such as lactose or fructose. The test relies on the fact that only bacteria in the large intestine produce hydrogen or methane gas. When a sugar is not properly digested in the small intestine due to enzyme deficiency, it travels undigested into the colon.
There, resident bacteria rapidly ferment the sugar, producing hydrogen and methane gases as byproducts. These gases are absorbed into the bloodstream, travel to the lungs, and are exhaled in the breath. The test measures the concentration of these gases in the person’s breath over a period of two to three hours.
The procedure begins with a baseline breath sample, followed by the consumption of a specific sugar solution, such as a measured dose of lactose or fructose mixed with water. Subsequent breath samples are collected every 15 to 30 minutes. A significant rise in hydrogen or methane levels above the baseline indicates malabsorption of the tested sugar. Clinicians consider a rise of more than 20 parts per million (ppm) of hydrogen a positive result for malabsorption.
Accurate test results require specific patient preparation to prevent false readings:
- Patients must avoid antibiotics and certain medications, such as Pepto-Bismol, for up to two weeks before the test.
- A specialized low-carbohydrate, low-fiber diet is often required for the two days prior to the test to reduce gas-producing food residues.
- An overnight fast of eight to twelve hours is mandatory on the day of the test.
- Patients must avoid smoking, gum, and intense physical activity during the testing period.
Other Diagnostic Approaches
While the Hydrogen Breath Test is widely used for common intolerances, other diagnostic methods are available, particularly when the breath test is inconclusive or for investigating rarer conditions. One approach is the Blood Glucose Test, also known as the Oral Tolerance Test. In this test, a blood sample is taken before and at set intervals after the patient ingests the specific sugar solution.
If the sugar is properly digested and absorbed, blood glucose levels will rise significantly. Conversely, malabsorption results in a minimal rise, often less than 20 milligrams per deciliter, indicating the sugar was not absorbed. This method is less common now due to the invasiveness of repeated blood draws, but it provides a direct measure of absorption.
For complex enzyme deficiencies, such as congenital sucrase-isomaltase deficiency, an Intestinal Biopsy is used. This invasive procedure involves using an endoscope to collect a small tissue sample from the small intestine lining. The sample is then analyzed to directly measure the activity of specific enzymes, providing definitive proof of a deficiency. An Elimination and Reintroduction Diet can also serve as a preliminary or confirmatory step by removing the suspected sugar and then reintroducing it to observe symptom return.
Life After Diagnosis
Receiving a confirmed diagnosis of sugar intolerance is the first step toward effective symptom management and improved quality of life. The focus shifts to implementing dietary modifications that limit or exclude the problematic sugar. This often involves strict avoidance of the identified carbohydrate, such as restricting lactose-containing dairy products or following a low-FODMAP diet if fructose is the issue.
The level of restriction needed varies greatly, as some individuals can tolerate small amounts of the sugar without discomfort. In addition to dietary adjustments, enzyme supplements are a common management tool. For example, individuals with lactose intolerance can take a lactase enzyme tablet immediately before consuming dairy to help break down the sugar. For rarer deficiencies, like sucrase-isomaltase deficiency, prescription enzyme replacement therapies are available to aid digestion.