why does my gut gurgle?

Could it be sucrose intolerance or SIBO?

Have you ever had a bubbling belly or sour stomach after eating a meal?

Does it happen enough that you are concerned and are thinking about seeing a gastroenterologist? The goal of the gastroenterologist is to find out what’s causing your symptoms, so that the problem can be fixed instead of having you just manage the symptoms.

Sucrose intolerance and small intestinal bacterial overgrowth (SIBO) are two of the problems doctors are looking for. The symptoms for both are similar and include gas, bloating, cramping, abdominal pain, diarrhea, and fatigue. So how does the doctor know which problem to fix? Let’s compare what we know about each disorder.

Sucrose Intolerance

Sucrose intolerance, sometimes referred to as congenital sucrase-isomaltase deficiency (CSID), is a genetic enzyme deficiency that results in undigested sucrose and starch passing into the large intestine where the bacteria work on fermenting it, causing the symptoms you experience.

Two methods are used to help the doctor find out if a person has enough sucrase to properly digest their food. The gold standard test is a disaccharidase assay biopsy, a procedure where a small piece of tissue is biopsied from the small intestine and sent to a lab for enzyme activity studies. The second is a breath test. Two types of breath tests are available; one measures hydrogen and methane in the breath and another uses a stable isotope of carbon to show enzyme activity. Both breath tests can be performed in the comfort of your home and may be able to help doctors determine if you have sucrose intolerance.


SIBO is a different problem. Bacteria are plentiful in the large intestine and they are critical for good health. But when they move up into the small intestine, problems can arise. SIBO can be identified through a duodenal aspirate (taking a fluid sample and counting the colonizing units) and also through a breath test that identifies fermentation of a carbohydrate that should not be fermented until reaching the large intestine. Since SIBO can occur when digestive enzymes do not do their job completely, it is important to consider the cause so once the bacteria are treated the problem is corrected and SIBO doesn’t return.

Being aware of your symptoms and when they first started is important to help your doctor decide what to look for first. Sucrose intolerance is a problem that may have lasted for years while SIBO may be a more recent development. Having a belly ache after a high-sugar meal might happen with both; however, if the sugar source is actually high-fructose corn syrup, that may be a SIBO signal. Keeping a food and symptom journal is a good idea any time the gurgling gut is getting you down and may be really helpful in getting to the reasons behind it.