The scientific name for “table sugar” is sucrose, and it’s also found in maple syrup, many fruits and vegetables, and is commonly added to beverages and foods. If you can’t properly digest sucrose, you might have the disorder known as sucrose intolerance. Clinicians may also call it sucrase-isomaltase deficiency (SID) — as we will in this report — or congenital sucrase-isomaltase deficiency ( CSID). While not common, neither is this disorder extremely rare. Sucrose intolerance can lead to a range of chronic digestive symptoms, some mimicking irritable bowel syndrome (IBS). Diagnosing and treating sucrose intolerance typically involves certain tests and procedures conducted by a gastroenterologist. Some adults learn to live with the disorder, if symptoms are mild, without medical treatment, by trying to limit their sucrose intake — which can benefit your metabolic health (glycemic management, especially). 

Who gets sucrose intolerance?

The inability to digest sucrose properly usually results from genetics, so SID often occurs first in infancy, after the baby starts ingesting sucrose- and starch-containing foods (such as fruit juices, solid foods, common baby foods, milk-based formula, and medications sweetened with sucrose). While the condition can be “managed,” there really is no definitive cure, and so it can persist throughout adulthood. 

SID can also result from inflammation or infection of the small intestine.

Whether the cause is genetics or an intestinal injury/infection/disorder, SID results because of an inadequate supply of an important enzyme, sucrase isomaltase. 

While it’s long been considered a fairly uncommon disorder — and far less prevalent than, say, celiac disease or lactose intolerance, a recent clinical study found that 35% of patients with presumed IBS-D/M actually had SID. Consequently, SID is increasingly being considered in the differential diagnosis of patients presenting with abdominal pain, diarrhea, or bloating.

What are the symptoms of sucrose intolerance?

Without enough of the sucrase isomaltase enzyme, the sucrose you eat is not well absorbed and passes into the colon, where intestinal bacteria digest it — often resulting in bloating, gas, and abdominal discomfort.

More severe, but rare symptoms can include chronic diarrhea, weight loss, frequent bowel movements, abdominal distention, and vomiting.

How do you test for sucrose intolerance?

Following a detailed clinical history and exam, if sucrose intolerance is the suspected cause of the gastrointestinal discomfort, a physician (most typically a gastroenterologist) can order a 13C-sucrose breath test, which determines the amount of sucrase isomaltase enzyme activity you have. Another way to diagnose sucrose intolerance is by taking biopsies (tissue samples) of the small intestine during endoscopy. While this is more invasive than breath testing, it has the added advantage of measuring enzyme activity for sucrase isomaltase as well as other digestive enzymes produced in the same region, including lactase (to digest milk sugar) and maltase (to digest starches). 

How do you treat sucrose intolerance?

There is no cure for SID, but it can be managed. If you have received a sucrose intolerance diagnosis, you will likely be treated through some combination of a supplemental enzyme use and diet change. A prescription enzyme is available and can help you comfortably tolerate sucrose-containing foods when dosed properly before a meal. (January AI does not endorse companies or products; talk with your medical provider for more information.) However, this medication is not always completely effective, especially if the timing of its use is inconsistent; therefore, dietary management is also key — which is where a low-sucrose diet may help.

Low-sucrose diets: Healthier for us all, including those with diabetes

Ironically, having SID can prompt you to better focus upon your overall metabolic health by embracing and adhering to a low-sucrose diet. Now, this is not to say that SID is good for you; in fact, failure to absorb dietary sucrose and starch can impact the absorption of other nutrients, as well as disrupt the normal hormonal regulation of gastrointestinal functions. So, having an inability to digest every sucrose-laden food you eat is certainly not a good nor pain-free experience.

However, cutting way back on sucrose does have health benefits, especially if you are at risk for or have prediabetes or diabetes. Diets high in sucrose and high-fructose corn syrup have been shown to bring on “detrimental changes in hepatic lipid, insulin sensitivity, and circulating lipids, lipoproteins and uric acid,” as stated in a 2021 parallel, double-blinded, NIH-funded study. In other words, sugar intake in total, sucrose included, is associated with the risk of developing diabetes and dying from heart disease. Furthermore, the risk of obesity rises from high-sucrose consumption, increasing the risks of those same disorders and even certain cancers, as well.

As we reviewed in our What Is Sucrose? report, less than 10% of calories per day should come from added sugars, according to the USDA’s Dietary Guidelines for Americans 2020–2025. The World Health Organization (WHO) takes their sugar reduction recommendation even further, suggesting that we all reduce intake to 5% of total calories to improve glucose tolerance and decrease the prevalence of diabetes and the metabolic derangements that often precede and accompany it. “Reducing the intake of added sugars could translate to reduced diabetes-related morbidity and premature mortality for populations,” chimes in the Mayo Clinic. Yet, for American adults, added sugars account for almost 270 calories — or more than 13% — of total calories consumed per day. 

What does a low-sucrose diet look like?

No one, even those with SID, should attempt to skip consumption of carbohydrates (such as sucrose) altogether, as a minimum quantity of carbohydrates are necessary to supply glucose to the brain and provide energy to cells around the body.

However, according to the American Heart Association (AHA), the body does not need any added sugar to function healthily. Thus, reducing sucrose consumption to a low level can be a healthy decision for many individuals; (but consult with your medical provider first).

Emphasize consumption of natural sucrose sources, like vegetables and whole fruits, especially those containing other important substances such as vitamins, minerals, even proteins and healthy fats. See What Is Sucrose? for a complete list of whole foods (many fruits, vegetables, dairy products, and grains) that naturally contain sucrose. 

Some natural sucrose foods are lower in sucrose than others. For example, apricots, oranges, pineapples, and peaches each show sucrose as being the dominant sugar form contained within, meaning that more than 50% of total sugar is sucrose, not free fructose nor free glucose. By contrast, pears, apples, bananas and grapes contain much less sucrose per gram of total sugar than those previous fruits. See how fruits and vegetables compare in this way by checking the Canadian Sugar Institute’s list comparing the relative quantities of sucrose per 100 grams of many commonly eaten fruits and vegetables; we showcase this chart in the aforementioned What Is Sucrose? report.

The sucrose sources we should all try to avoid are the “processed” foods that contain added sucrose. Here are some primary examples of high-sucrose processed foods: 

• White bread
• Soda
• Ice cream
• Cookies
• Cake
• Fruit juice

Key Takeaways

Sucrose intolerance (SID) is an uncomfortable gastrointestinal disorder that often goes undiagnosed, but can be managed when found. In addition to trying a prescribed enzyme supplement, SID sufferers are often urged to follow a low-sucrose diet — which actually would benefit all of us, especially those at risk for diabetes or already managing prediabetes or diabetes. However, consult with your own medical team before making important food consumption choices.