What is sucrase-isomaltase?
Sucrase-isomaltase is an enzyme made in the small intestine that helps digest certain carbohydrates, such as sucrose and starches.
What are sucrose and starches?
Sucrose and starches make up more than 60% of the carbs eaten in Western diets.2
- Sucrose, sometimes referred to as ‘table sugar,’ is a disaccharide composed of fructose and glucose (two monosaccharides) and requires the enzyme sucrase for digestion.
- Dietary starch is a broad group of carbohydrates known as polysaccharides. Starches require several digestive enzymes during the digestive process in order to be properly digested. This begins in the mouth by an enzyme called amylase. 3Amylase breaks down starches into smaller chains of sugar molecules, such as the as maltose or alpha dextrins. From here, these sugar molecules get further broken down by enzymes like isomaltase.2
What is sucrase-isomaltase deficiency (SID)?
What causes SID?
SID is usually discussed as either being congenital/genetic or acquired.
- The genetic version is because of genetic variations in what are called ‘sucrase-isomaltase (SI) genes.’ 2There are at least 37 mutations in the SI gene found so far. The mutations affect gene functioning in different ways which results in a broad range of enzyme activity levels. For example, sucrase activity in patients with SID can be anywhere from absent to low, while isomaltase activity can range from absent to normal. Maltase activity can also be affected.51
- The acquired version of SID develops after some kind of intestinal damage, like infections (ex: Giardiasis), SIBO, Crohn’s disease, ulcerative colitis, etc. This version of SID can resolve once the secondary cause (like SIBO or Crohns) is cured or under control, whereas SID from a genetic variation is lifelong. Unfortunately, the acquired form of SID has not been extensively researched.52
What are the symptoms of SID?
Since enzyme activity can vary from person to person, symptoms and their severity can also vary.
Other factors that can affect symptoms are bacteria fermentation in the colon, coexisting abnormal gut motility, and visceral hypersensitivity, to name a few.2
How do you diagnose sucrase-isomaltase deficiency?
Diagnosing SID can be done by a few different testing methods. Some of these methods include breath tests, genetic testing, or a biopsy (which is the gold standard for diagnosing).2
If you want to learn more, check out our guide to IBS tests.
IBS & Sucrase-Isomaltase Deficiency
Symptom overlap & diagnostic confusion
IBS patients have higher rate of SI gene variants
Low FODMAP diet vs sucrose & starches
Sucrose and some starches are generally allowed on a Low FODMAP diet (a diet used to treat IBS).
Patients with IBS-D and SI gene variants have demonstrated less symptom relief from a low FODMAP diet than patients with IBS-D who do not have SI gene variants.
So for someone who has IBS and doesn’t respond to a low FODMAP diet, they may want to consider trialing SID diet interventions.2
Researchers still don’t know if patients with SID are misdiagnosed with IBS or if sucrose/starch are triggers for GI symptoms in patients with IBS. It’s possible that sucrose and starch may have similar clinical consequences as FODMAPs in IBS patients. 2As always, much more research is needed.
How To Treat Sucrase-Isomaltase Deficiency
Restrict foods with sucrose
Managing SID generally involves restricting foods that contain sucrose and, sometimes, starches. Since all forms of SID have impaired sucrase activity it is recommended to eliminate sucrose-containing foods first.
Sucrose naturally occurs in some foods, but is most well known for being ‘table sugar.’ So when avoiding sucrose, it’d be best to avoid anything with ‘added sugar,’ but commonly eaten fruits and vegetables may also need to be avoided.5
Decrease foods with starches
List of foods high in sucrose and starch
Unfortunately, food databases can sometimes lack adequate nutritional information on nutrients that aren’t mandated for food labels (ex: starches), but Sucraid™, a company that sells a digestive enzyme for SID management, has compiled food lists to help guide patients with SID.
For sucrose and starch content of food and how to read food label packages for SID diet restrictions, click these links:
Try digestive enzymes supplements
Another option for symptom management in SID is enzyme supplementation. Some patients supplement their meals with sacrosidase, a manufactured enzyme made from yeast that can aid in the digestion of sucrose.
Several studies have shown that taking sacrosidase (Sucraid™) following a meal with sucrose has been shown to reduce GI symptoms and improve breath testing results in patients with the genetic form of SID.
Keep in mind that supplementing with sacrosidase is not as effective when eating starch, as sacrosidase aims to assist in digesting sucrose. 2Additionally, supplementing sacrosidase has not been tested in patients with the acquired form of SID.
Chew more thoroughly
The takeaway from this research
Some patients with SID may find relief with either dietary interventions or enzyme supplementation alone, the most relief may be seen when combining the two interventions.2
The process of dietary restriction is complex and can involve several weeks of eliminating sources of sucrose and starches, followed by a gradual reintroduction of these foods into your diet. Because of this complexity, we recommend that any dietary restriction is under the guidance of a registered dietitian to ensure proper nutrition intake and successful symptom relief.